hammer2 - Allow chains to be cached

[dragonfly.git] / sys / vfs / hammer2 / hammer2_vfsops.c

/*
 * Copyright (c) 2011-2015 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * by Daniel Flores (GSOC 2013 - mentored by Matthew Dillon, compression)
 *
 * 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/nlookup.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/fcntl.h>
#include <sys/buf.h>
#include <sys/uuid.h>
#include <sys/vfsops.h>
#include <sys/sysctl.h>
#include <sys/socket.h>
#include <sys/objcache.h>

#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/mountctl.h>
#include <sys/dirent.h>
#include <sys/uio.h>

#include <sys/mutex.h>
#include <sys/mutex2.h>

#include "hammer2.h"
#include "hammer2_disk.h"
#include "hammer2_mount.h"
#include "hammer2_lz4.h"

#include "zlib/hammer2_zlib.h"

#define REPORT_REFS_ERRORS 1    /* XXX remove me */

MALLOC_DEFINE(M_OBJCACHE, "objcache", "Object Cache");

struct hammer2_sync_info {
        int error;
        int waitfor;
};

TAILQ_HEAD(hammer2_mntlist, hammer2_dev);
TAILQ_HEAD(hammer2_pfslist, hammer2_pfs);
static struct hammer2_mntlist hammer2_mntlist;
static struct hammer2_pfslist hammer2_pfslist;
static struct lock hammer2_mntlk;

int hammer2_debug;
int hammer2_cluster_enable = 4;
int hammer2_hardlink_enable = 1;
int hammer2_flush_pipe = 100;
int hammer2_synchronous_flush = 1;
int hammer2_dio_count;
long hammer2_chain_allocs;
long hammer2_chain_frees;
long hammer2_limit_dirty_chains;
long hammer2_count_modified_chains;
long hammer2_iod_file_read;
long hammer2_iod_meta_read;
long hammer2_iod_indr_read;
long hammer2_iod_fmap_read;
long hammer2_iod_volu_read;
long hammer2_iod_file_write;
long hammer2_iod_file_wembed;
long hammer2_iod_file_wzero;
long hammer2_iod_file_wdedup;
long hammer2_iod_meta_write;
long hammer2_iod_indr_write;
long hammer2_iod_fmap_write;
long hammer2_iod_volu_write;
long hammer2_ioa_file_read;
long hammer2_ioa_meta_read;
long hammer2_ioa_indr_read;
long hammer2_ioa_fmap_read;
long hammer2_ioa_volu_read;
long hammer2_ioa_fmap_write;
long hammer2_ioa_file_write;
long hammer2_ioa_meta_write;
long hammer2_ioa_indr_write;
long hammer2_ioa_volu_write;

MALLOC_DECLARE(M_HAMMER2_CBUFFER);
MALLOC_DEFINE(M_HAMMER2_CBUFFER, "HAMMER2-compbuffer",
                "Buffer used for compression.");

MALLOC_DECLARE(M_HAMMER2_DEBUFFER);
MALLOC_DEFINE(M_HAMMER2_DEBUFFER, "HAMMER2-decompbuffer",
                "Buffer used for decompression.");

SYSCTL_NODE(_vfs, OID_AUTO, hammer2, CTLFLAG_RW, 0, "HAMMER2 filesystem");

