sys/vfs/hammer: Fix and add comments on root inode

[dragonfly.git] / sys / vfs / hammer / hammer_inode.c

/*
 * Copyright (c) 2007-2008 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "hammer.h"
#include <vm/vm_extern.h>

static int      hammer_unload_inode(struct hammer_inode *ip);
static void     hammer_free_inode(hammer_inode_t ip);
static void     hammer_flush_inode_core(hammer_inode_t ip,
                                        hammer_flush_group_t flg, int flags);
static int      hammer_setup_child_callback(hammer_record_t rec, void *data);
#if 0
static int      hammer_syncgrp_child_callback(hammer_record_t rec, void *data);
#endif
static int      hammer_setup_parent_inodes(hammer_inode_t ip, int depth,
                                        hammer_flush_group_t flg);
static int      hammer_setup_parent_inodes_helper(hammer_record_t record,
                                        int depth, hammer_flush_group_t flg);
static void     hammer_inode_wakereclaims(hammer_inode_t ip);
static struct hammer_inostats *hammer_inode_inostats(hammer_mount_t hmp,
                                        pid_t pid);

#ifdef DEBUG_TRUNCATE
extern struct hammer_inode *HammerTruncIp;
#endif

struct krate hammer_gen_krate = { 1 };

/*
 * RB-Tree support for inode structures
 */
int
hammer_ino_rb_compare(hammer_inode_t ip1, hammer_inode_t ip2)
{
        if (ip1->obj_localization < ip2->obj_localization)
                return(-1);
        if (ip1->obj_localization > ip2->obj_localization)
                return(1);
        if (ip1->obj_id < ip2->obj_id)
                return(-1);
        if (ip1->obj_id > ip2->obj_id)
                return(1);
        if (ip1->obj_asof < ip2->obj_asof)
                return(-1);
        if (ip1->obj_asof > ip2->obj_asof)
                return(1);
        return(0);
}

int
hammer_redo_rb_compare(hammer_inode_t ip1, hammer_inode_t ip2)
{
        if (ip1->redo_fifo_start < ip2->redo_fifo_start)
                return(-1);
        if (ip1->redo_fifo_start > ip2->redo_fifo_start)
                return(1);
        return(0);
}

/*
 * RB-Tree support for inode structures / special LOOKUP_INFO
 */
static int
hammer_inode_info_cmp(hammer_inode_info_t info, hammer_inode_t ip)
{
        if (info->obj_localization < ip->obj_localization)
                return(-1);
        if (info->obj_localization > ip->obj_localization)
                return(1);
        if (info->obj_id < ip->obj_id)
                return(-1);
        if (info->obj_id > ip->obj_id)
                return(1);
        if (info->obj_asof < ip->obj_asof)
                return(-1);
        if (info->obj_asof > ip->obj_asof)
                return(1);
        return(0);
}

/*
 * Used by hammer_scan_inode_snapshots() to locate all of an object's
 * snapshots.  Note that the asof field is not tested, which we can get
 * away with because it is the lowest-priority field.
 */
static int
hammer_inode_info_cmp_all_history(hammer_inode_t ip, void *data)
{
        hammer_inode_info_t info = data;

        if (ip->obj_localization > info->obj_localization)
                return(1);
        if (ip->obj_localization < info->obj_localization)
                return(-1);
        if (ip->obj_id > info->obj_id)
                return(1);
        if (ip->obj_id < info->obj_id)
                return(-1);
        return(0);
}

/*
 * Used by hammer_unload_pseudofs() to locate all inodes associated with
 * a particular PFS.
 */
static int
hammer_inode_pfs_cmp(hammer_inode_t ip, void *data)
{
        u_int32_t localization = *(u_int32_t *)data;
        if (ip->obj_localization > localization)
                return(1);
        if (ip->obj_localization < localization)
                return(-1);
        return(0);
}

/*
 * RB-Tree support for pseudofs structures
 */
static int
hammer_pfs_rb_compare(hammer_pseudofs_inmem_t p1, hammer_pseudofs_inmem_t p2)
{
        if (p1->localization < p2->localization)
                return(-1);
        if (p1->localization > p2->localization)
                return(1);
        return(0);
}


RB_GENERATE(hammer_ino_rb_tree, hammer_inode, rb_node, hammer_ino_rb_compare);
RB_GENERATE_XLOOKUP(hammer_ino_rb_tree, INFO, hammer_inode, rb_node,
                hammer_inode_info_cmp, hammer_inode_info_t);
RB_GENERATE2(hammer_pfs_rb_tree, hammer_pseudofs_inmem, rb_node,
             hammer_pfs_rb_compare, u_int32_t, localization);

/*
 * The kernel is not actively referencing this vnode but is still holding
 * it cached.
 *
 * This is called from the frontend.
 *
 * MPALMOSTSAFE
 */
int
hammer_vop_inactive(struct vop_inactive_args *ap)
{
        struct hammer_inode *ip = VTOI(ap->a_vp);
        hammer_mount_t hmp;

        /*
         * Degenerate case
         */
        if (ip == NULL) {
                vrecycle(ap->a_vp);
                return(0);
        }

        /*
         * If the inode no longer has visibility in the filesystem try to
         * recycle it immediately, even if the inode is dirty.  Recycling
         * it quickly allows the system to reclaim buffer cache and VM
         * resources which can matter a lot in a heavily loaded system.
         *
         * This can deadlock in vfsync() if we aren't careful.
         * 
         * Do not queue the inode to the flusher if we still have visibility,
         * otherwise namespace calls such as chmod will unnecessarily generate
         * multiple inode updates.
         */
        if (ip->ino_data.nlinks == 0) {
                hmp = ip->hmp;
                lwkt_gettoken(&hmp->fs_token);
                hammer_inode_unloadable_check(ip, 0);
                if (ip->flags & HAMMER_INODE_MODMASK)
                        hammer_flush_inode(ip, 0);
                lwkt_reltoken(&hmp->fs_token);
                vrecycle(ap->a_vp);
        }
        return(0);
}

/*
 * Release the vnode association.  This is typically (but not always)
 * the last reference on the inode.
 *
 * Once the association is lost we are on our own with regards to
 * flushing the inode.
 *
 * We must interlock ip->vp so hammer_get_vnode() can avoid races.
 */
int
hammer_vop_reclaim(struct vop_reclaim_args *ap)
{
        struct hammer_inode *ip;
        hammer_mount_t hmp;
        struct vnode *vp;

        vp = ap->a_vp;

        if ((ip = vp->v_data) != NULL) {
                hmp = ip->hmp;
                lwkt_gettoken(&hmp->fs_token);
                hammer_lock_ex(&ip->lock);
                vp->v_data = NULL;
                ip->vp = NULL;

                if ((ip->flags & HAMMER_INODE_RECLAIM) == 0) {
                        ++hammer_count_reclaims;
                        ++hmp->count_reclaims;
                        ip->flags |= HAMMER_INODE_RECLAIM;
                }
                hammer_unlock(&ip->lock);
                vclrisdirty(vp);
                hammer_rel_inode(ip, 1);
                lwkt_reltoken(&hmp->fs_token);
        }
        return(0);
}

/*
 * Inform the kernel that the inode is dirty.  This will be checked
 * by vn_unlock().
 *
 * Theoretically in order to reclaim a vnode the hammer_vop_reclaim()
 * must be called which will interlock against our inode lock, so
 * if VRECLAIMED is not set vp->v_mount (as used by vsetisdirty())
 * should be stable without having to acquire any new locks.
 */
void
hammer_inode_dirty(struct hammer_inode *ip)
{
        struct vnode *vp;

        if ((ip->flags & HAMMER_INODE_MODMASK) &&
            (vp = ip->vp) != NULL &&
            (vp->v_flag & (VRECLAIMED | VISDIRTY)) == 0) {
                vsetisdirty(vp);
        }
}

/*
 * Return a locked vnode for the specified inode.  The inode must be
 * referenced but NOT LOCKED on entry and will remain referenced on
 * return.
 *
 * Called from the frontend.
 */
int
hammer_get_vnode(struct hammer_inode *ip, struct vnode **vpp)
{
        hammer_mount_t hmp;
        struct vnode *vp;
        int error = 0;
        u_int8_t obj_type;

        hmp = ip->hmp;

        for (;;) {
                if ((vp = ip->vp) == NULL) {
                        error = getnewvnode(VT_HAMMER, hmp->mp, vpp, 0, 0);
                        if (error)
                                break;
                        hammer_lock_ex(&ip->lock);
                        if (ip->vp != NULL) {
                                hammer_unlock(&ip->lock);
                                vp = *vpp;
                                vp->v_type = VBAD;
                                vx_put(vp);
                                continue;
                        }
                        hammer_ref(&ip->lock);
                        vp = *vpp;
                        ip->vp = vp;

                        obj_type = ip->ino_data.obj_type;
                        vp->v_type = hammer_get_vnode_type(obj_type);

                        hammer_inode_wakereclaims(ip);

                        switch(ip->ino_data.obj_type) {
                        case HAMMER_OBJTYPE_CDEV:
                        case HAMMER_OBJTYPE_BDEV:
                                vp->v_ops = &hmp->mp->mnt_vn_spec_ops;
                                addaliasu(vp, ip->ino_data.rmajor,
                                          ip->ino_data.rminor);
                                break;
                        case HAMMER_OBJTYPE_FIFO:
                                vp->v_ops = &hmp->mp->mnt_vn_fifo_ops;
                                break;
                        case HAMMER_OBJTYPE_REGFILE:
                                break;
                        default:
                                break;
                        }

                        /*
                         * Only mark as the root vnode if the ip is not
                         * historical, otherwise the VFS cache will get
                         * confused.  The other half of the special handling
                         * is in hammer_vop_nlookupdotdot().
                         *
                         * Pseudo-filesystem roots can be accessed via
                         * non-root filesystem paths and setting VROOT may
                         * confuse the namecache.  Set VPFSROOT instead.
                         */
                        if (ip->obj_id == HAMMER_OBJID_ROOT &&
                            ip->obj_asof == hmp->asof) {
                                if (ip->obj_localization == 0)
                                        vsetflags(vp, VROOT);
                                else
                                        vsetflags(vp, VPFSROOT);
                        }

                        vp->v_data = (void *)ip;
                        /* vnode locked by getnewvnode() */
                        /* make related vnode dirty if inode dirty? */
                        hammer_unlock(&ip->lock);
                        if (vp->v_type == VREG) {
                                vinitvmio(vp, ip->ino_data.size,
                                          hammer_blocksize(ip->ino_data.size),
                                          hammer_blockoff(ip->ino_data.size));
                        }
                        break;
                }

                /*
                 * Interlock vnode clearing.  This does not prevent the
                 * vnode from going into a reclaimed state but it does
                 * prevent it from being destroyed or reused so the vget()
                 * will properly fail.
                 */
                hammer_lock_ex(&ip->lock);
                if ((vp = ip->vp) == NULL) {
                        hammer_unlock(&ip->lock);
                        continue;
                }
                vhold(vp);
                hammer_unlock(&ip->lock);

                /*
                 * loop if the vget fails (aka races), or if the vp
                 * no longer matches ip->vp.
                 */
                if (vget(vp, LK_EXCLUSIVE) == 0) {
                        if (vp == ip->vp) {
                                vdrop(vp);
                                break;
                        }
                        vput(vp);
                }
                vdrop(vp);
        }
        *vpp = vp;
        return(error);
}

/*
 * Locate all copies of the inode for obj_id compatible with the specified
 * asof, reference, and issue the related call-back.  This routine is used
 * for direct-io invalidation and does not create any new inodes.
 */
void
hammer_scan_inode_snapshots(hammer_mount_t hmp, hammer_inode_info_t iinfo,
                            int (*callback)(hammer_inode_t ip, void *data),
                            void *data)
{
        hammer_ino_rb_tree_RB_SCAN(&hmp->rb_inos_root,
                                   hammer_inode_info_cmp_all_history,
                                   callback, iinfo);
}

/*
 * Acquire a HAMMER inode.  The returned inode is not locked.  These functions
 * do not attach or detach the related vnode (use hammer_get_vnode() for
 * that).
 *
 * The flags argument is only applied for newly created inodes, and only
 * certain flags are inherited.
 *
 * Called from the frontend.
 */
struct hammer_inode *
hammer_get_inode(hammer_transaction_t trans, hammer_inode_t dip,
                 int64_t obj_id, hammer_tid_t asof, u_int32_t localization,
                 int flags, int *errorp)
{
        hammer_mount_t hmp = trans->hmp;
        struct hammer_node_cache *cachep;
        struct hammer_inode_info iinfo;
        struct hammer_cursor cursor;
        struct hammer_inode *ip;


        /*
         * Determine if we already have an inode cached.  If we do then
         * we are golden.
         *
         * If we find an inode with no vnode we have to mark the
         * transaction such that hammer_inode_waitreclaims() is
         * called later on to avoid building up an infinite number
         * of inodes.  Otherwise we can continue to * add new inodes
         * faster then they can be disposed of, even with the tsleep
         * delay.
         *
         * If we find a dummy inode we return a failure so dounlink
         * (which does another lookup) doesn't try to mess with the
         * link count.  hammer_vop_nresolve() uses hammer_get_dummy_inode()
         * to ref dummy inodes.
         */
        iinfo.obj_id = obj_id;
        iinfo.obj_asof = asof;
        iinfo.obj_localization = localization;
loop:
        ip = hammer_ino_rb_tree_RB_LOOKUP_INFO(&hmp->rb_inos_root, &iinfo);
        if (ip) {
                if (ip->flags & HAMMER_INODE_DUMMY) {
                        *errorp = ENOENT;
                        return(NULL);
                }
                hammer_ref(&ip->lock);
                *errorp = 0;
                return(ip);
        }

        /*
         * Allocate a new inode structure and deal with races later.
         */
        ip = kmalloc(sizeof(*ip), hmp->m_inodes, M_WAITOK|M_ZERO);
        ++hammer_count_inodes;
        ++hmp->count_inodes;
        ip->obj_id = obj_id;
        ip->obj_asof = iinfo.obj_asof;
        ip->obj_localization = localization;
        ip->hmp = hmp;
        ip->flags = flags & HAMMER_INODE_RO;
        ip->cache[0].ip = ip;
        ip->cache[1].ip = ip;
        ip->cache[2].ip = ip;
        ip->cache[3].ip = ip;
        if (hmp->ronly)
                ip->flags |= HAMMER_INODE_RO;
        ip->sync_trunc_off = ip->trunc_off = ip->save_trunc_off =
                0x7FFFFFFFFFFFFFFFLL;
        RB_INIT(&ip->rec_tree);
        TAILQ_INIT(&ip->target_list);
        hammer_ref(&ip->lock);