SYSCTL_INT(_vfs_hammer2, OID_AUTO, debug, CTLFLAG_RW,
           &hammer2_debug, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, cluster_enable, CTLFLAG_RW,
           &hammer2_cluster_enable, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, hardlink_enable, CTLFLAG_RW,
           &hammer2_hardlink_enable, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, flush_pipe, CTLFLAG_RW,
           &hammer2_flush_pipe, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, synchronous_flush, CTLFLAG_RW,
           &hammer2_synchronous_flush, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, chain_allocs, CTLFLAG_RW,
           &hammer2_chain_allocs, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, chain_frees, CTLFLAG_RW,
           &hammer2_chain_frees, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, limit_dirty_chains, CTLFLAG_RW,
           &hammer2_limit_dirty_chains, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, count_modified_chains, CTLFLAG_RW,
           &hammer2_count_modified_chains, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, dio_count, CTLFLAG_RD,
           &hammer2_dio_count, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_read, CTLFLAG_RW,
           &hammer2_iod_file_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_meta_read, CTLFLAG_RW,
           &hammer2_iod_meta_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_indr_read, CTLFLAG_RW,
           &hammer2_iod_indr_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_fmap_read, CTLFLAG_RW,
           &hammer2_iod_fmap_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_volu_read, CTLFLAG_RW,
           &hammer2_iod_volu_read, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_write, CTLFLAG_RW,
           &hammer2_iod_file_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wembed, CTLFLAG_RW,
           &hammer2_iod_file_wembed, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wzero, CTLFLAG_RW,
           &hammer2_iod_file_wzero, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wdedup, CTLFLAG_RW,
           &hammer2_iod_file_wdedup, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_meta_write, CTLFLAG_RW,
           &hammer2_iod_meta_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_indr_write, CTLFLAG_RW,
           &hammer2_iod_indr_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_fmap_write, CTLFLAG_RW,
           &hammer2_iod_fmap_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_volu_write, CTLFLAG_RW,
           &hammer2_iod_volu_write, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_file_read, CTLFLAG_RW,
           &hammer2_ioa_file_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_meta_read, CTLFLAG_RW,
           &hammer2_ioa_meta_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_indr_read, CTLFLAG_RW,
           &hammer2_ioa_indr_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_fmap_read, CTLFLAG_RW,
           &hammer2_ioa_fmap_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_volu_read, CTLFLAG_RW,
           &hammer2_ioa_volu_read, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_file_write, CTLFLAG_RW,
           &hammer2_ioa_file_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_meta_write, CTLFLAG_RW,
           &hammer2_ioa_meta_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_indr_write, CTLFLAG_RW,
           &hammer2_ioa_indr_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_fmap_write, CTLFLAG_RW,
           &hammer2_ioa_fmap_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_volu_write, CTLFLAG_RW,
           &hammer2_ioa_volu_write, 0, "");

long hammer2_check_icrc32;
long hammer2_check_xxhash64;
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, check_icrc32, CTLFLAG_RW,
           &hammer2_check_icrc32, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, check_xxhash64, CTLFLAG_RW,
           &hammer2_check_xxhash64, 0, "");

static int hammer2_vfs_init(struct vfsconf *conf);
static int hammer2_vfs_uninit(struct vfsconf *vfsp);
static int hammer2_vfs_mount(struct mount *mp, char *path, caddr_t data,
                                struct ucred *cred);
static int hammer2_remount(hammer2_dev_t *, struct mount *, char *,
                                struct vnode *, struct ucred *);
static int hammer2_recovery(hammer2_dev_t *hmp);
static int hammer2_vfs_unmount(struct mount *mp, int mntflags);
static int hammer2_vfs_root(struct mount *mp, struct vnode **vpp);
static int hammer2_vfs_statfs(struct mount *mp, struct statfs *sbp,
                                struct ucred *cred);
static int hammer2_vfs_statvfs(struct mount *mp, struct statvfs *sbp,
                                struct ucred *cred);
static int hammer2_vfs_vget(struct mount *mp, struct vnode *dvp,
                                ino_t ino, struct vnode **vpp);
static int hammer2_vfs_fhtovp(struct mount *mp, struct vnode *rootvp,
                                struct fid *fhp, struct vnode **vpp);
static int hammer2_vfs_vptofh(struct vnode *vp, struct fid *fhp);
static int hammer2_vfs_checkexp(struct mount *mp, struct sockaddr *nam,
                                int *exflagsp, struct ucred **credanonp);

static int hammer2_install_volume_header(hammer2_dev_t *hmp);
static int hammer2_sync_scan2(struct mount *mp, struct vnode *vp, void *data);

static void hammer2_update_pmps(hammer2_dev_t *hmp);

static void hammer2_mount_helper(struct mount *mp, hammer2_pfs_t *pmp);
static void hammer2_unmount_helper(struct mount *mp, hammer2_pfs_t *pmp,
                                hammer2_dev_t *hmp);

/*
 * HAMMER2 vfs operations.
 */
static struct vfsops hammer2_vfsops = {
        .vfs_init       = hammer2_vfs_init,
        .vfs_uninit     = hammer2_vfs_uninit,
        .vfs_sync       = hammer2_vfs_sync,
        .vfs_mount      = hammer2_vfs_mount,
        .vfs_unmount    = hammer2_vfs_unmount,
        .vfs_root       = hammer2_vfs_root,
        .vfs_statfs     = hammer2_vfs_statfs,
        .vfs_statvfs    = hammer2_vfs_statvfs,
        .vfs_vget       = hammer2_vfs_vget,
        .vfs_vptofh     = hammer2_vfs_vptofh,
        .vfs_fhtovp     = hammer2_vfs_fhtovp,
        .vfs_checkexp   = hammer2_vfs_checkexp
};

MALLOC_DEFINE(M_HAMMER2, "HAMMER2-mount", "");

VFS_SET(hammer2_vfsops, hammer2, 0);
MODULE_VERSION(hammer2, 1);

static
int
hammer2_vfs_init(struct vfsconf *conf)
{
        static struct objcache_malloc_args margs_read;
        static struct objcache_malloc_args margs_write;
        static struct objcache_malloc_args margs_vop;

        int error;

        error = 0;

        if (HAMMER2_BLOCKREF_BYTES != sizeof(struct hammer2_blockref))
                error = EINVAL;
        if (HAMMER2_INODE_BYTES != sizeof(struct hammer2_inode_data))
                error = EINVAL;
        if (HAMMER2_VOLUME_BYTES != sizeof(struct hammer2_volume_data))
                error = EINVAL;

        if (error)
                kprintf("HAMMER2 structure size mismatch; cannot continue.\n");
        
        margs_read.objsize = 65536;
        margs_read.mtype = M_HAMMER2_DEBUFFER;
        
        margs_write.objsize = 32768;
        margs_write.mtype = M_HAMMER2_CBUFFER;

        margs_vop.objsize = sizeof(hammer2_xop_t);
        margs_vop.mtype = M_HAMMER2;
        
        /*
         * Note thaht for the XOPS cache we want backing store allocations
         * to use M_ZERO.  This is not allowed in objcache_get() (to avoid
         * confusion), so use the backing store function that does it.  This
         * means that initial XOPS objects are zerod but REUSED objects are
         * not.  So we are responsible for cleaning the object up sufficiently
         * for our needs before objcache_put()ing it back (typically just the
         * FIFO indices).
         */
        cache_buffer_read = objcache_create(margs_read.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc,
                                objcache_malloc_free,
                                &margs_read);
        cache_buffer_write = objcache_create(margs_write.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc,
                                objcache_malloc_free,
                                &margs_write);
        cache_xops = objcache_create(margs_vop.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc_zero,
                                objcache_malloc_free,
                                &margs_vop);


        lockinit(&hammer2_mntlk, "mntlk", 0, 0);
        TAILQ_INIT(&hammer2_mntlist);
        TAILQ_INIT(&hammer2_pfslist);

        hammer2_limit_dirty_chains = desiredvnodes / 10;

        return (error);
}

static
int
hammer2_vfs_uninit(struct vfsconf *vfsp __unused)
{
        objcache_destroy(cache_buffer_read);
        objcache_destroy(cache_buffer_write);
        objcache_destroy(cache_xops);
        return 0;
}

/*
 * Core PFS allocator.  Used to allocate the pmp structure for PFS cluster
 * mounts and the spmp structure for media (hmp) structures.
 *
 * pmp->modify_tid tracks new modify_tid transaction ids for front-end
 * transactions.  Note that synchronization does not use this field.
 * (typically frontend operations and synchronization cannot run on the
 * same PFS node at the same time).
 *
 * XXX check locking
 */
hammer2_pfs_t *
hammer2_pfsalloc(hammer2_chain_t *chain, const hammer2_inode_data_t *ripdata,
                 hammer2_tid_t modify_tid, hammer2_dev_t *force_local)
{
        hammer2_inode_t *iroot;
        hammer2_pfs_t *pmp;
        int count;
        int i;
        int j;

        /*
         * Locate or create the PFS based on the cluster id.  If ripdata
         * is NULL this is a spmp which is unique and is always allocated.
         *
         * If the device is mounted in local mode all PFSs are considered
         * independent and not part of any cluster (for debugging only).
         */
        if (ripdata) {
                TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                        if (force_local != pmp->force_local)
                                continue;
                        if (force_local == NULL &&
                            bcmp(&pmp->pfs_clid, &ripdata->meta.pfs_clid,
                                 sizeof(pmp->pfs_clid)) == 0) {
                                        break;
                        } else if (force_local && pmp->pfs_names[0] &&
                            strcmp(pmp->pfs_names[0], ripdata->filename) == 0) {
                                        break;
                        }
                }
        } else {
                pmp = NULL;
        }