        /*
         * Locate the on-disk inode.  If this is a PFS root we always
         * access the current version of the root inode and (if it is not
         * a master) always access information under it with a snapshot
         * TID.
         *
         * We cache recent inode lookups in this directory in dip->cache[2].
         * If we can't find it we assume the inode we are looking for is
         * close to the directory inode.
         */
retry:
        cachep = NULL;
        if (dip) {
                if (dip->cache[2].node)
                        cachep = &dip->cache[2];
                else
                        cachep = &dip->cache[0];
        }
        hammer_init_cursor(trans, &cursor, cachep, NULL);
        cursor.key_beg.localization = localization + HAMMER_LOCALIZE_INODE;
        cursor.key_beg.obj_id = ip->obj_id;
        cursor.key_beg.key = 0;
        cursor.key_beg.create_tid = 0;
        cursor.key_beg.delete_tid = 0;
        cursor.key_beg.rec_type = HAMMER_RECTYPE_INODE;
        cursor.key_beg.obj_type = 0;

        cursor.asof = iinfo.obj_asof;
        cursor.flags = HAMMER_CURSOR_GET_LEAF | HAMMER_CURSOR_GET_DATA |
                       HAMMER_CURSOR_ASOF;

        *errorp = hammer_btree_lookup(&cursor);
        if (*errorp == EDEADLK) {
                hammer_done_cursor(&cursor);
                goto retry;
        }

        /*
         * On success the B-Tree lookup will hold the appropriate
         * buffer cache buffers and provide a pointer to the requested
         * information.  Copy the information to the in-memory inode
         * and cache the B-Tree node to improve future operations.
         */
        if (*errorp == 0) {
                ip->ino_leaf = cursor.node->ondisk->elms[cursor.index].leaf;
                ip->ino_data = cursor.data->inode;

                /*
                 * cache[0] tries to cache the location of the object inode.
                 * The assumption is that it is near the directory inode.
                 *
                 * cache[1] tries to cache the location of the object data.
                 * We might have something in the governing directory from
                 * scan optimizations (see the strategy code in
                 * hammer_vnops.c).
                 *
                 * We update dip->cache[2], if possible, with the location
                 * of the object inode for future directory shortcuts.
                 */
                hammer_cache_node(&ip->cache[0], cursor.node);
                if (dip) {
                        if (dip->cache[3].node) {
                                hammer_cache_node(&ip->cache[1],
                                                  dip->cache[3].node);
                        }
                        hammer_cache_node(&dip->cache[2], cursor.node);
                }

                /*
                 * The file should not contain any data past the file size
                 * stored in the inode.  Setting save_trunc_off to the
                 * file size instead of max reduces B-Tree lookup overheads
                 * on append by allowing the flusher to avoid checking for
                 * record overwrites.
                 */
                ip->save_trunc_off = ip->ino_data.size;

                /*
                 * Locate and assign the pseudofs management structure to
                 * the inode.
                 */
                if (dip && dip->obj_localization == ip->obj_localization) {
                        ip->pfsm = dip->pfsm;
                        hammer_ref(&ip->pfsm->lock);
                } else {
                        ip->pfsm = hammer_load_pseudofs(trans,
                                                        ip->obj_localization,
                                                        errorp);
                        *errorp = 0;    /* ignore ENOENT */
                }
        }

        /*
         * The inode is placed on the red-black tree and will be synced to
         * the media when flushed or by the filesystem sync.  If this races
         * another instantiation/lookup the insertion will fail.
         */
        if (*errorp == 0) {
                if (RB_INSERT(hammer_ino_rb_tree, &hmp->rb_inos_root, ip)) {
                        hammer_free_inode(ip);
                        hammer_done_cursor(&cursor);
                        goto loop;
                }
                ip->flags |= HAMMER_INODE_ONDISK;
        } else {
                if (ip->flags & HAMMER_INODE_RSV_INODES) {
                        ip->flags &= ~HAMMER_INODE_RSV_INODES; /* sanity */
                        --hmp->rsv_inodes;
                }

                hammer_free_inode(ip);
                ip = NULL;
        }
        hammer_done_cursor(&cursor);

        /*
         * NEWINODE is only set if the inode becomes dirty later,
         * setting it here just leads to unnecessary stalls.
         *
         * trans->flags |= HAMMER_TRANSF_NEWINODE;
         */
        return (ip);
}

/*
 * Get a dummy inode to placemark a broken directory entry.
 */
struct hammer_inode *
hammer_get_dummy_inode(hammer_transaction_t trans, hammer_inode_t dip,
                 int64_t obj_id, hammer_tid_t asof, u_int32_t localization,
                 int flags, int *errorp)
{
        hammer_mount_t hmp = trans->hmp;
        struct hammer_inode_info iinfo;
        struct hammer_inode *ip;

        /*
         * Determine if we already have an inode cached.  If we do then
         * we are golden.
         *
         * If we find an inode with no vnode we have to mark the
         * transaction such that hammer_inode_waitreclaims() is
         * called later on to avoid building up an infinite number
         * of inodes.  Otherwise we can continue to * add new inodes
         * faster then they can be disposed of, even with the tsleep
         * delay.
         *
         * If we find a non-fake inode we return an error.  Only fake
         * inodes can be returned by this routine.
         */
        iinfo.obj_id = obj_id;
        iinfo.obj_asof = asof;
        iinfo.obj_localization = localization;
loop:
        *errorp = 0;
        ip = hammer_ino_rb_tree_RB_LOOKUP_INFO(&hmp->rb_inos_root, &iinfo);
        if (ip) {
                if ((ip->flags & HAMMER_INODE_DUMMY) == 0) {
                        *errorp = ENOENT;
                        return(NULL);
                }
                hammer_ref(&ip->lock);
                return(ip);
        }

        /*
         * Allocate a new inode structure and deal with races later.
         */
        ip = kmalloc(sizeof(*ip), hmp->m_inodes, M_WAITOK|M_ZERO);
        ++hammer_count_inodes;
        ++hmp->count_inodes;
        ip->obj_id = obj_id;
        ip->obj_asof = iinfo.obj_asof;
        ip->obj_localization = localization;
        ip->hmp = hmp;
        ip->flags = flags | HAMMER_INODE_RO | HAMMER_INODE_DUMMY;
        ip->cache[0].ip = ip;
        ip->cache[1].ip = ip;
        ip->cache[2].ip = ip;
        ip->cache[3].ip = ip;
        ip->sync_trunc_off = ip->trunc_off = ip->save_trunc_off =
                0x7FFFFFFFFFFFFFFFLL;
        RB_INIT(&ip->rec_tree);
        TAILQ_INIT(&ip->target_list);
        hammer_ref(&ip->lock);

        /*
         * Populate the dummy inode.  Leave everything zero'd out.
         *
         * (ip->ino_leaf and ip->ino_data)
         *
         * Make the dummy inode a FIFO object which most copy programs
         * will properly ignore.
         */
        ip->save_trunc_off = ip->ino_data.size;
        ip->ino_data.obj_type = HAMMER_OBJTYPE_FIFO;

        /*
         * Locate and assign the pseudofs management structure to
         * the inode.
         */
        if (dip && dip->obj_localization == ip->obj_localization) {
                ip->pfsm = dip->pfsm;
                hammer_ref(&ip->pfsm->lock);
        } else {
                ip->pfsm = hammer_load_pseudofs(trans, ip->obj_localization,
                                                errorp);
                *errorp = 0;    /* ignore ENOENT */
        }

        /*
         * The inode is placed on the red-black tree and will be synced to
         * the media when flushed or by the filesystem sync.  If this races
         * another instantiation/lookup the insertion will fail.
         *
         * NOTE: Do not set HAMMER_INODE_ONDISK.  The inode is a fake.
         */
        if (*errorp == 0) {
                if (RB_INSERT(hammer_ino_rb_tree, &hmp->rb_inos_root, ip)) {
                        hammer_free_inode(ip);
                        goto loop;
                }
        } else {
                if (ip->flags & HAMMER_INODE_RSV_INODES) {
                        ip->flags &= ~HAMMER_INODE_RSV_INODES; /* sanity */
                        --hmp->rsv_inodes;
                }
                hammer_free_inode(ip);
                ip = NULL;
        }
        trans->flags |= HAMMER_TRANSF_NEWINODE;
        return (ip);
}

/*
 * Return a referenced inode only if it is in our inode cache.
 *
 * Dummy inodes do not count.
 */
struct hammer_inode *
hammer_find_inode(hammer_transaction_t trans, int64_t obj_id,
                  hammer_tid_t asof, u_int32_t localization)
{
        hammer_mount_t hmp = trans->hmp;
        struct hammer_inode_info iinfo;
        struct hammer_inode *ip;

        iinfo.obj_id = obj_id;
        iinfo.obj_asof = asof;
        iinfo.obj_localization = localization;

        ip = hammer_ino_rb_tree_RB_LOOKUP_INFO(&hmp->rb_inos_root, &iinfo);
        if (ip) {
                if (ip->flags & HAMMER_INODE_DUMMY)
                        ip = NULL;
                else
                        hammer_ref(&ip->lock);
        }
        return(ip);
}

/*
 * Create a new filesystem object, returning the inode in *ipp.  The
 * returned inode will be referenced.  The inode is created in-memory.
 *
 * If pfsm is non-NULL the caller wishes to create the root inode for
 * a master PFS.
 */
int
hammer_create_inode(hammer_transaction_t trans, struct vattr *vap,
                    struct ucred *cred,
                    hammer_inode_t dip, const char *name, int namelen,
                    hammer_pseudofs_inmem_t pfsm, struct hammer_inode **ipp)
{
        hammer_mount_t hmp;
        hammer_inode_t ip;
        uid_t xuid;
        int error;
        int64_t namekey;
        u_int32_t dummy;

        hmp = trans->hmp;

        /*
         * Disallow the creation of new inodes in directories which
         * have been deleted.  In HAMMER, this will cause a record
         * syncing assertion later on in the flush code.
         */
        if (dip && dip->ino_data.nlinks == 0) {
                *ipp = NULL;
                return (EINVAL);
        }

        /*
         * Allocate inode
         */
        ip = kmalloc(sizeof(*ip), hmp->m_inodes, M_WAITOK|M_ZERO);
        ++hammer_count_inodes;
        ++hmp->count_inodes;
        trans->flags |= HAMMER_TRANSF_NEWINODE;

        if (pfsm) {
                KKASSERT(pfsm->localization != 0);
                ip->obj_id = HAMMER_OBJID_ROOT;
                ip->obj_localization = pfsm->localization;
        } else {
                KKASSERT(dip != NULL);
                namekey = hammer_directory_namekey(dip, name, namelen, &dummy);
                ip->obj_id = hammer_alloc_objid(hmp, dip, namekey);
                ip->obj_localization = dip->obj_localization;
        }

        KKASSERT(ip->obj_id != 0);
        ip->obj_asof = hmp->asof;
        ip->hmp = hmp;
        ip->flush_state = HAMMER_FST_IDLE;
        ip->flags = HAMMER_INODE_DDIRTY |
                    HAMMER_INODE_ATIME | HAMMER_INODE_MTIME;
        ip->cache[0].ip = ip;
        ip->cache[1].ip = ip;
        ip->cache[2].ip = ip;
        ip->cache[3].ip = ip;

        ip->trunc_off = 0x7FFFFFFFFFFFFFFFLL;
        /* ip->save_trunc_off = 0; (already zero) */
        RB_INIT(&ip->rec_tree);
        TAILQ_INIT(&ip->target_list);

        ip->ino_data.atime = trans->time;
        ip->ino_data.mtime = trans->time;
        ip->ino_data.size = 0;
        ip->ino_data.nlinks = 0;

        /*
         * A nohistory designator on the parent directory is inherited by
         * the child.  We will do this even for pseudo-fs creation... the
         * sysad can turn it off.
         */
        if (dip) {
                ip->ino_data.uflags = dip->ino_data.uflags &
                                      (SF_NOHISTORY|UF_NOHISTORY|UF_NODUMP);
        }

        ip->ino_leaf.base.btype = HAMMER_BTREE_TYPE_RECORD;
        ip->ino_leaf.base.localization = ip->obj_localization +
                                         HAMMER_LOCALIZE_INODE;
        ip->ino_leaf.base.obj_id = ip->obj_id;
        ip->ino_leaf.base.key = 0;
        ip->ino_leaf.base.create_tid = 0;
        ip->ino_leaf.base.delete_tid = 0;
        ip->ino_leaf.base.rec_type = HAMMER_RECTYPE_INODE;
        ip->ino_leaf.base.obj_type = hammer_get_obj_type(vap->va_type);

        ip->ino_data.obj_type = ip->ino_leaf.base.obj_type;
        ip->ino_data.version = HAMMER_INODE_DATA_VERSION;
        ip->ino_data.mode = vap->va_mode;
        ip->ino_data.ctime = trans->time;

        /*
         * If we are running version 2 or greater directory entries are
         * inode-localized instead of data-localized.
         */
        if (trans->hmp->version >= HAMMER_VOL_VERSION_TWO) {
                if (ip->ino_leaf.base.obj_type == HAMMER_OBJTYPE_DIRECTORY) {
                        ip->ino_data.cap_flags |=
                                HAMMER_INODE_CAP_DIR_LOCAL_INO;
                }
        }
        if (trans->hmp->version >= HAMMER_VOL_VERSION_SIX) {
                if (ip->ino_leaf.base.obj_type == HAMMER_OBJTYPE_DIRECTORY) {
                        ip->ino_data.cap_flags |=
                                HAMMER_INODE_CAP_DIRHASH_ALG1;
                }
        }

        /*
         * Setup the ".." pointer.  This only needs to be done for directories
         * but we do it for all objects as a recovery aid.
         */
        if (dip)
                ip->ino_data.parent_obj_id = dip->ino_leaf.base.obj_id;
#if 0
        /*
         * The parent_obj_localization field only applies to pseudo-fs roots.
         * XXX this is no longer applicable, PFSs are no longer directly
         * tied into the parent's directory structure.
         */
        if (ip->ino_data.obj_type == HAMMER_OBJTYPE_DIRECTORY &&
            ip->obj_id == HAMMER_OBJID_ROOT) {
                ip->ino_data.ext.obj.parent_obj_localization = 
                                                dip->obj_localization;
        }
#endif

        switch(ip->ino_leaf.base.obj_type) {
        case HAMMER_OBJTYPE_CDEV:
        case HAMMER_OBJTYPE_BDEV:
                ip->ino_data.rmajor = vap->va_rmajor;
                ip->ino_data.rminor = vap->va_rminor;
                break;
        default:
                break;
        }

        /*
         * Calculate default uid/gid and overwrite with information from
         * the vap.
         */
        if (dip) {
                xuid = hammer_to_unix_xid(&dip->ino_data.uid);
                xuid = vop_helper_create_uid(hmp->mp, dip->ino_data.mode,
                                             xuid, cred, &vap->va_mode);
        } else {
                xuid = 0;
        }
        ip->ino_data.mode = vap->va_mode;

        if (vap->va_vaflags & VA_UID_UUID_VALID)
                ip->ino_data.uid = vap->va_uid_uuid;
        else if (vap->va_uid != (uid_t)VNOVAL)
                hammer_guid_to_uuid(&ip->ino_data.uid, vap->va_uid);
        else
                hammer_guid_to_uuid(&ip->ino_data.uid, xuid);

        if (vap->va_vaflags & VA_GID_UUID_VALID)
                ip->ino_data.gid = vap->va_gid_uuid;
        else if (vap->va_gid != (gid_t)VNOVAL)
                hammer_guid_to_uuid(&ip->ino_data.gid, vap->va_gid);
        else if (dip)
                ip->ino_data.gid = dip->ino_data.gid;

        hammer_ref(&ip->lock);

        if (pfsm) {
                ip->pfsm = pfsm;
                hammer_ref(&pfsm->lock);
                error = 0;
        } else if (dip->obj_localization == ip->obj_localization) {
                ip->pfsm = dip->pfsm;
                hammer_ref(&ip->pfsm->lock);
                error = 0;
        } else {
                ip->pfsm = hammer_load_pseudofs(trans,
                                                ip->obj_localization,
                                                &error);
                error = 0;      /* ignore ENOENT */
        }

        if (error) {
                hammer_free_inode(ip);
                ip = NULL;
        } else if (RB_INSERT(hammer_ino_rb_tree, &hmp->rb_inos_root, ip)) {
                panic("hammer_create_inode: duplicate obj_id %llx",
                      (long long)ip->obj_id);
                /* not reached */
                hammer_free_inode(ip);
        }
        *ipp = ip;
        return(error);
}

/*
 * Final cleanup / freeing of an inode structure
 */
static void
hammer_free_inode(hammer_inode_t ip)
{
        struct hammer_mount *hmp;

        hmp = ip->hmp;
        KKASSERT(hammer_oneref(&ip->lock));
        hammer_uncache_node(&ip->cache[0]);
        hammer_uncache_node(&ip->cache[1]);
        hammer_uncache_node(&ip->cache[2]);
        hammer_uncache_node(&ip->cache[3]);
        hammer_inode_wakereclaims(ip);
        if (ip->objid_cache)
                hammer_clear_objid(ip);
        --hammer_count_inodes;
        --hmp->count_inodes;
        if (ip->pfsm) {
                hammer_rel_pseudofs(hmp, ip->pfsm);
                ip->pfsm = NULL;
        }
        kfree(ip, hmp->m_inodes);
        ip = NULL;
}

/*
 * Retrieve pseudo-fs data.  NULL will never be returned.
 *
 * If an error occurs *errorp will be set and a default template is returned,
 * otherwise *errorp is set to 0.  Typically when an error occurs it will
 * be ENOENT.
 */
hammer_pseudofs_inmem_t
hammer_load_pseudofs(hammer_transaction_t trans,
                     u_int32_t localization, int *errorp)
{
        hammer_mount_t hmp = trans->hmp;
        hammer_inode_t ip;
        hammer_pseudofs_inmem_t pfsm;
        struct hammer_cursor cursor;
        int bytes;

retry:
        pfsm = RB_LOOKUP(hammer_pfs_rb_tree, &hmp->rb_pfsm_root, localization);
        if (pfsm) {
                hammer_ref(&pfsm->lock);
                *errorp = 0;
                return(pfsm);
        }

        /*
         * PFS records are associated with the root inode (not the PFS root
         * inode, but the real root).  Avoid an infinite recursion if loading
         * the PFS for the real root.
         */
        if (localization) {
                ip = hammer_get_inode(trans, NULL, HAMMER_OBJID_ROOT,
                                      HAMMER_MAX_TID,
                                      HAMMER_DEF_LOCALIZATION, 0, errorp);
        } else {
                ip = NULL;
        }

        pfsm = kmalloc(sizeof(*pfsm), hmp->m_misc, M_WAITOK | M_ZERO);
        pfsm->localization = localization;
        pfsm->pfsd.unique_uuid = trans->rootvol->ondisk->vol_fsid;
        pfsm->pfsd.shared_uuid = pfsm->pfsd.unique_uuid;

        hammer_init_cursor(trans, &cursor, (ip ? &ip->cache[1] : NULL), ip);
        cursor.key_beg.localization = HAMMER_DEF_LOCALIZATION +
                                      HAMMER_LOCALIZE_MISC;
        cursor.key_beg.obj_id = HAMMER_OBJID_ROOT;
        cursor.key_beg.create_tid = 0;
        cursor.key_beg.delete_tid = 0;
        cursor.key_beg.rec_type = HAMMER_RECTYPE_PFS;
        cursor.key_beg.obj_type = 0;
        cursor.key_beg.key = localization;
        cursor.asof = HAMMER_MAX_TID;
        cursor.flags |= HAMMER_CURSOR_ASOF;

        if (ip)
                *errorp = hammer_ip_lookup(&cursor);
        else
                *errorp = hammer_btree_lookup(&cursor);
        if (*errorp == 0) {
                *errorp = hammer_ip_resolve_data(&cursor);
                if (*errorp == 0) {
                        if (cursor.data->pfsd.mirror_flags &
                            HAMMER_PFSD_DELETED) {
                                *errorp = ENOENT;
                        } else {
                                bytes = cursor.leaf->data_len;
                                if (bytes > sizeof(pfsm->pfsd))
                                        bytes = sizeof(pfsm->pfsd);
                                bcopy(cursor.data, &pfsm->pfsd, bytes);
                        }
                }
        }
        hammer_done_cursor(&cursor);

        pfsm->fsid_udev = hammer_fsid_to_udev(&pfsm->pfsd.shared_uuid);
        hammer_ref(&pfsm->lock);
        if (ip)
                hammer_rel_inode(ip, 0);
        if (RB_INSERT(hammer_pfs_rb_tree, &hmp->rb_pfsm_root, pfsm)) {
                kfree(pfsm, hmp->m_misc);
                goto retry;
        }
        return(pfsm);
}

/*
 * Store pseudo-fs data.  The backend will automatically delete any prior
 * on-disk pseudo-fs data but we have to delete in-memory versions.
 */
int
hammer_save_pseudofs(hammer_transaction_t trans, hammer_pseudofs_inmem_t pfsm)
{
        struct hammer_cursor cursor;
        hammer_record_t record;
        hammer_inode_t ip;
        int error;

        /*
         * PFS records are associated with the root inode (not the PFS root
         * inode, but the real root).
         */
        ip = hammer_get_inode(trans, NULL, HAMMER_OBJID_ROOT, HAMMER_MAX_TID,
                              HAMMER_DEF_LOCALIZATION, 0, &error);
retry:
        pfsm->fsid_udev = hammer_fsid_to_udev(&pfsm->pfsd.shared_uuid);
        hammer_init_cursor(trans, &cursor, &ip->cache[1], ip);
        cursor.key_beg.localization = ip->obj_localization +
                                      HAMMER_LOCALIZE_MISC;
        cursor.key_beg.obj_id = HAMMER_OBJID_ROOT;
        cursor.key_beg.create_tid = 0;
        cursor.key_beg.delete_tid = 0;
        cursor.key_beg.rec_type = HAMMER_RECTYPE_PFS;
        cursor.key_beg.obj_type = 0;
        cursor.key_beg.key = pfsm->localization;
        cursor.asof = HAMMER_MAX_TID;
        cursor.flags |= HAMMER_CURSOR_ASOF;

        /*
         * Replace any in-memory version of the record.
         */
        error = hammer_ip_lookup(&cursor);
        if (error == 0 && hammer_cursor_inmem(&cursor)) {
                record = cursor.iprec;
                if (record->flags & HAMMER_RECF_INTERLOCK_BE) {
                        KKASSERT(cursor.deadlk_rec == NULL);
                        hammer_ref(&record->lock);
                        cursor.deadlk_rec = record;
                        error = EDEADLK;
                } else {
                        record->flags |= HAMMER_RECF_DELETED_FE;
                        error = 0;
                }
        }

        /*
         * Allocate replacement general record.  The backend flush will
         * delete any on-disk version of the record.
         */
        if (error == 0 || error == ENOENT) {
                record = hammer_alloc_mem_record(ip, sizeof(pfsm->pfsd));
                record->type = HAMMER_MEM_RECORD_GENERAL;

                record->leaf.base.localization = ip->obj_localization +
                                                 HAMMER_LOCALIZE_MISC;
                record->leaf.base.rec_type = HAMMER_RECTYPE_PFS;
                record->leaf.base.key = pfsm->localization;
                record->leaf.data_len = sizeof(pfsm->pfsd);
                bcopy(&pfsm->pfsd, record->data, sizeof(pfsm->pfsd));
                error = hammer_ip_add_record(trans, record);
        }
        hammer_done_cursor(&cursor);
        if (error == EDEADLK)
                goto retry;
        hammer_rel_inode(ip, 0);
        return(error);
}

/*
 * Create a root directory for a PFS if one does not alredy exist.
 *
 * The PFS root stands alone so we must also bump the nlinks count
 * to prevent it from being destroyed on release.
 */
int
hammer_mkroot_pseudofs(hammer_transaction_t trans, struct ucred *cred,
                       hammer_pseudofs_inmem_t pfsm)
{
        hammer_inode_t ip;
        struct vattr vap;
        int error;

        ip = hammer_get_inode(trans, NULL, HAMMER_OBJID_ROOT, HAMMER_MAX_TID,
                              pfsm->localization, 0, &error);
        if (ip == NULL) {
                vattr_null(&vap);
                vap.va_mode = 0755;
                vap.va_type = VDIR;
                error = hammer_create_inode(trans, &vap, cred,
                                            NULL, NULL, 0,
                                            pfsm, &ip);
                if (error == 0) {
                        ++ip->ino_data.nlinks;
                        hammer_modify_inode(trans, ip, HAMMER_INODE_DDIRTY);
                }
        }
        if (ip)
                hammer_rel_inode(ip, 0);
        return(error);
}

/*
 * Unload any vnodes & inodes associated with a PFS, return ENOTEMPTY
 * if we are unable to disassociate all the inodes.
 */
static
int
hammer_unload_pseudofs_callback(hammer_inode_t ip, void *data)
{
        int res;

        hammer_ref(&ip->lock);
        if (hammer_isactive(&ip->lock) == 2 && ip->vp)
                vclean_unlocked(ip->vp);
        if (hammer_isactive(&ip->lock) == 1 && ip->vp == NULL)
                res = 0;
        else
                res = -1;       /* stop, someone is using the inode */
        hammer_rel_inode(ip, 0);
        return(res);
}

int
hammer_unload_pseudofs(hammer_transaction_t trans, u_int32_t localization)
{
        int res;
        int try;

        for (try = res = 0; try < 4; ++try) {
                res = hammer_ino_rb_tree_RB_SCAN(&trans->hmp->rb_inos_root,
                                           hammer_inode_pfs_cmp,
                                           hammer_unload_pseudofs_callback,
                                           &localization);
                if (res == 0 && try > 1)
                        break;
                hammer_flusher_sync(trans->hmp);
        }
        if (res != 0)
                res = ENOTEMPTY;
        return(res);
}


/*
 * Release a reference on a PFS
 */
void
hammer_rel_pseudofs(hammer_mount_t hmp, hammer_pseudofs_inmem_t pfsm)
{
        hammer_rel(&pfsm->lock);
        if (hammer_norefs(&pfsm->lock)) {
                RB_REMOVE(hammer_pfs_rb_tree, &hmp->rb_pfsm_root, pfsm);
                kfree(pfsm, hmp->m_misc);
        }
}

/*
 * Called by hammer_sync_inode().
 */
static int
hammer_update_inode(hammer_cursor_t cursor, hammer_inode_t ip)
{
        hammer_transaction_t trans = cursor->trans;
        hammer_record_t record;
        int error;
        int redirty;

retry:
        error = 0;

        /*
         * If the inode has a presence on-disk then locate it and mark
         * it deleted, setting DELONDISK.
         *
         * The record may or may not be physically deleted, depending on
         * the retention policy.
         */
        if ((ip->flags & (HAMMER_INODE_ONDISK|HAMMER_INODE_DELONDISK)) ==
            HAMMER_INODE_ONDISK) {
                hammer_normalize_cursor(cursor);
                cursor->key_beg.localization = ip->obj_localization + 
                                               HAMMER_LOCALIZE_INODE;
                cursor->key_beg.obj_id = ip->obj_id;
                cursor->key_beg.key = 0;
                cursor->key_beg.create_tid = 0;
                cursor->key_beg.delete_tid = 0;
                cursor->key_beg.rec_type = HAMMER_RECTYPE_INODE;
                cursor->key_beg.obj_type = 0;
                cursor->asof = ip->obj_asof;
                cursor->flags &= ~HAMMER_CURSOR_INITMASK;
                cursor->flags |= HAMMER_CURSOR_GET_LEAF | HAMMER_CURSOR_ASOF;
                cursor->flags |= HAMMER_CURSOR_BACKEND;

                error = hammer_btree_lookup(cursor);
                if (hammer_debug_inode)
                        kprintf("IPDEL %p %08x %d", ip, ip->flags, error);

                if (error == 0) {
                        error = hammer_ip_delete_record(cursor, ip, trans->tid);
                        if (hammer_debug_inode)
                                kprintf(" error %d\n", error);
                        if (error == 0) {
                                ip->flags |= HAMMER_INODE_DELONDISK;
                        }
                        if (cursor->node)
                                hammer_cache_node(&ip->cache[0], cursor->node);
                }
                if (error == EDEADLK) {
                        hammer_done_cursor(cursor);
                        error = hammer_init_cursor(trans, cursor,
                                                   &ip->cache[0], ip);
                        if (hammer_debug_inode)
                                kprintf("IPDED %p %d\n", ip, error);
                        if (error == 0)
                                goto retry;
                }
        }

        /*
         * Ok, write out the initial record or a new record (after deleting
         * the old one), unless the DELETED flag is set.  This routine will
         * clear DELONDISK if it writes out a record.
         *
         * Update our inode statistics if this is the first application of
         * the inode on-disk.
         */
        if (error == 0 && (ip->flags & HAMMER_INODE_DELETED) == 0) {
                /*
                 * Generate a record and write it to the media.  We clean-up
                 * the state before releasing so we do not have to set-up
                 * a flush_group.
                 */
                record = hammer_alloc_mem_record(ip, 0);
                record->type = HAMMER_MEM_RECORD_INODE;
                record->flush_state = HAMMER_FST_FLUSH;
                record->leaf = ip->sync_ino_leaf;
                record->leaf.base.create_tid = trans->tid;
                record->leaf.data_len = sizeof(ip->sync_ino_data);
                record->leaf.create_ts = trans->time32;
                record->data = (void *)&ip->sync_ino_data;
                record->flags |= HAMMER_RECF_INTERLOCK_BE;