        if (pmp == NULL) {
                pmp = kmalloc(sizeof(*pmp), M_HAMMER2, M_WAITOK | M_ZERO);
                pmp->force_local = force_local;
                hammer2_trans_manage_init(pmp);
                kmalloc_create(&pmp->minode, "HAMMER2-inodes");
                kmalloc_create(&pmp->mmsg, "HAMMER2-pfsmsg");
                lockinit(&pmp->lock, "pfslk", 0, 0);
                lockinit(&pmp->lock_nlink, "h2nlink", 0, 0);
                spin_init(&pmp->inum_spin, "hm2pfsalloc_inum");
                spin_init(&pmp->xop_spin, "h2xop");
                spin_init(&pmp->lru_spin, "h2lru");
                RB_INIT(&pmp->inum_tree);
                TAILQ_INIT(&pmp->sideq);
                TAILQ_INIT(&pmp->lru_list);
                spin_init(&pmp->list_spin, "hm2pfsalloc_list");

                /*
                 * Distribute backend operations to threads
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        for (j = 0; j < HAMMER2_XOPGROUPS +
                                        HAMMER2_SPECTHREADS; ++j) {
                                TAILQ_INIT(&pmp->xopq[i][j]);
                        }
                }
                for (i = 0; i < HAMMER2_XOPGROUPS; ++i)
                        hammer2_xop_group_init(pmp, &pmp->xop_groups[i]);

                /*
                 * Save the last media transaction id for the flusher.  Set
                 * initial 
                 */
                if (ripdata)
                        pmp->pfs_clid = ripdata->meta.pfs_clid;
                TAILQ_INSERT_TAIL(&hammer2_pfslist, pmp, mntentry);

                /*
                 * The synchronization thread may start too early, make
                 * sure it stays frozen until we are ready to let it go.
                 * XXX
                 */
                /*
                pmp->primary_thr.flags = HAMMER2_THREAD_FROZEN |
                                         HAMMER2_THREAD_REMASTER;
                */
        }

        /*
         * Create the PFS's root inode.
         */
        if ((iroot = pmp->iroot) == NULL) {
                iroot = hammer2_inode_get(pmp, NULL, NULL, -1);
                pmp->iroot = iroot;
                hammer2_inode_ref(iroot);
                hammer2_inode_unlock(iroot);
        }

        /*
         * Stop here if no chain is passed in.
         */
        if (chain == NULL)
                goto done;

        /*
         * When a chain is passed in we must add it to the PFS's root
         * inode, update pmp->pfs_types[], and update the syncronization
         * threads.
         *
         * When forcing local mode, mark the PFS as a MASTER regardless.
         *
         * At the moment empty spots can develop due to removals or failures.
         * Ultimately we want to re-fill these spots but doing so might
         * confused running code. XXX
         */
        hammer2_inode_ref(iroot);
        hammer2_mtx_ex(&iroot->lock);
        j = iroot->cluster.nchains;

        kprintf("add PFS to pmp %p[%d]\n", pmp, j);

        if (j == HAMMER2_MAXCLUSTER) {
                kprintf("hammer2_mount: cluster full!\n");
                /* XXX fatal error? */
        } else {
                KKASSERT(chain->pmp == NULL);
                chain->pmp = pmp;
                hammer2_chain_ref(chain);
                iroot->cluster.array[j].chain = chain;
                if (force_local)
                        pmp->pfs_types[j] = HAMMER2_PFSTYPE_MASTER;
                else
                        pmp->pfs_types[j] = ripdata->meta.pfs_type;
                pmp->pfs_names[j] = kstrdup(ripdata->filename, M_HAMMER2);
                pmp->pfs_hmps[j] = chain->hmp;

                /*
                 * If the PFS is already mounted we must account
                 * for the mount_count here.
                 */
                if (pmp->mp)
                        ++chain->hmp->mount_count;

                /*
                 * May have to fixup dirty chain tracking.  Previous
                 * pmp was NULL so nothing to undo.
                 */
                if (chain->flags & HAMMER2_CHAIN_MODIFIED)
                        hammer2_pfs_memory_inc(pmp);
                ++j;
        }
        iroot->cluster.nchains = j;