                /*
                 * If this flag is set we cannot sync the new file size
                 * because we haven't finished related truncations.  The
                 * inode will be flushed in another flush group to finish
                 * the job.
                 */
                if ((ip->flags & HAMMER_INODE_WOULDBLOCK) &&
                    ip->sync_ino_data.size != ip->ino_data.size) {
                        redirty = 1;
                        ip->sync_ino_data.size = ip->ino_data.size;
                } else {
                        redirty = 0;
                }

                for (;;) {
                        error = hammer_ip_sync_record_cursor(cursor, record);
                        if (hammer_debug_inode)
                                kprintf("GENREC %p rec %08x %d\n",      
                                        ip, record->flags, error);
                        if (error != EDEADLK)
                                break;
                        hammer_done_cursor(cursor);
                        error = hammer_init_cursor(trans, cursor,
                                                   &ip->cache[0], ip);
                        if (hammer_debug_inode)
                                kprintf("GENREC reinit %d\n", error);
                        if (error)
                                break;
                }

                /*
                 * Note:  The record was never on the inode's record tree
                 * so just wave our hands importantly and destroy it.
                 */
                record->flags |= HAMMER_RECF_COMMITTED;
                record->flags &= ~HAMMER_RECF_INTERLOCK_BE;
                record->flush_state = HAMMER_FST_IDLE;
                ++ip->rec_generation;
                hammer_rel_mem_record(record);

                /*
                 * Finish up.
                 */
                if (error == 0) {
                        if (hammer_debug_inode)
                                kprintf("CLEANDELOND %p %08x\n", ip, ip->flags);
                        ip->sync_flags &= ~(HAMMER_INODE_DDIRTY |
                                            HAMMER_INODE_SDIRTY |
                                            HAMMER_INODE_ATIME |
                                            HAMMER_INODE_MTIME);
                        ip->flags &= ~HAMMER_INODE_DELONDISK;
                        if (redirty)
                                ip->sync_flags |= HAMMER_INODE_DDIRTY;

                        /*
                         * Root volume count of inodes
                         */
                        hammer_sync_lock_sh(trans);
                        if ((ip->flags & HAMMER_INODE_ONDISK) == 0) {
                                hammer_modify_volume_field(trans,
                                                           trans->rootvol,
                                                           vol0_stat_inodes);
                                ++ip->hmp->rootvol->ondisk->vol0_stat_inodes;
                                hammer_modify_volume_done(trans->rootvol);
                                ip->flags |= HAMMER_INODE_ONDISK;
                                if (hammer_debug_inode)
                                        kprintf("NOWONDISK %p\n", ip);
                        }
                        hammer_sync_unlock(trans);
                }
        }

        /*
         * If the inode has been destroyed, clean out any left-over flags
         * that may have been set by the frontend.
         */
        if (error == 0 && (ip->flags & HAMMER_INODE_DELETED)) { 
                ip->sync_flags &= ~(HAMMER_INODE_DDIRTY |
                                    HAMMER_INODE_SDIRTY |
                                    HAMMER_INODE_ATIME |
                                    HAMMER_INODE_MTIME);
        }
        return(error);
}

/*
 * Update only the itimes fields.
 *
 * ATIME can be updated without generating any UNDO.  MTIME is updated
 * with UNDO so it is guaranteed to be synchronized properly in case of
 * a crash.
 *
 * Neither field is included in the B-Tree leaf element's CRC, which is how
 * we can get away with updating ATIME the way we do.
 */
static int
hammer_update_itimes(hammer_cursor_t cursor, hammer_inode_t ip)
{
        hammer_transaction_t trans = cursor->trans;
        int error;

retry:
        if ((ip->flags & (HAMMER_INODE_ONDISK|HAMMER_INODE_DELONDISK)) !=
            HAMMER_INODE_ONDISK) {
                return(0);
        }

        hammer_normalize_cursor(cursor);
        cursor->key_beg.localization = ip->obj_localization + 
                                       HAMMER_LOCALIZE_INODE;
        cursor->key_beg.obj_id = ip->obj_id;
        cursor->key_beg.key = 0;
        cursor->key_beg.create_tid = 0;
        cursor->key_beg.delete_tid = 0;
        cursor->key_beg.rec_type = HAMMER_RECTYPE_INODE;
        cursor->key_beg.obj_type = 0;
        cursor->asof = ip->obj_asof;
        cursor->flags &= ~HAMMER_CURSOR_INITMASK;
        cursor->flags |= HAMMER_CURSOR_ASOF;
        cursor->flags |= HAMMER_CURSOR_GET_LEAF;
        cursor->flags |= HAMMER_CURSOR_GET_DATA;
        cursor->flags |= HAMMER_CURSOR_BACKEND;

        error = hammer_btree_lookup(cursor);
        if (error == 0) {
                hammer_cache_node(&ip->cache[0], cursor->node);
                if (ip->sync_flags & HAMMER_INODE_MTIME) {
                        /*
                         * Updating MTIME requires an UNDO.  Just cover
                         * both atime and mtime.
                         */
                        hammer_sync_lock_sh(trans);
                        hammer_modify_buffer(trans, cursor->data_buffer,
                                     HAMMER_ITIMES_BASE(&cursor->data->inode),
                                     HAMMER_ITIMES_BYTES);
                        cursor->data->inode.atime = ip->sync_ino_data.atime;
                        cursor->data->inode.mtime = ip->sync_ino_data.mtime;
                        hammer_modify_buffer_done(cursor->data_buffer);
                        hammer_sync_unlock(trans);
                } else if (ip->sync_flags & HAMMER_INODE_ATIME) {
                        /*
                         * Updating atime only can be done in-place with
                         * no UNDO.
                         */
                        hammer_sync_lock_sh(trans);
                        hammer_modify_buffer(trans, cursor->data_buffer,
                                             NULL, 0);
                        cursor->data->inode.atime = ip->sync_ino_data.atime;
                        hammer_modify_buffer_done(cursor->data_buffer);
                        hammer_sync_unlock(trans);
                }
                ip->sync_flags &= ~(HAMMER_INODE_ATIME | HAMMER_INODE_MTIME);
        }
        if (error == EDEADLK) {
                hammer_done_cursor(cursor);
                error = hammer_init_cursor(trans, cursor,
                                           &ip->cache[0], ip);
                if (error == 0)
                        goto retry;
        }
        return(error);
}

/*
 * Release a reference on an inode, flush as requested.
 *
 * On the last reference we queue the inode to the flusher for its final
 * disposition.
 */
void
hammer_rel_inode(struct hammer_inode *ip, int flush)
{
        /*hammer_mount_t hmp = ip->hmp;*/

        /*
         * Handle disposition when dropping the last ref.
         */
        for (;;) {
                if (hammer_oneref(&ip->lock)) {
                        /*
                         * Determine whether on-disk action is needed for
                         * the inode's final disposition.
                         */
                        KKASSERT(ip->vp == NULL);
                        hammer_inode_unloadable_check(ip, 0);
                        if (ip->flags & HAMMER_INODE_MODMASK) {
                                hammer_flush_inode(ip, 0);
                        } else if (hammer_oneref(&ip->lock)) {
                                hammer_unload_inode(ip);
                                break;
                        }
                } else {
                        if (flush)
                                hammer_flush_inode(ip, 0);

                        /*
                         * The inode still has multiple refs, try to drop
                         * one ref.
                         */
                        KKASSERT(hammer_isactive(&ip->lock) >= 1);
                        if (hammer_isactive(&ip->lock) > 1) {
                                hammer_rel(&ip->lock);
                                break;
                        }
                }
        }
}

/*
 * Unload and destroy the specified inode.  Must be called with one remaining
 * reference.  The reference is disposed of.
 *
 * The inode must be completely clean.
 */
static int
hammer_unload_inode(struct hammer_inode *ip)
{
        hammer_mount_t hmp = ip->hmp;

        KASSERT(hammer_oneref(&ip->lock),
                ("hammer_unload_inode: %d refs", hammer_isactive(&ip->lock)));
        KKASSERT(ip->vp == NULL);
        KKASSERT(ip->flush_state == HAMMER_FST_IDLE);
        KKASSERT(ip->cursor_ip_refs == 0);
        KKASSERT(hammer_notlocked(&ip->lock));
        KKASSERT((ip->flags & HAMMER_INODE_MODMASK) == 0);

        KKASSERT(RB_EMPTY(&ip->rec_tree));
        KKASSERT(TAILQ_EMPTY(&ip->target_list));

        if (ip->flags & HAMMER_INODE_RDIRTY) {
                RB_REMOVE(hammer_redo_rb_tree, &hmp->rb_redo_root, ip);
                ip->flags &= ~HAMMER_INODE_RDIRTY;
        }
        RB_REMOVE(hammer_ino_rb_tree, &hmp->rb_inos_root, ip);

        hammer_free_inode(ip);
        return(0);
}

/*
 * Called during unmounting if a critical error occured.  The in-memory
 * inode and all related structures are destroyed.
 *
 * If a critical error did not occur the unmount code calls the standard
 * release and asserts that the inode is gone.
 */
int
hammer_destroy_inode_callback(struct hammer_inode *ip, void *data __unused)
{
        hammer_record_t rec;

        /*
         * Get rid of the inodes in-memory records, regardless of their
         * state, and clear the mod-mask.
         */
        while ((rec = TAILQ_FIRST(&ip->target_list)) != NULL) {
                TAILQ_REMOVE(&ip->target_list, rec, target_entry);
                rec->target_ip = NULL;
                if (rec->flush_state == HAMMER_FST_SETUP)
                        rec->flush_state = HAMMER_FST_IDLE;
        }
        while ((rec = RB_ROOT(&ip->rec_tree)) != NULL) {
                if (rec->flush_state == HAMMER_FST_FLUSH)
                        --rec->flush_group->refs;
                else
                        hammer_ref(&rec->lock);
                KKASSERT(hammer_oneref(&rec->lock));
                rec->flush_state = HAMMER_FST_IDLE;
                rec->flush_group = NULL;
                rec->flags |= HAMMER_RECF_DELETED_FE; /* wave hands */
                rec->flags |= HAMMER_RECF_DELETED_BE; /* wave hands */
                ++ip->rec_generation;
                hammer_rel_mem_record(rec);
        }
        ip->flags &= ~HAMMER_INODE_MODMASK;
        ip->sync_flags &= ~HAMMER_INODE_MODMASK;
        KKASSERT(ip->vp == NULL);

        /*
         * Remove the inode from any flush group, force it idle.  FLUSH
         * and SETUP states have an inode ref.
         */
        switch(ip->flush_state) {
        case HAMMER_FST_FLUSH:
                RB_REMOVE(hammer_fls_rb_tree, &ip->flush_group->flush_tree, ip);
                --ip->flush_group->refs;
                ip->flush_group = NULL;
                /* fall through */
        case HAMMER_FST_SETUP:
                hammer_rel(&ip->lock);
                ip->flush_state = HAMMER_FST_IDLE;
                /* fall through */
        case HAMMER_FST_IDLE:
                break;
        }

        /*
         * There shouldn't be any associated vnode.  The unload needs at
         * least one ref, if we do have a vp steal its ip ref.
         */
        if (ip->vp) {
                kprintf("hammer_destroy_inode_callback: Unexpected "
                        "vnode association ip %p vp %p\n", ip, ip->vp);
                ip->vp->v_data = NULL;
                ip->vp = NULL;
        } else {
                hammer_ref(&ip->lock);
        }
        hammer_unload_inode(ip);
        return(0);
}

/*
 * Called on mount -u when switching from RW to RO or vise-versa.  Adjust
 * the read-only flag for cached inodes.
 *
 * This routine is called from a RB_SCAN().
 */
int
hammer_reload_inode(hammer_inode_t ip, void *arg __unused)
{
        hammer_mount_t hmp = ip->hmp;

        if (hmp->ronly || hmp->asof != HAMMER_MAX_TID)
                ip->flags |= HAMMER_INODE_RO;
        else
                ip->flags &= ~HAMMER_INODE_RO;
        return(0);
}

/*
 * A transaction has modified an inode, requiring updates as specified by
 * the passed flags.
 *
 * HAMMER_INODE_DDIRTY: Inode data has been updated, not incl mtime/atime,
 *                      and not including size changes due to write-append
 *                      (but other size changes are included).
 * HAMMER_INODE_SDIRTY: Inode data has been updated, size changes due to
 *                      write-append.
 * HAMMER_INODE_XDIRTY: Dirty in-memory records
 * HAMMER_INODE_BUFS:   Dirty buffer cache buffers
 * HAMMER_INODE_DELETED: Inode record/data must be deleted
 * HAMMER_INODE_ATIME/MTIME: mtime/atime has been updated
 */
void
hammer_modify_inode(hammer_transaction_t trans, hammer_inode_t ip, int flags)
{
        /* 
         * ronly of 0 or 2 does not trigger assertion.
         * 2 is a special error state 
         */
        KKASSERT(ip->hmp->ronly != 1 ||
                  (flags & (HAMMER_INODE_DDIRTY | HAMMER_INODE_XDIRTY | 
                            HAMMER_INODE_SDIRTY |
                            HAMMER_INODE_BUFS | HAMMER_INODE_DELETED |
                            HAMMER_INODE_ATIME | HAMMER_INODE_MTIME)) == 0);
        if ((ip->flags & HAMMER_INODE_RSV_INODES) == 0) {
                ip->flags |= HAMMER_INODE_RSV_INODES;
                ++ip->hmp->rsv_inodes;
        }

        /*
         * Set the NEWINODE flag in the transaction if the inode
         * transitions to a dirty state.  This is used to track
         * the load on the inode cache.
         */
        if (trans &&
            (ip->flags & HAMMER_INODE_MODMASK) == 0 &&
            (flags & HAMMER_INODE_MODMASK)) {
                trans->flags |= HAMMER_TRANSF_NEWINODE;
        }
        if (flags & HAMMER_INODE_MODMASK)
                hammer_inode_dirty(ip);
        ip->flags |= flags;
}

/*
 * Attempt to quickly update the atime for a hammer inode.  Return 0 on
 * success, -1 on failure.
 *
 * We attempt to update the atime with only the ip lock and not the
 * whole filesystem lock in order to improve concurrency.  We can only
 * do this safely if the ATIME flag is already pending on the inode.
 *
 * This function is called via a vnops path (ip pointer is stable) without
 * fs_token held.
 */
int
hammer_update_atime_quick(hammer_inode_t ip)
{
        struct timeval tv;
        int res = -1;

        if ((ip->flags & HAMMER_INODE_RO) ||
            (ip->hmp->mp->mnt_flag & MNT_NOATIME)) {
                /*
                 * Silently indicate success on read-only mount/snap
                 */
                res = 0;
        } else if (ip->flags & HAMMER_INODE_ATIME) {
                /*
                 * Double check with inode lock held against backend.  This
                 * is only safe if all we need to do is update
                 * ino_data.atime.
                 */
                getmicrotime(&tv);
                hammer_lock_ex(&ip->lock);
                if (ip->flags & HAMMER_INODE_ATIME) {
                        ip->ino_data.atime =
                            (unsigned long)tv.tv_sec * 1000000ULL + tv.tv_usec;
                        res = 0;
                }
                hammer_unlock(&ip->lock);
        }
        return res;
}