        /*
         * Update nmasters from any PFS inode which is part of the cluster.
         * It is possible that this will result in a value which is too
         * high.  MASTER PFSs are authoritative for pfs_nmasters and will
         * override this value later on.
         *
         * (This informs us of masters that might not currently be
         *  discoverable by this mount).
         */
        if (ripdata && pmp->pfs_nmasters < ripdata->meta.pfs_nmasters) {
                pmp->pfs_nmasters = ripdata->meta.pfs_nmasters;
        }

        /*
         * Count visible masters.  Masters are usually added with
         * ripdata->meta.pfs_nmasters set to 1.  This detects when there
         * are more (XXX and must update the master inodes).
         */
        count = 0;
        for (i = 0; i < iroot->cluster.nchains; ++i) {
                if (pmp->pfs_types[i] == HAMMER2_PFSTYPE_MASTER)
                        ++count;
        }
        if (pmp->pfs_nmasters < count)
                pmp->pfs_nmasters = count;

        /*
         * Create missing synchronization and support threads.
         *
         * Single-node masters (including snapshots) have nothing to
         * synchronize and do not require this thread.
         *
         * Multi-node masters or any number of soft masters, slaves, copy,
         * or other PFS types need the thread.
         *
         * Each thread is responsible for its particular cluster index.
         * We use independent threads so stalls or mismatches related to
         * any given target do not affect other targets.
         */
        for (i = 0; i < iroot->cluster.nchains; ++i) {
                /*
                 * Single-node masters (including snapshots) have nothing
                 * to synchronize and will make direct xops support calls,
                 * thus they do not require this thread.
                 *
                 * Note that there can be thousands of snapshots.  We do not
                 * want to create thousands of threads.
                 */
                if (pmp->pfs_nmasters <= 1 &&
                    pmp->pfs_types[i] == HAMMER2_PFSTYPE_MASTER) {
                        continue;
                }

                /*
                 * Sync support thread
                 */
                if (pmp->sync_thrs[i].td == NULL) {
                        hammer2_thr_create(&pmp->sync_thrs[i], pmp,
                                           "h2nod", i, -1,
                                           hammer2_primary_sync_thread);
                }
        }

        /*
         * Create missing Xop threads
         */
        if (pmp->mp)
                hammer2_xop_helper_create(pmp);

        hammer2_mtx_unlock(&iroot->lock);
        hammer2_inode_drop(iroot);
done:
        return pmp;
}

/*
 * Destroy a PFS, typically only occurs after the last mount on a device
 * has gone away.
 */
static void
hammer2_pfsfree(hammer2_pfs_t *pmp)
{
        hammer2_inode_t *iroot;
        hammer2_chain_t *chain;
        int i;
        int j;

        /*
         * Cleanup our reference on iroot.  iroot is (should) not be needed
         * by the flush code.
         */
        TAILQ_REMOVE(&hammer2_pfslist, pmp, mntentry);

        iroot = pmp->iroot;
        if (iroot) {
                for (i = 0; i < iroot->cluster.nchains; ++i) {
                        hammer2_thr_delete(&pmp->sync_thrs[i]);
                        for (j = 0; j < HAMMER2_XOPGROUPS; ++j)
                                hammer2_thr_delete(&pmp->xop_groups[j].thrs[i]);
                }
#if REPORT_REFS_ERRORS
                if (pmp->iroot->refs != 1)
                        kprintf("PMP->IROOT %p REFS WRONG %d\n",
                                pmp->iroot, pmp->iroot->refs);
#else
                KKASSERT(pmp->iroot->refs == 1);
#endif
                /* ref for pmp->iroot */
                hammer2_inode_drop(pmp->iroot);
                pmp->iroot = NULL;
        }

        /*
         * Cleanup chains remaining on LRU list.
         */
        kprintf("pfsfree: %p lrucount=%d\n", pmp, pmp->lru_count);
        while ((chain = TAILQ_FIRST(&pmp->lru_list)) != NULL) {
                hammer2_chain_ref(chain);
                atomic_set_int(&chain->flags, HAMMER2_CHAIN_RELEASE);
                hammer2_chain_drop(chain);
        }

        /*
         * Free remaining pmp resources
         */
        kmalloc_destroy(&pmp->mmsg);
        kmalloc_destroy(&pmp->minode);

        kfree(pmp, M_HAMMER2);
}

/*
 * Remove all references to hmp from the pfs list.  Any PFS which becomes
 * empty is terminated and freed.
 *
 * XXX inefficient.
 */
static void
hammer2_pfsfree_scan(hammer2_dev_t *hmp)
{
        hammer2_pfs_t *pmp;
        hammer2_inode_t *iroot;
        hammer2_chain_t *rchain;
        int didfreeze;
        int i;
        int j;

again:
        TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                if ((iroot = pmp->iroot) == NULL)
                        continue;
                if (hmp->spmp == pmp) {
                        kprintf("unmount hmp %p remove spmp %p\n",
                                hmp, pmp);
                        hmp->spmp = NULL;
                }

                /*
                 * Determine if this PFS is affected.  If it is we must
                 * freeze all management threads and lock its iroot.
                 *
                 * Freezing a management thread forces it idle, operations
                 * in-progress will be aborted and it will have to start
                 * over again when unfrozen, or exit if told to exit.
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] == hmp)
                                break;
                }
                if (i != HAMMER2_MAXCLUSTER) {
                        /*
                         * Make sure all synchronization threads are locked
                         * down.
                         */
                        for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                                if (pmp->pfs_hmps[i] == NULL)
                                        continue;
                                hammer2_thr_freeze_async(&pmp->sync_thrs[i]);
                                for (j = 0; j < HAMMER2_XOPGROUPS; ++j) {
                                        hammer2_thr_freeze_async(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                        for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                                if (pmp->pfs_hmps[i] == NULL)
                                        continue;
                                hammer2_thr_freeze(&pmp->sync_thrs[i]);
                                for (j = 0; j < HAMMER2_XOPGROUPS; ++j) {
                                        hammer2_thr_freeze(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }

                        /*
                         * Lock the inode and clean out matching chains.
                         * Note that we cannot use hammer2_inode_lock_*()
                         * here because that would attempt to validate the
                         * cluster that we are in the middle of ripping
                         * apart.
                         *
                         * WARNING! We are working directly on the inodes
                         *          embedded cluster.
                         */
                        hammer2_mtx_ex(&iroot->lock);

                        /*
                         * Remove the chain from matching elements of the PFS.
                         */
                        for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                                if (pmp->pfs_hmps[i] != hmp)
                                        continue;
                                hammer2_thr_delete(&pmp->sync_thrs[i]);
                                for (j = 0; j < HAMMER2_XOPGROUPS; ++j) {
                                        hammer2_thr_delete(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                                rchain = iroot->cluster.array[i].chain;
                                iroot->cluster.array[i].chain = NULL;
                                pmp->pfs_types[i] = 0;
                                if (pmp->pfs_names[i]) {
                                        kfree(pmp->pfs_names[i], M_HAMMER2);
                                        pmp->pfs_names[i] = NULL;
                                }
                                if (rchain) {
                                        hammer2_chain_drop(rchain);
                                        /* focus hint */
                                        if (iroot->cluster.focus == rchain)
                                                iroot->cluster.focus = NULL;
                                }
                                pmp->pfs_hmps[i] = NULL;
                        }
                        hammer2_mtx_unlock(&iroot->lock);
                        didfreeze = 1;  /* remaster, unfreeze down below */
                } else {
                        didfreeze = 0;
                }

                /*
                 * Cleanup trailing chains.  Gaps may remain.
                 */
                for (i = HAMMER2_MAXCLUSTER - 1; i >= 0; --i) {
                        if (pmp->pfs_hmps[i])
                                break;
                }
                iroot->cluster.nchains = i + 1;

                /*
                 * If the PMP has no elements remaining we can destroy it.
                 * (this will transition management threads from frozen->exit).
                 */
                if (iroot->cluster.nchains == 0) {
                        kprintf("unmount hmp %p last ref to PMP=%p\n",
                                hmp, pmp);
                        hammer2_pfsfree(pmp);
                        goto again;
                }

                /*
                 * If elements still remain we need to set the REMASTER
                 * flag and unfreeze it.
                 */
                if (didfreeze) {
                        for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                                if (pmp->pfs_hmps[i] == NULL)
                                        continue;
                                hammer2_thr_remaster(&pmp->sync_thrs[i]);
                                hammer2_thr_unfreeze(&pmp->sync_thrs[i]);
                                for (j = 0; j < HAMMER2_XOPGROUPS; ++j) {
                                        hammer2_thr_remaster(
                                                &pmp->xop_groups[j].thrs[i]);
                                        hammer2_thr_unfreeze(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                }
        }
}