/*
 * Request that an inode be flushed.  This whole mess cannot block and may
 * recurse (if not synchronous).  Once requested HAMMER will attempt to
 * actively flush the inode until the flush can be done.
 *
 * The inode may already be flushing, or may be in a setup state.  We can
 * place the inode in a flushing state if it is currently idle and flag it
 * to reflush if it is currently flushing.
 *
 * Upon return if the inode could not be flushed due to a setup
 * dependancy, then it will be automatically flushed when the dependancy
 * is satisfied.
 */
void
hammer_flush_inode(hammer_inode_t ip, int flags)
{
        hammer_mount_t hmp;
        hammer_flush_group_t flg;
        int good;

        /*
         * fill_flush_group is the first flush group we may be able to
         * continue filling, it may be open or closed but it will always
         * be past the currently flushing (running) flg.
         *
         * next_flush_group is the next open flush group.
         */
        hmp = ip->hmp;
        while ((flg = hmp->fill_flush_group) != NULL) {
                KKASSERT(flg->running == 0);
                if (flg->total_count + flg->refs <= ip->hmp->undo_rec_limit &&
                    flg->total_count <= hammer_autoflush) {
                        break;
                }
                hmp->fill_flush_group = TAILQ_NEXT(flg, flush_entry);
                hammer_flusher_async(ip->hmp, flg);
        }
        if (flg == NULL) {
                flg = kmalloc(sizeof(*flg), hmp->m_misc, M_WAITOK|M_ZERO);
                flg->seq = hmp->flusher.next++;
                if (hmp->next_flush_group == NULL)
                        hmp->next_flush_group = flg;
                if (hmp->fill_flush_group == NULL)
                        hmp->fill_flush_group = flg;
                RB_INIT(&flg->flush_tree);
                TAILQ_INSERT_TAIL(&hmp->flush_group_list, flg, flush_entry);
        }

        /*
         * Trivial 'nothing to flush' case.  If the inode is in a SETUP
         * state we have to put it back into an IDLE state so we can
         * drop the extra ref.
         *
         * If we have a parent dependancy we must still fall through
         * so we can run it.
         */
        if ((ip->flags & HAMMER_INODE_MODMASK) == 0) {
                if (ip->flush_state == HAMMER_FST_SETUP &&
                    TAILQ_EMPTY(&ip->target_list)) {
                        ip->flush_state = HAMMER_FST_IDLE;
                        hammer_rel_inode(ip, 0);
                }
                if (ip->flush_state == HAMMER_FST_IDLE)
                        return;
        }

        /*
         * Our flush action will depend on the current state.
         */
        switch(ip->flush_state) {
        case HAMMER_FST_IDLE:
                /*
                 * We have no dependancies and can flush immediately.  Some
                 * our children may not be flushable so we have to re-test
                 * with that additional knowledge.
                 */
                hammer_flush_inode_core(ip, flg, flags);
                break;
        case HAMMER_FST_SETUP:
                /*
                 * Recurse upwards through dependancies via target_list
                 * and start their flusher actions going if possible.
                 *
                 * 'good' is our connectivity.  -1 means we have none and
                 * can't flush, 0 means there weren't any dependancies, and
                 * 1 means we have good connectivity.
                 */
                good = hammer_setup_parent_inodes(ip, 0, flg);

                if (good >= 0) {
                        /*
                         * We can continue if good >= 0.  Determine how 
                         * many records under our inode can be flushed (and
                         * mark them).
                         */
                        hammer_flush_inode_core(ip, flg, flags);
                } else {
                        /*
                         * Parent has no connectivity, tell it to flush
                         * us as soon as it does.
                         *
                         * The REFLUSH flag is also needed to trigger
                         * dependancy wakeups.
                         */
                        ip->flags |= HAMMER_INODE_CONN_DOWN |
                                     HAMMER_INODE_REFLUSH;
                        if (flags & HAMMER_FLUSH_SIGNAL) {
                                ip->flags |= HAMMER_INODE_RESIGNAL;
                                hammer_flusher_async(ip->hmp, flg);
                        }
                }
                break;
        case HAMMER_FST_FLUSH:
                /*
                 * We are already flushing, flag the inode to reflush
                 * if needed after it completes its current flush.
                 *
                 * The REFLUSH flag is also needed to trigger
                 * dependancy wakeups.
                 */
                if ((ip->flags & HAMMER_INODE_REFLUSH) == 0)
                        ip->flags |= HAMMER_INODE_REFLUSH;
                if (flags & HAMMER_FLUSH_SIGNAL) {
                        ip->flags |= HAMMER_INODE_RESIGNAL;
                        hammer_flusher_async(ip->hmp, flg);
                }
                break;
        }
}

/*
 * Scan ip->target_list, which is a list of records owned by PARENTS to our
 * ip which reference our ip.
 *
 * XXX This is a huge mess of recursive code, but not one bit of it blocks
 *     so for now do not ref/deref the structures.  Note that if we use the
 *     ref/rel code later, the rel CAN block.
 */
static int
hammer_setup_parent_inodes(hammer_inode_t ip, int depth,
                           hammer_flush_group_t flg)
{
        hammer_record_t depend;
        int good;
        int r;

        /*
         * If we hit our recursion limit and we have parent dependencies
         * We cannot continue.  Returning < 0 will cause us to be flagged
         * for reflush.  Returning -2 cuts off additional dependency checks
         * because they are likely to also hit the depth limit.
         *
         * We cannot return < 0 if there are no dependencies or there might
         * not be anything to wakeup (ip).
         */
        if (depth == 20 && TAILQ_FIRST(&ip->target_list)) {
                if (hammer_debug_general & 0x10000)
                        krateprintf(&hammer_gen_krate,
                            "HAMMER Warning: depth limit reached on "
                            "setup recursion, inode %p %016llx\n",
                            ip, (long long)ip->obj_id);
                return(-2);
        }

        /*
         * Scan dependencies
         */
        good = 0;
        TAILQ_FOREACH(depend, &ip->target_list, target_entry) {
                r = hammer_setup_parent_inodes_helper(depend, depth, flg);
                KKASSERT(depend->target_ip == ip);
                if (r < 0 && good == 0)
                        good = -1;
                if (r > 0)
                        good = 1;

                /*
                 * If we failed due to the recursion depth limit then stop
                 * now.
                 */
                if (r == -2)
                        break;
        }
        return(good);
}

/*
 * This helper function takes a record representing the dependancy between
 * the parent inode and child inode.
 *
 * record->ip           = parent inode
 * record->target_ip    = child inode
 * 
 * We are asked to recurse upwards and convert the record from SETUP
 * to FLUSH if possible.
 *
 * Return 1 if the record gives us connectivity
 *
 * Return 0 if the record is not relevant 
 *
 * Return -1 if we can't resolve the dependancy and there is no connectivity.
 */
static int
hammer_setup_parent_inodes_helper(hammer_record_t record, int depth,
                                  hammer_flush_group_t flg)
{
        hammer_inode_t pip;
        int good;

        KKASSERT(record->flush_state != HAMMER_FST_IDLE);
        pip = record->ip;

        /*
         * If the record is already flushing, is it in our flush group?
         *
         * If it is in our flush group but it is a general record or a 
         * delete-on-disk, it does not improve our connectivity (return 0),
         * and if the target inode is not trying to destroy itself we can't
         * allow the operation yet anyway (the second return -1).
         */
        if (record->flush_state == HAMMER_FST_FLUSH) {
                /*
                 * If not in our flush group ask the parent to reflush
                 * us as soon as possible.
                 */
                if (record->flush_group != flg) {
                        pip->flags |= HAMMER_INODE_REFLUSH;
                        record->target_ip->flags |= HAMMER_INODE_CONN_DOWN;
                        return(-1);
                }

                /*
                 * If in our flush group everything is already set up,
                 * just return whether the record will improve our
                 * visibility or not.
                 */
                if (record->type == HAMMER_MEM_RECORD_ADD)
                        return(1);
                return(0);
        }

        /*
         * It must be a setup record.  Try to resolve the setup dependancies
         * by recursing upwards so we can place ip on the flush list.
         *
         * Limit ourselves to 20 levels of recursion to avoid blowing out
         * the kernel stack.  If we hit the recursion limit we can't flush
         * until the parent flushes.  The parent will flush independantly
         * on its own and ultimately a deep recursion will be resolved.
         */
        KKASSERT(record->flush_state == HAMMER_FST_SETUP);

        good = hammer_setup_parent_inodes(pip, depth + 1, flg);

        /*
         * If good < 0 the parent has no connectivity and we cannot safely
         * flush the directory entry, which also means we can't flush our
         * ip.  Flag us for downward recursion once the parent's
         * connectivity is resolved.  Flag the parent for [re]flush or it
         * may not check for downward recursions.
         */
        if (good < 0) {
                pip->flags |= HAMMER_INODE_REFLUSH;
                record->target_ip->flags |= HAMMER_INODE_CONN_DOWN;
                return(good);
        }

        /*
         * We are go, place the parent inode in a flushing state so we can
         * place its record in a flushing state.  Note that the parent
         * may already be flushing.  The record must be in the same flush
         * group as the parent.
         */
        if (pip->flush_state != HAMMER_FST_FLUSH)
                hammer_flush_inode_core(pip, flg, HAMMER_FLUSH_RECURSION);
        KKASSERT(pip->flush_state == HAMMER_FST_FLUSH);

        /*
         * It is possible for a rename to create a loop in the recursion
         * and revisit a record.  This will result in the record being
         * placed in a flush state unexpectedly.  This check deals with
         * the case.
         */
        if (record->flush_state == HAMMER_FST_FLUSH) {
                if (record->type == HAMMER_MEM_RECORD_ADD)
                        return(1);
                return(0);
        }

        KKASSERT(record->flush_state == HAMMER_FST_SETUP);

#if 0
        if (record->type == HAMMER_MEM_RECORD_DEL &&
            (record->target_ip->flags & (HAMMER_INODE_DELETED|HAMMER_INODE_DELONDISK)) == 0) {
                /*
                 * Regardless of flushing state we cannot sync this path if the
                 * record represents a delete-on-disk but the target inode
                 * is not ready to sync its own deletion.
                 *
                 * XXX need to count effective nlinks to determine whether
                 * the flush is ok, otherwise removing a hardlink will
                 * just leave the DEL record to rot.
                 */
                record->target_ip->flags |= HAMMER_INODE_REFLUSH;
                return(-1);
        } else
#endif
        if (pip->flush_group == flg) {
                /*
                 * Because we have not calculated nlinks yet we can just
                 * set records to the flush state if the parent is in
                 * the same flush group as we are.
                 */
                record->flush_state = HAMMER_FST_FLUSH;
                record->flush_group = flg;
                ++record->flush_group->refs;
                hammer_ref(&record->lock);

                /*
                 * A general directory-add contributes to our visibility.
                 *
                 * Otherwise it is probably a directory-delete or 
                 * delete-on-disk record and does not contribute to our
                 * visbility (but we can still flush it).
                 */
                if (record->type == HAMMER_MEM_RECORD_ADD)
                        return(1);
                return(0);
        } else {
                /*
                 * If the parent is not in our flush group we cannot
                 * flush this record yet, there is no visibility.
                 * We tell the parent to reflush and mark ourselves
                 * so the parent knows it should flush us too.
                 */
                pip->flags |= HAMMER_INODE_REFLUSH;
                record->target_ip->flags |= HAMMER_INODE_CONN_DOWN;
                return(-1);
        }
}

/*
 * This is the core routine placing an inode into the FST_FLUSH state.
 */
static void
hammer_flush_inode_core(hammer_inode_t ip, hammer_flush_group_t flg, int flags)
{
        hammer_mount_t hmp = ip->hmp;
        int go_count;

        /*
         * Set flush state and prevent the flusher from cycling into
         * the next flush group.  Do not place the ip on the list yet.
         * Inodes not in the idle state get an extra reference.
         */
        KKASSERT(ip->flush_state != HAMMER_FST_FLUSH);
        if (ip->flush_state == HAMMER_FST_IDLE)
                hammer_ref(&ip->lock);
        ip->flush_state = HAMMER_FST_FLUSH;
        ip->flush_group = flg;
        ++hmp->flusher.group_lock;
        ++hmp->count_iqueued;
        ++hammer_count_iqueued;
        ++flg->total_count;
        hammer_redo_fifo_start_flush(ip);

#if 0
        /*
         * We need to be able to vfsync/truncate from the backend.
         *
         * XXX Any truncation from the backend will acquire the vnode
         *     independently.
         */
        KKASSERT((ip->flags & HAMMER_INODE_VHELD) == 0);
        if (ip->vp && (ip->vp->v_flag & VINACTIVE) == 0) {
                ip->flags |= HAMMER_INODE_VHELD;
                vref(ip->vp);
        }
#endif

        /*
         * Figure out how many in-memory records we can actually flush
         * (not including inode meta-data, buffers, etc).
         */
        KKASSERT((ip->flags & HAMMER_INODE_WOULDBLOCK) == 0);
        if (flags & HAMMER_FLUSH_RECURSION) {
                /*
                 * If this is a upwards recursion we do not want to
                 * recurse down again!
                 */
                go_count = 1;
#if 0
        } else if (ip->flags & HAMMER_INODE_WOULDBLOCK) {
                /*
                 * No new records are added if we must complete a flush
                 * from a previous cycle, but we do have to move the records
                 * from the previous cycle to the current one.
                 */
#if 0
                go_count = RB_SCAN(hammer_rec_rb_tree, &ip->rec_tree, NULL,
                                   hammer_syncgrp_child_callback, NULL);
#endif
                go_count = 1;
#endif
        } else {
                /*
                 * Normal flush, scan records and bring them into the flush.
                 * Directory adds and deletes are usually skipped (they are
                 * grouped with the related inode rather then with the
                 * directory).
                 *
                 * go_count can be negative, which means the scan aborted
                 * due to the flush group being over-full and we should
                 * flush what we have.
                 */
                go_count = RB_SCAN(hammer_rec_rb_tree, &ip->rec_tree, NULL,
                                   hammer_setup_child_callback, NULL);
        }

        /*
         * This is a more involved test that includes go_count.  If we
         * can't flush, flag the inode and return.  If go_count is 0 we
         * were are unable to flush any records in our rec_tree and
         * must ignore the XDIRTY flag.
         */
        if (go_count == 0) {
                if ((ip->flags & HAMMER_INODE_MODMASK_NOXDIRTY) == 0) {
                        --hmp->count_iqueued;
                        --hammer_count_iqueued;

                        --flg->total_count;
                        ip->flush_state = HAMMER_FST_SETUP;
                        ip->flush_group = NULL;
                        if (flags & HAMMER_FLUSH_SIGNAL) {
                                ip->flags |= HAMMER_INODE_REFLUSH |
                                             HAMMER_INODE_RESIGNAL;
                        } else {
                                ip->flags |= HAMMER_INODE_REFLUSH;
                        }
#if 0
                        if (ip->flags & HAMMER_INODE_VHELD) {
                                ip->flags &= ~HAMMER_INODE_VHELD;
                                vrele(ip->vp);
                        }
#endif

                        /*
                         * REFLUSH is needed to trigger dependancy wakeups
                         * when an inode is in SETUP.
                         */
                        ip->flags |= HAMMER_INODE_REFLUSH;
                        if (--hmp->flusher.group_lock == 0)
                                wakeup(&hmp->flusher.group_lock);
                        return;
                }
        }

        /*
         * Snapshot the state of the inode for the backend flusher.
         *
         * We continue to retain save_trunc_off even when all truncations
         * have been resolved as an optimization to determine if we can
         * skip the B-Tree lookup for overwrite deletions.
         *
         * NOTE: The DELETING flag is a mod flag, but it is also sticky,
         * and stays in ip->flags.  Once set, it stays set until the
         * inode is destroyed.
         */
        if (ip->flags & HAMMER_INODE_TRUNCATED) {
                KKASSERT((ip->sync_flags & HAMMER_INODE_TRUNCATED) == 0);
                ip->sync_trunc_off = ip->trunc_off;
                ip->trunc_off = 0x7FFFFFFFFFFFFFFFLL;
                ip->flags &= ~HAMMER_INODE_TRUNCATED;
                ip->sync_flags |= HAMMER_INODE_TRUNCATED;

                /*
                 * The save_trunc_off used to cache whether the B-Tree
                 * holds any records past that point is not used until
                 * after the truncation has succeeded, so we can safely
                 * set it now.
                 */
                if (ip->save_trunc_off > ip->sync_trunc_off)
                        ip->save_trunc_off = ip->sync_trunc_off;
        }
        ip->sync_flags |= (ip->flags & HAMMER_INODE_MODMASK &
                           ~HAMMER_INODE_TRUNCATED);
        ip->sync_ino_leaf = ip->ino_leaf;
        ip->sync_ino_data = ip->ino_data;
        ip->flags &= ~HAMMER_INODE_MODMASK | HAMMER_INODE_TRUNCATED;
#ifdef DEBUG_TRUNCATE
        if ((ip->sync_flags & HAMMER_INODE_TRUNCATED) && ip == HammerTruncIp)
                kprintf("truncateS %016llx\n", ip->sync_trunc_off);
#endif

        /*
         * The flusher list inherits our inode and reference.
         */
        KKASSERT(flg->running == 0);
        RB_INSERT(hammer_fls_rb_tree, &flg->flush_tree, ip);
        if (--hmp->flusher.group_lock == 0)
                wakeup(&hmp->flusher.group_lock);

        /*
         * Auto-flush the group if it grows too large.  Make sure the
         * inode reclaim wait pipeline continues to work.
         */
        if (flg->total_count >= hammer_autoflush ||
            flg->total_count >= hammer_limit_reclaims / 4) {
                if (hmp->fill_flush_group == flg)
                        hmp->fill_flush_group = TAILQ_NEXT(flg, flush_entry);
                hammer_flusher_async(hmp, flg);
        }
}

/*
 * Callback for scan of ip->rec_tree.  Try to include each record in our
 * flush.  ip->flush_group has been set but the inode has not yet been
 * moved into a flushing state.
 *
 * If we get stuck on a record we have to set HAMMER_INODE_REFLUSH on
 * both inodes.
 *
 * We return 1 for any record placed or found in FST_FLUSH, which prevents
 * the caller from shortcutting the flush.
 */
static int
hammer_setup_child_callback(hammer_record_t rec, void *data)
{
        hammer_flush_group_t flg;
        hammer_inode_t target_ip;
        hammer_inode_t ip;
        int r;

        /*
         * Records deleted or committed by the backend are ignored.
         * Note that the flush detects deleted frontend records at
         * multiple points to deal with races.  This is just the first
         * line of defense.  The only time HAMMER_RECF_DELETED_FE cannot
         * be set is when HAMMER_RECF_INTERLOCK_BE is set, because it
         * messes up link-count calculations.
         *
         * NOTE: Don't get confused between record deletion and, say,
         * directory entry deletion.  The deletion of a directory entry
         * which is on-media has nothing to do with the record deletion
         * flags.
         */
        if (rec->flags & (HAMMER_RECF_DELETED_FE | HAMMER_RECF_DELETED_BE |
                          HAMMER_RECF_COMMITTED)) {
                if (rec->flush_state == HAMMER_FST_FLUSH) {
                        KKASSERT(rec->flush_group == rec->ip->flush_group);
                        r = 1;
                } else {
                        r = 0;
                }
                return(r);
        }

        /*
         * If the record is in an idle state it has no dependancies and
         * can be flushed.
         */
        ip = rec->ip;
        flg = ip->flush_group;
        r = 0;

        switch(rec->flush_state) {
        case HAMMER_FST_IDLE:
                /*
                 * The record has no setup dependancy, we can flush it.
                 */
                KKASSERT(rec->target_ip == NULL);
                rec->flush_state = HAMMER_FST_FLUSH;
                rec->flush_group = flg;
                ++flg->refs;
                hammer_ref(&rec->lock);
                r = 1;
                break;
        case HAMMER_FST_SETUP:
                /*
                 * The record has a setup dependancy.  These are typically
                 * directory entry adds and deletes.  Such entries will be
                 * flushed when their inodes are flushed so we do not
                 * usually have to add them to the flush here.  However,
                 * if the target_ip has set HAMMER_INODE_CONN_DOWN then
                 * it is asking us to flush this record (and it).
                 */
                target_ip = rec->target_ip;
                KKASSERT(target_ip != NULL);
                KKASSERT(target_ip->flush_state != HAMMER_FST_IDLE);

                /*
                 * If the target IP is already flushing in our group
                 * we could associate the record, but target_ip has
                 * already synced ino_data to sync_ino_data and we
                 * would also have to adjust nlinks.   Plus there are
                 * ordering issues for adds and deletes.
                 *
                 * Reflush downward if this is an ADD, and upward if
                 * this is a DEL.
                 */
                if (target_ip->flush_state == HAMMER_FST_FLUSH) {
                        if (rec->type == HAMMER_MEM_RECORD_ADD)
                                ip->flags |= HAMMER_INODE_REFLUSH;
                        else
                                target_ip->flags |= HAMMER_INODE_REFLUSH;
                        break;
                } 

                /*
                 * Target IP is not yet flushing.  This can get complex
                 * because we have to be careful about the recursion.
                 *
                 * Directories create an issue for us in that if a flush
                 * of a directory is requested the expectation is to flush
                 * any pending directory entries, but this will cause the
                 * related inodes to recursively flush as well.  We can't
                 * really defer the operation so just get as many as we
                 * can and
                 */
#if 0
                if ((target_ip->flags & HAMMER_INODE_RECLAIM) == 0 &&
                    (target_ip->flags & HAMMER_INODE_CONN_DOWN) == 0) {
                        /*
                         * We aren't reclaiming and the target ip was not
                         * previously prevented from flushing due to this
                         * record dependancy.  Do not flush this record.
                         */
                        /*r = 0;*/
                } else
#endif
                if (flg->total_count + flg->refs >
                           ip->hmp->undo_rec_limit) {
                        /*
                         * Our flush group is over-full and we risk blowing
                         * out the UNDO FIFO.  Stop the scan, flush what we
                         * have, then reflush the directory.
                         *
                         * The directory may be forced through multiple
                         * flush groups before it can be completely
                         * flushed.
                         */
                        ip->flags |= HAMMER_INODE_RESIGNAL |
                                     HAMMER_INODE_REFLUSH;
                        r = -1;
                } else if (rec->type == HAMMER_MEM_RECORD_ADD) {
                        /*
                         * If the target IP is not flushing we can force
                         * it to flush, even if it is unable to write out
                         * any of its own records we have at least one in
                         * hand that we CAN deal with.
                         */
                        rec->flush_state = HAMMER_FST_FLUSH;
                        rec->flush_group = flg;
                        ++flg->refs;
                        hammer_ref(&rec->lock);
                        hammer_flush_inode_core(target_ip, flg,
                                                HAMMER_FLUSH_RECURSION);
                        r = 1;
                } else {
                        /*
                         * General or delete-on-disk record.
                         *
                         * XXX this needs help.  If a delete-on-disk we could
                         * disconnect the target.  If the target has its own
                         * dependancies they really need to be flushed.
                         *
                         * XXX
                         */
                        rec->flush_state = HAMMER_FST_FLUSH;
                        rec->flush_group = flg;
                        ++flg->refs;
                        hammer_ref(&rec->lock);
                        hammer_flush_inode_core(target_ip, flg,
                                                HAMMER_FLUSH_RECURSION);
                        r = 1;
                }
                break;
        case HAMMER_FST_FLUSH:
                /* 
                 * The record could be part of a previous flush group if the
                 * inode is a directory (the record being a directory entry).
                 * Once the flush group was closed a hammer_test_inode()
                 * function can cause a new flush group to be setup, placing
                 * the directory inode itself in a new flush group.
                 *
                 * When associated with a previous flush group we count it
                 * as if it were in our current flush group, since it will
                 * effectively be flushed by the time we flush our current
                 * flush group.
                 */
                KKASSERT(
                    rec->ip->ino_data.obj_type == HAMMER_OBJTYPE_DIRECTORY ||
                    rec->flush_group == flg);
                r = 1;
                break;
        }
        return(r);
}

#if 0
/*
 * This version just moves records already in a flush state to the new
 * flush group and that is it.
 */
static int
hammer_syncgrp_child_callback(hammer_record_t rec, void *data)
{
        hammer_inode_t ip = rec->ip;

        switch(rec->flush_state) {
        case HAMMER_FST_FLUSH:
                KKASSERT(rec->flush_group == ip->flush_group);
                break;
        default:
                break;
        }
        return(0);
}
#endif

/*
 * Wait for a previously queued flush to complete.
 *
 * If a critical error occured we don't try to wait.
 */
void
hammer_wait_inode(hammer_inode_t ip)
{
        /*
         * The inode can be in a SETUP state in which case RESIGNAL
         * should be set.  If RESIGNAL is not set then the previous
         * flush completed and a later operation placed the inode
         * in a passive setup state again, so we're done.
         *
         * The inode can be in a FLUSH state in which case we
         * can just wait for completion.
         */
        while (ip->flush_state == HAMMER_FST_FLUSH ||
            (ip->flush_state == HAMMER_FST_SETUP &&
             (ip->flags & HAMMER_INODE_RESIGNAL))) {
                /*
                 * Don't try to flush on a critical error
                 */
                if (ip->hmp->flags & HAMMER_MOUNT_CRITICAL_ERROR)
                        break;

                /*
                 * If the inode was already being flushed its flg
                 * may not have been queued to the backend.  We
                 * have to make sure it gets queued or we can wind
                 * up blocked or deadlocked (particularly if we are
                 * the vnlru thread).
                 */
                if (ip->flush_state == HAMMER_FST_FLUSH) {
                        KKASSERT(ip->flush_group);
                        if (ip->flush_group->closed == 0) {
                                if (hammer_debug_inode) {
                                        kprintf("hammer: debug: forcing "
                                                "async flush ip %016jx\n",
                                                (intmax_t)ip->obj_id);
                                }
                                hammer_flusher_async(ip->hmp,
                                                     ip->flush_group);
                                continue; /* retest */
                        }
                }

                /*
                 * In a flush state with the flg queued to the backend
                 * or in a setup state with RESIGNAL set, we can safely
                 * wait.
                 */
                ip->flags |= HAMMER_INODE_FLUSHW;
                tsleep(&ip->flags, 0, "hmrwin", 0);
        }

#if 0
        /*
         * The inode may have been in a passive setup state,
         * call flush to make sure we get signaled.
         */
        if (ip->flush_state == HAMMER_FST_SETUP)
                hammer_flush_inode(ip, HAMMER_FLUSH_SIGNAL);
#endif

}

/*
 * Called by the backend code when a flush has been completed.
 * The inode has already been removed from the flush list.
 *
 * A pipelined flush can occur, in which case we must re-enter the
 * inode on the list and re-copy its fields.
 */
void
hammer_flush_inode_done(hammer_inode_t ip, int error)
{
        hammer_mount_t hmp;
        int dorel;

        KKASSERT(ip->flush_state == HAMMER_FST_FLUSH);

        hmp = ip->hmp;

        /*
         * Auto-reflush if the backend could not completely flush
         * the inode.  This fixes a case where a deferred buffer flush
         * could cause fsync to return early.
         */
        if (ip->sync_flags & HAMMER_INODE_MODMASK)
                ip->flags |= HAMMER_INODE_REFLUSH;

        /*
         * Merge left-over flags back into the frontend and fix the state.
         * Incomplete truncations are retained by the backend.
         */
        ip->error = error;
        ip->flags |= ip->sync_flags & ~HAMMER_INODE_TRUNCATED;
        ip->sync_flags &= HAMMER_INODE_TRUNCATED;

        /*
         * The backend may have adjusted nlinks, so if the adjusted nlinks
         * does not match the fronttend set the frontend's DDIRTY flag again.
         */
        if (ip->ino_data.nlinks != ip->sync_ino_data.nlinks)
                ip->flags |= HAMMER_INODE_DDIRTY;

        /*
         * Fix up the dirty buffer status.
         */
        if (ip->vp && RB_ROOT(&ip->vp->v_rbdirty_tree)) {
                ip->flags |= HAMMER_INODE_BUFS;
        }
        hammer_redo_fifo_end_flush(ip);

        /*
         * Re-set the XDIRTY flag if some of the inode's in-memory records
         * could not be flushed.
         */
        KKASSERT((RB_EMPTY(&ip->rec_tree) &&
                  (ip->flags & HAMMER_INODE_XDIRTY) == 0) ||
                 (!RB_EMPTY(&ip->rec_tree) &&
                  (ip->flags & HAMMER_INODE_XDIRTY) != 0));

        /*
         * Do not lose track of inodes which no longer have vnode
         * assocations, otherwise they may never get flushed again.
         *
         * The reflush flag can be set superfluously, causing extra pain
         * for no reason.  If the inode is no longer modified it no longer
         * needs to be flushed.
         */
        if (ip->flags & HAMMER_INODE_MODMASK) {
                if (ip->vp == NULL)
                        ip->flags |= HAMMER_INODE_REFLUSH;
        } else {
                ip->flags &= ~HAMMER_INODE_REFLUSH;
        }
        if (ip->flags & HAMMER_INODE_MODMASK)
                hammer_inode_dirty(ip);

        /*
         * Adjust the flush state.
         */
        if (ip->flags & HAMMER_INODE_WOULDBLOCK) {
                /*
                 * We were unable to flush out all our records, leave the
                 * inode in a flush state and in the current flush group.
                 * The flush group will be re-run.
                 *
                 * This occurs if the UNDO block gets too full or there is
                 * too much dirty meta-data and allows the flusher to
                 * finalize the UNDO block and then re-flush.
                 */
                ip->flags &= ~HAMMER_INODE_WOULDBLOCK;
                dorel = 0;
        } else {
                /*
                 * Remove from the flush_group
                 */
                RB_REMOVE(hammer_fls_rb_tree, &ip->flush_group->flush_tree, ip);
                ip->flush_group = NULL;

#if 0
                /*
                 * Clean up the vnode ref and tracking counts.
                 */
                if (ip->flags & HAMMER_INODE_VHELD) {
                        ip->flags &= ~HAMMER_INODE_VHELD;
                        vrele(ip->vp);
                }
#endif
                --hmp->count_iqueued;
                --hammer_count_iqueued;

                /*
                 * And adjust the state.
                 */
                if (TAILQ_EMPTY(&ip->target_list) && RB_EMPTY(&ip->rec_tree)) {
                        ip->flush_state = HAMMER_FST_IDLE;
                        dorel = 1;
                } else {
                        ip->flush_state = HAMMER_FST_SETUP;
                        dorel = 0;
                }

                /*
                 * If the frontend is waiting for a flush to complete,
                 * wake it up.
                 */
                if (ip->flags & HAMMER_INODE_FLUSHW) {
                        ip->flags &= ~HAMMER_INODE_FLUSHW;
                        wakeup(&ip->flags);
                }

                /*
                 * If the frontend made more changes and requested another
                 * flush, then try to get it running.
                 *
                 * Reflushes are aborted when the inode is errored out.
                 */
                if (ip->flags & HAMMER_INODE_REFLUSH) {
                        ip->flags &= ~HAMMER_INODE_REFLUSH;
                        if (ip->flags & HAMMER_INODE_RESIGNAL) {
                                ip->flags &= ~HAMMER_INODE_RESIGNAL;
                                hammer_flush_inode(ip, HAMMER_FLUSH_SIGNAL);
                        } else {
                                hammer_flush_inode(ip, 0);
                        }
                }
        }

        /*
         * If we have no parent dependancies we can clear CONN_DOWN
         */
        if (TAILQ_EMPTY(&ip->target_list))
                ip->flags &= ~HAMMER_INODE_CONN_DOWN;

        /*
         * If the inode is now clean drop the space reservation.
         */
        if ((ip->flags & HAMMER_INODE_MODMASK) == 0 &&
            (ip->flags & HAMMER_INODE_RSV_INODES)) {
                ip->flags &= ~HAMMER_INODE_RSV_INODES;
                --hmp->rsv_inodes;
        }

        ip->flags &= ~HAMMER_INODE_SLAVEFLUSH;

        if (dorel)
                hammer_rel_inode(ip, 0);
}

/*
 * Called from hammer_sync_inode() to synchronize in-memory records
 * to the media.
 */
static int
hammer_sync_record_callback(hammer_record_t record, void *data)
{
        hammer_cursor_t cursor = data;
        hammer_transaction_t trans = cursor->trans;
        hammer_mount_t hmp = trans->hmp;
        int error;

        /*
         * Skip records that do not belong to the current flush.
         */
        ++hammer_stats_record_iterations;
        if (record->flush_state != HAMMER_FST_FLUSH)
                return(0);

#if 1
        if (record->flush_group != record->ip->flush_group) {
                kprintf("sync_record %p ip %p bad flush group %p %p\n", record, record->ip, record->flush_group ,record->ip->flush_group);
                if (hammer_debug_critical)
                        Debugger("blah2");
                return(0);
        }
#endif
        KKASSERT(record->flush_group == record->ip->flush_group);

        /*
         * Interlock the record using the BE flag.  Once BE is set the
         * frontend cannot change the state of FE.
         *
         * NOTE: If FE is set prior to us setting BE we still sync the
         * record out, but the flush completion code converts it to 
         * a delete-on-disk record instead of destroying it.
         */
        KKASSERT((record->flags & HAMMER_RECF_INTERLOCK_BE) == 0);
        record->flags |= HAMMER_RECF_INTERLOCK_BE;

        /*
         * The backend has already disposed of the record.
         */
        if (record->flags & (HAMMER_RECF_DELETED_BE | HAMMER_RECF_COMMITTED)) {
                error = 0;
                goto done;
        }

        /*
         * If the whole inode is being deleted and all on-disk records will
         * be deleted very soon, we can't sync any new records to disk
         * because they will be deleted in the same transaction they were
         * created in (delete_tid == create_tid), which will assert.
         *
         * XXX There may be a case with RECORD_ADD with DELETED_FE set
         * that we currently panic on.
         */
        if (record->ip->sync_flags & HAMMER_INODE_DELETING) {
                switch(record->type) {
                case HAMMER_MEM_RECORD_DATA:
                        /*
                         * We don't have to do anything, if the record was
                         * committed the space will have been accounted for
                         * in the blockmap.
                         */
                        /* fall through */
                case HAMMER_MEM_RECORD_GENERAL:
                        /*
                         * Set deleted-by-backend flag.  Do not set the
                         * backend committed flag, because we are throwing
                         * the record away.
                         */
                        record->flags |= HAMMER_RECF_DELETED_BE;
                        ++record->ip->rec_generation;
                        error = 0;
                        goto done;
                case HAMMER_MEM_RECORD_ADD:
                        panic("hammer_sync_record_callback: illegal add "
                              "during inode deletion record %p", record);
                        break; /* NOT REACHED */
                case HAMMER_MEM_RECORD_INODE:
                        panic("hammer_sync_record_callback: attempt to "
                              "sync inode record %p?", record);
                        break; /* NOT REACHED */
                case HAMMER_MEM_RECORD_DEL:
                        /* 
                         * Follow through and issue the on-disk deletion
                         */
                        break;
                }
        }

        /*
         * If DELETED_FE is set special handling is needed for directory
         * entries.  Dependant pieces related to the directory entry may
         * have already been synced to disk.  If this occurs we have to
         * sync the directory entry and then change the in-memory record
         * from an ADD to a DELETE to cover the fact that it's been
         * deleted by the frontend.
         *
         * A directory delete covering record (MEM_RECORD_DEL) can never
         * be deleted by the frontend.
         *
         * Any other record type (aka DATA) can be deleted by the frontend.
         * XXX At the moment the flusher must skip it because there may
         * be another data record in the flush group for the same block,
         * meaning that some frontend data changes can leak into the backend's
         * synchronization point.
         */
        if (record->flags & HAMMER_RECF_DELETED_FE) {
                if (record->type == HAMMER_MEM_RECORD_ADD) {
                        /*
                         * Convert a front-end deleted directory-add to
                         * a directory-delete entry later.
                         */
                        record->flags |= HAMMER_RECF_CONVERT_DELETE;
                } else {
                        /*
                         * Dispose of the record (race case).  Mark as
                         * deleted by backend (and not committed).
                         */
                        KKASSERT(record->type != HAMMER_MEM_RECORD_DEL);
                        record->flags |= HAMMER_RECF_DELETED_BE;
                        ++record->ip->rec_generation;
                        error = 0;
                        goto done;
                }
        }

        /*
         * Assign the create_tid for new records.  Deletions already
         * have the record's entire key properly set up.
         */
        if (record->type != HAMMER_MEM_RECORD_DEL) {
                record->leaf.base.create_tid = trans->tid;
                record->leaf.create_ts = trans->time32;
        }

        /*
         * This actually moves the record to the on-media B-Tree.  We
         * must also generate REDO_TERM entries in the UNDO/REDO FIFO
         * indicating that the related REDO_WRITE(s) have been committed.
         *
         * During recovery any REDO_TERM's within the nominal recovery span
         * are ignored since the related meta-data is being undone, causing
         * any matching REDO_WRITEs to execute.  The REDO_TERMs outside
         * the nominal recovery span will match against REDO_WRITEs and
         * prevent them from being executed (because the meta-data has
         * already been synchronized).
         */
        if (record->flags & HAMMER_RECF_REDO) {
                KKASSERT(record->type == HAMMER_MEM_RECORD_DATA);
                hammer_generate_redo(trans, record->ip,
                                     record->leaf.base.key -
                                         record->leaf.data_len,
                                     HAMMER_REDO_TERM_WRITE,
                                     NULL,
                                     record->leaf.data_len);
        }

        for (;;) {
                error = hammer_ip_sync_record_cursor(cursor, record);
                if (error != EDEADLK)
                        break;
                hammer_done_cursor(cursor);
                error = hammer_init_cursor(trans, cursor, &record->ip->cache[0],
                                           record->ip);
                if (error)
                        break;
        }
        record->flags &= ~HAMMER_RECF_CONVERT_DELETE;

        if (error)
                error = -error;
done:
        hammer_flush_record_done(record, error);

        /*
         * Do partial finalization if we have built up too many dirty
         * buffers.  Otherwise a buffer cache deadlock can occur when
         * doing things like creating tens of thousands of tiny files.
         *
         * We must release our cursor lock to avoid a 3-way deadlock
         * due to the exclusive sync lock the finalizer must get.
         *
         * WARNING: See warnings in hammer_unlock_cursor() function.
         */
        if (hammer_flusher_meta_limit(hmp) ||
            vm_page_count_severe()) {
                hammer_unlock_cursor(cursor);
                hammer_flusher_finalize(trans, 0);
                hammer_lock_cursor(cursor);
        }
        return(error);
}

/*
 * Backend function called by the flusher to sync an inode to media.
 */
int
hammer_sync_inode(hammer_transaction_t trans, hammer_inode_t ip)
{
        struct hammer_cursor cursor;
        hammer_node_t tmp_node;
        hammer_record_t depend;
        hammer_record_t next;
        int error, tmp_error;
        u_int64_t nlinks;

        if ((ip->sync_flags & HAMMER_INODE_MODMASK) == 0)
                return(0);

        error = hammer_init_cursor(trans, &cursor, &ip->cache[1], ip);
        if (error)
                goto done;

        /*
         * Any directory records referencing this inode which are not in
         * our current flush group must adjust our nlink count for the
         * purposes of synchronizating to disk.
         *
         * Records which are in our flush group can be unlinked from our
         * inode now, potentially allowing the inode to be physically
         * deleted.
         *
         * This cannot block.
         */
        nlinks = ip->ino_data.nlinks;
        next = TAILQ_FIRST(&ip->target_list);
        while ((depend = next) != NULL) {
                next = TAILQ_NEXT(depend, target_entry);
                if (depend->flush_state == HAMMER_FST_FLUSH &&
                    depend->flush_group == ip->flush_group) {
                        /*
                         * If this is an ADD that was deleted by the frontend
                         * the frontend nlinks count will have already been
                         * decremented, but the backend is going to sync its
                         * directory entry and must account for it.  The
                         * record will be converted to a delete-on-disk when
                         * it gets synced.
                         *
                         * If the ADD was not deleted by the frontend we
                         * can remove the dependancy from our target_list.
                         */
                        if (depend->flags & HAMMER_RECF_DELETED_FE) {
                                ++nlinks;
                        } else {
                                TAILQ_REMOVE(&ip->target_list, depend,
                                             target_entry);
                                depend->target_ip = NULL;
                        }
                } else if ((depend->flags & HAMMER_RECF_DELETED_FE) == 0) {
                        /*
                         * Not part of our flush group and not deleted by
                         * the front-end, adjust the link count synced to
                         * the media (undo what the frontend did when it
                         * queued the record).
                         */
                        KKASSERT((depend->flags & HAMMER_RECF_DELETED_BE) == 0);
                        switch(depend->type) {
                        case HAMMER_MEM_RECORD_ADD:
                                --nlinks;
                                break;
                        case HAMMER_MEM_RECORD_DEL:
                                ++nlinks;
                                break;
                        default:
                                break;
                        }
                }
        }

        /*
         * Set dirty if we had to modify the link count.
         */
        if (ip->sync_ino_data.nlinks != nlinks) {
                KKASSERT((int64_t)nlinks >= 0);
                ip->sync_ino_data.nlinks = nlinks;
                ip->sync_flags |= HAMMER_INODE_DDIRTY;
        }

        /*
         * If there is a trunction queued destroy any data past the (aligned)
         * truncation point.  Userland will have dealt with the buffer
         * containing the truncation point for us.
         *
         * We don't flush pending frontend data buffers until after we've
         * dealt with the truncation.
         */
        if (ip->sync_flags & HAMMER_INODE_TRUNCATED) {
                /*
                 * Interlock trunc_off.  The VOP front-end may continue to
                 * make adjustments to it while we are blocked.
                 */
                off_t trunc_off;
                off_t aligned_trunc_off;
                int blkmask;

                trunc_off = ip->sync_trunc_off;
                blkmask = hammer_blocksize(trunc_off) - 1;
                aligned_trunc_off = (trunc_off + blkmask) & ~(int64_t)blkmask;

                /*
                 * Delete any whole blocks on-media.  The front-end has
                 * already cleaned out any partial block and made it
                 * pending.  The front-end may have updated trunc_off
                 * while we were blocked so we only use sync_trunc_off.
                 *
                 * This operation can blow out the buffer cache, EWOULDBLOCK
                 * means we were unable to complete the deletion.  The
                 * deletion will update sync_trunc_off in that case.
                 */
                error = hammer_ip_delete_range(&cursor, ip,
                                                aligned_trunc_off,
                                                0x7FFFFFFFFFFFFFFFLL, 2);
                if (error == EWOULDBLOCK) {
                        ip->flags |= HAMMER_INODE_WOULDBLOCK;
                        error = 0;
                        goto defer_buffer_flush;
                }

                if (error)
                        goto done;

                /*
                 * Generate a REDO_TERM_TRUNC entry in the UNDO/REDO FIFO.
                 *
                 * XXX we do this even if we did not previously generate
                 * a REDO_TRUNC record.  This operation may enclosed the
                 * range for multiple prior truncation entries in the REDO
                 * log.
                 */
                if (trans->hmp->version >= HAMMER_VOL_VERSION_FOUR &&
                    (ip->flags & HAMMER_INODE_RDIRTY)) {
                        hammer_generate_redo(trans, ip, aligned_trunc_off,
                                             HAMMER_REDO_TERM_TRUNC,
                                             NULL, 0);
                }

                /*
                 * Clear the truncation flag on the backend after we have
                 * completed the deletions.  Backend data is now good again
                 * (including new records we are about to sync, below).
                 *
                 * Leave sync_trunc_off intact.  As we write additional
                 * records the backend will update sync_trunc_off.  This
                 * tells the backend whether it can skip the overwrite
                 * test.  This should work properly even when the backend
                 * writes full blocks where the truncation point straddles
                 * the block because the comparison is against the base
                 * offset of the record.
                 */
                ip->sync_flags &= ~HAMMER_INODE_TRUNCATED;
                /* ip->sync_trunc_off = 0x7FFFFFFFFFFFFFFFLL; */
        } else {
                error = 0;
        }

        /*
         * Now sync related records.  These will typically be directory
         * entries, records tracking direct-writes, or delete-on-disk records.
         */
        if (error == 0) {
                tmp_error = RB_SCAN(hammer_rec_rb_tree, &ip->rec_tree, NULL,
                                    hammer_sync_record_callback, &cursor);
                if (tmp_error < 0)
                        tmp_error = -error;
                if (tmp_error)
                        error = tmp_error;
        }
        hammer_cache_node(&ip->cache[1], cursor.node);

        /*
         * Re-seek for inode update, assuming our cache hasn't been ripped
         * out from under us.
         */
        if (error == 0) {
                tmp_node = hammer_ref_node_safe(trans, &ip->cache[0], &error);
                if (tmp_node) {
                        hammer_cursor_downgrade(&cursor);
                        hammer_lock_sh(&tmp_node->lock);
                        if ((tmp_node->flags & HAMMER_NODE_DELETED) == 0)
                                hammer_cursor_seek(&cursor, tmp_node, 0);
                        hammer_unlock(&tmp_node->lock);
                        hammer_rel_node(tmp_node);
                }
                error = 0;
        }

        /*
         * If we are deleting the inode the frontend had better not have
         * any active references on elements making up the inode.
         *
         * The call to hammer_ip_delete_clean() cleans up auxillary records
         * but not DB or DATA records.  Those must have already been deleted
         * by the normal truncation mechanic.
         */
        if (error == 0 && ip->sync_ino_data.nlinks == 0 &&
                RB_EMPTY(&ip->rec_tree)  &&
            (ip->sync_flags & HAMMER_INODE_DELETING) &&
            (ip->flags & HAMMER_INODE_DELETED) == 0) {
                int count1 = 0;

                error = hammer_ip_delete_clean(&cursor, ip, &count1);
                if (error == 0) {
                        ip->flags |= HAMMER_INODE_DELETED;
                        ip->sync_flags &= ~HAMMER_INODE_DELETING;
                        ip->sync_flags &= ~HAMMER_INODE_TRUNCATED;
                        KKASSERT(RB_EMPTY(&ip->rec_tree));

                        /*
                         * Set delete_tid in both the frontend and backend
                         * copy of the inode record.  The DELETED flag handles
                         * this, do not set DDIRTY.
                         */
                        ip->ino_leaf.base.delete_tid = trans->tid;
                        ip->sync_ino_leaf.base.delete_tid = trans->tid;
                        ip->ino_leaf.delete_ts = trans->time32;
                        ip->sync_ino_leaf.delete_ts = trans->time32;


                        /*
                         * Adjust the inode count in the volume header
                         */
                        hammer_sync_lock_sh(trans);
                        if (ip->flags & HAMMER_INODE_ONDISK) {
                                hammer_modify_volume_field(trans,
                                                           trans->rootvol,
                                                           vol0_stat_inodes);
                                --ip->hmp->rootvol->ondisk->vol0_stat_inodes;
                                hammer_modify_volume_done(trans->rootvol);
                        }
                        hammer_sync_unlock(trans);
                }
        }

        if (error)
                goto done;
        ip->sync_flags &= ~HAMMER_INODE_BUFS;

defer_buffer_flush:
        /*
         * Now update the inode's on-disk inode-data and/or on-disk record.
         * DELETED and ONDISK are managed only in ip->flags.
         *
         * In the case of a defered buffer flush we still update the on-disk
         * inode to satisfy visibility requirements if there happen to be
         * directory dependancies.
         */
        switch(ip->flags & (HAMMER_INODE_DELETED | HAMMER_INODE_ONDISK)) {
        case HAMMER_INODE_DELETED|HAMMER_INODE_ONDISK:
                /*
                 * If deleted and on-disk, don't set any additional flags.
                 * the delete flag takes care of things.
                 *
                 * Clear flags which may have been set by the frontend.
                 */
                ip->sync_flags &= ~(HAMMER_INODE_DDIRTY | HAMMER_INODE_XDIRTY |
                                    HAMMER_INODE_SDIRTY |
                                    HAMMER_INODE_ATIME | HAMMER_INODE_MTIME |
                                    HAMMER_INODE_DELETING);
                break;
        case HAMMER_INODE_DELETED:
                /*
                 * Take care of the case where a deleted inode was never
                 * flushed to the disk in the first place.
                 *
                 * Clear flags which may have been set by the frontend.
                 */
                ip->sync_flags &= ~(HAMMER_INODE_DDIRTY | HAMMER_INODE_XDIRTY |
                                    HAMMER_INODE_SDIRTY |
                                    HAMMER_INODE_ATIME | HAMMER_INODE_MTIME |
                                    HAMMER_INODE_DELETING);
                while (RB_ROOT(&ip->rec_tree)) {
                        hammer_record_t record = RB_ROOT(&ip->rec_tree);
                        hammer_ref(&record->lock);
                        KKASSERT(hammer_oneref(&record->lock));
                        record->flags |= HAMMER_RECF_DELETED_BE;
                        ++record->ip->rec_generation;
                        hammer_rel_mem_record(record);
                }
                break;
        case HAMMER_INODE_ONDISK:
                /*
                 * If already on-disk, do not set any additional flags.
                 */
                break;
        default:
                /*
                 * If not on-disk and not deleted, set DDIRTY to force
                 * an initial record to be written.
                 *
                 * Also set the create_tid in both the frontend and backend
                 * copy of the inode record.
                 */
                ip->ino_leaf.base.create_tid = trans->tid;
                ip->ino_leaf.create_ts = trans->time32;
                ip->sync_ino_leaf.base.create_tid = trans->tid;
                ip->sync_ino_leaf.create_ts = trans->time32;
                ip->sync_flags |= HAMMER_INODE_DDIRTY;
                break;
        }

        /*
         * If DDIRTY or SDIRTY is set, write out a new record.
         * If the inode is already on-disk the old record is marked as
         * deleted.
         *
         * If DELETED is set hammer_update_inode() will delete the existing
         * record without writing out a new one.
         *
         * If *ONLY* the ITIMES flag is set we can update the record in-place.
         */
        if (ip->flags & HAMMER_INODE_DELETED) {
                error = hammer_update_inode(&cursor, ip);
        } else 
        if (!(ip->sync_flags & (HAMMER_INODE_DDIRTY | HAMMER_INODE_SDIRTY)) &&
            (ip->sync_flags & (HAMMER_INODE_ATIME | HAMMER_INODE_MTIME))) {
                error = hammer_update_itimes(&cursor, ip);
        } else
        if (ip->sync_flags & (HAMMER_INODE_DDIRTY | HAMMER_INODE_SDIRTY |
                              HAMMER_INODE_ATIME | HAMMER_INODE_MTIME)) {
                error = hammer_update_inode(&cursor, ip);
        }
done:
        if (ip->flags & HAMMER_INODE_MODMASK)
                hammer_inode_dirty(ip);
        if (error) {
                hammer_critical_error(ip->hmp, ip, error,
                                      "while syncing inode");
        }
        hammer_done_cursor(&cursor);
        return(error);
}

/*
 * This routine is called when the OS is no longer actively referencing
 * the inode (but might still be keeping it cached), or when releasing
 * the last reference to an inode.
 *
 * At this point if the inode's nlinks count is zero we want to destroy
 * it, which may mean destroying it on-media too.
 */
void
hammer_inode_unloadable_check(hammer_inode_t ip, int getvp)
{
        struct vnode *vp;

        /*
         * Set the DELETING flag when the link count drops to 0 and the
         * OS no longer has any opens on the inode.
         *
         * The backend will clear DELETING (a mod flag) and set DELETED
         * (a state flag) when it is actually able to perform the
         * operation.
         *
         * Don't reflag the deletion if the flusher is currently syncing
         * one that was already flagged.  A previously set DELETING flag
         * may bounce around flags and sync_flags until the operation is
         * completely done.
         *
         * Do not attempt to modify a snapshot inode (one set to read-only).
         */
        if (ip->ino_data.nlinks == 0 &&
            ((ip->flags | ip->sync_flags) & (HAMMER_INODE_RO|HAMMER_INODE_DELETING|HAMMER_INODE_DELETED)) == 0) {
                ip->flags |= HAMMER_INODE_DELETING;
                ip->flags |= HAMMER_INODE_TRUNCATED;
                ip->trunc_off = 0;
                vp = NULL;
                if (getvp) {
                        if (hammer_get_vnode(ip, &vp) != 0)
                                return;
                }

                /*
                 * Final cleanup
                 */
                if (ip->vp)
                        nvtruncbuf(ip->vp, 0, HAMMER_BUFSIZE, 0, 0);
                if (ip->flags & HAMMER_INODE_MODMASK)
                        hammer_inode_dirty(ip);
                if (getvp)
                        vput(vp);
        }
}

/*
 * After potentially resolving a dependancy the inode is tested
 * to determine whether it needs to be reflushed.
 */
void
hammer_test_inode(hammer_inode_t ip)
{
        if (ip->flags & HAMMER_INODE_REFLUSH) {
                ip->flags &= ~HAMMER_INODE_REFLUSH;
                hammer_ref(&ip->lock);
                if (ip->flags & HAMMER_INODE_RESIGNAL) {
                        ip->flags &= ~HAMMER_INODE_RESIGNAL;
                        hammer_flush_inode(ip, HAMMER_FLUSH_SIGNAL);
                } else {
                        hammer_flush_inode(ip, 0);
                }
                hammer_rel_inode(ip, 0);
        }
}

/*
 * Clear the RECLAIM flag on an inode.  This occurs when the inode is
 * reassociated with a vp or just before it gets freed.
 *
 * Pipeline wakeups to threads blocked due to an excessive number of
 * detached inodes.  This typically occurs when atime updates accumulate
 * while scanning a directory tree.
 */
static void
hammer_inode_wakereclaims(hammer_inode_t ip)
{
        struct hammer_reclaim *reclaim;
        hammer_mount_t hmp = ip->hmp;

        if ((ip->flags & HAMMER_INODE_RECLAIM) == 0)
                return;

        --hammer_count_reclaims;
        --hmp->count_reclaims;
        ip->flags &= ~HAMMER_INODE_RECLAIM;

        if ((reclaim = TAILQ_FIRST(&hmp->reclaim_list)) != NULL) {
                KKASSERT(reclaim->count > 0);
                if (--reclaim->count == 0) {
                        TAILQ_REMOVE(&hmp->reclaim_list, reclaim, entry);
                        wakeup(reclaim);
                }
        }
}

/*
 * Setup our reclaim pipeline.  We only let so many detached (and dirty)
 * inodes build up before we start blocking.  This routine is called
 * if a new inode is created or an inode is loaded from media.
 *
 * When we block we don't care *which* inode has finished reclaiming,
 * as long as one does.
 *
 * The reclaim pipeline is primarily governed by the auto-flush which is
 * 1/4 hammer_limit_reclaims.  We don't want to block if the count is
 * less than 1/2 hammer_limit_reclaims.  From 1/2 to full count is
 * dynamically governed.
 */
void
hammer_inode_waitreclaims(hammer_transaction_t trans)
{
        hammer_mount_t hmp = trans->hmp;
        struct hammer_reclaim reclaim;
        int lower_limit;

        /*
         * Track inode load, delay if the number of reclaiming inodes is
         * between 2/4 and 4/4 hammer_limit_reclaims, depending.
         */
        if (curthread->td_proc) {
                struct hammer_inostats *stats;

                stats = hammer_inode_inostats(hmp, curthread->td_proc->p_pid);
                ++stats->count;

                if (stats->count > hammer_limit_reclaims / 2)
                        stats->count = hammer_limit_reclaims / 2;
                lower_limit = hammer_limit_reclaims - stats->count;
                if (hammer_debug_general & 0x10000) {
                        kprintf("pid %5d limit %d\n",
                                (int)curthread->td_proc->p_pid, lower_limit);
                }
        } else {
                lower_limit = hammer_limit_reclaims * 3 / 4;
        }
        if (hmp->count_reclaims >= lower_limit) {
                reclaim.count = 1;
                TAILQ_INSERT_TAIL(&hmp->reclaim_list, &reclaim, entry);
                tsleep(&reclaim, 0, "hmrrcm", hz);
                if (reclaim.count > 0)
                        TAILQ_REMOVE(&hmp->reclaim_list, &reclaim, entry);
        }
}

/*
 * Keep track of reclaim statistics on a per-pid basis using a loose
 * 4-way set associative hash table.  Collisions inherit the count of
 * the previous entry.
 *
 * NOTE: We want to be careful here to limit the chain size.  If the chain
 *       size is too large a pid will spread its stats out over too many
 *       entries under certain types of heavy filesystem activity and
 *       wind up not delaying long enough.
 */
static
struct hammer_inostats *
hammer_inode_inostats(hammer_mount_t hmp, pid_t pid)
{
        struct hammer_inostats *stats;
        int delta;
        int chain;
        static volatile int iterator;   /* we don't care about MP races */

        /*
         * Chain up to 4 times to find our entry.
         */
        for (chain = 0; chain < 4; ++chain) {
                stats = &hmp->inostats[(pid + chain) & HAMMER_INOSTATS_HMASK];
                if (stats->pid == pid)
                        break;
        }

        /*
         * Replace one of the four chaining entries with our new entry.
         */
        if (chain == 4) {
                stats = &hmp->inostats[(pid + (iterator++ & 3)) &
                                       HAMMER_INOSTATS_HMASK];
                stats->pid = pid;
        }

        /*
         * Decay the entry
         */
        if (stats->count && stats->ltick != ticks) {
                delta = ticks - stats->ltick;
                stats->ltick = ticks;
                if (delta <= 0 || delta > hz * 60)
                        stats->count = 0;
                else
                        stats->count = stats->count * hz / (hz + delta);
        }
        if (hammer_debug_general & 0x10000)
                kprintf("pid %5d stats %d\n", (int)pid, stats->count);
        return (stats);
}

#if 0

/*
 * XXX not used, doesn't work very well due to the large batching nature
 * of flushes.
 *
 * A larger then normal backlog of inodes is sitting in the flusher,
 * enforce a general slowdown to let it catch up.  This routine is only
 * called on completion of a non-flusher-related transaction which
 * performed B-Tree node I/O.
 *
 * It is possible for the flusher to stall in a continuous load.
 * blogbench -i1000 -o seems to do a good job generating this sort of load.
 * If the flusher is unable to catch up the inode count can bloat until
 * we run out of kvm.
 *
 * This is a bit of a hack.
 */
void
hammer_inode_waithard(hammer_mount_t hmp)
{
        /*
         * Hysteresis.
         */
        if (hmp->flags & HAMMER_MOUNT_FLUSH_RECOVERY) {
                if (hmp->count_reclaims < hammer_limit_reclaims / 2 &&
                    hmp->count_iqueued < hmp->count_inodes / 20) {
                        hmp->flags &= ~HAMMER_MOUNT_FLUSH_RECOVERY;
                        return;
                }
        } else {
                if (hmp->count_reclaims < hammer_limit_reclaims ||
                    hmp->count_iqueued < hmp->count_inodes / 10) {
                        return;
                }
                hmp->flags |= HAMMER_MOUNT_FLUSH_RECOVERY;
        }

        /*
         * Block for one flush cycle.
         */
        hammer_flusher_wait_next(hmp);
}

#endif