/*
 * Mount or remount HAMMER2 fileystem from physical media
 *
 *      mountroot
 *              mp              mount point structure
 *              path            NULL
 *              data            <unused>
 *              cred            <unused>
 *
 *      mount
 *              mp              mount point structure
 *              path            path to mount point
 *              data            pointer to argument structure in user space
 *                      volume  volume path (device@LABEL form)
 *                      hflags  user mount flags
 *              cred            user credentials
 *
 * RETURNS:     0       Success
 *              !0      error number
 */
static
int
hammer2_vfs_mount(struct mount *mp, char *path, caddr_t data,
                  struct ucred *cred)
{
        struct hammer2_mount_info info;
        hammer2_pfs_t *pmp;
        hammer2_pfs_t *spmp;
        hammer2_dev_t *hmp;
        hammer2_dev_t *force_local;
        hammer2_key_t key_next;
        hammer2_key_t key_dummy;
        hammer2_key_t lhc;
        struct vnode *devvp;
        struct nlookupdata nd;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_cluster_t *cluster;
        const hammer2_inode_data_t *ripdata;
        hammer2_blockref_t bref;
        struct file *fp;
        char devstr[MNAMELEN];
        size_t size;
        size_t done;
        char *dev;
        char *label;
        int ronly = 1;
        int error;
        int cache_index;
        int i;

        hmp = NULL;
        pmp = NULL;
        dev = NULL;
        label = NULL;
        devvp = NULL;
        cache_index = -1;

        kprintf("hammer2_mount\n");

        if (path == NULL) {
                /*
                 * Root mount
                 */
                bzero(&info, sizeof(info));
                info.cluster_fd = -1;
                ksnprintf(devstr, sizeof(devstr), "%s",
                          mp->mnt_stat.f_mntfromname);
                kprintf("hammer2_mount: root '%s'\n", devstr);
        } else {
                /*
                 * Non-root mount or updating a mount
                 */
                error = copyin(data, &info, sizeof(info));
                if (error)
                        return (error);

                error = copyinstr(info.volume, devstr, MNAMELEN - 1, &done);
                if (error)
                        return (error);
        }

        /* Extract device and label */
        dev = devstr;
        label = strchr(devstr, '@');
        if (label == NULL ||
            ((label + 1) - dev) > done) {
                return (EINVAL);
        }
        *label = '\0';
        label++;
        if (*label == '\0')
                return (EINVAL);

        if (mp->mnt_flag & MNT_UPDATE) {
                /*
                 * Update mount.  Note that pmp->iroot->cluster is
                 * an inode-embedded cluster and thus cannot be
                 * directly locked.
                 *
                 * XXX HAMMER2 needs to implement NFS export via
                 *     mountctl.
                 */
                pmp = MPTOPMP(mp);
                pmp->hflags = info.hflags;
                cluster = &pmp->iroot->cluster;
                for (i = 0; i < cluster->nchains; ++i) {
                        if (cluster->array[i].chain == NULL)
                                continue;
                        hmp = cluster->array[i].chain->hmp;
                        devvp = hmp->devvp;
                        error = hammer2_remount(hmp, mp, path,
                                                devvp, cred);
                        if (error)
                                break;
                }

                return error;
        }

        /*
         * HMP device mount
         *
         * Lookup name and verify it refers to a block device.
         */
        if (path) {
                error = nlookup_init(&nd, dev, UIO_SYSSPACE, NLC_FOLLOW);
                if (error == 0)
                        error = nlookup(&nd);
                if (error == 0)
                        error = cache_vref(&nd.nl_nch, nd.nl_cred, &devvp);
                nlookup_done(&nd);
        } else {
                /* root mount */
                cdev_t cdev = kgetdiskbyname(dev);
                error = bdevvp(cdev, &devvp);
                if (error)
                        kprintf("hammer2: cannot find '%s'\n", dev);
        }

        if (error == 0) {
                if (vn_isdisk(devvp, &error))
                        error = vfs_mountedon(devvp);
        }

        /*
         * Determine if the device has already been mounted.  After this
         * check hmp will be non-NULL if we are doing the second or more
         * hammer2 mounts from the same device.
         */
        lockmgr(&hammer2_mntlk, LK_EXCLUSIVE);
        TAILQ_FOREACH(hmp, &hammer2_mntlist, mntentry) {
                if (hmp->devvp == devvp)
                        break;
        }

        /*
         * Open the device if this isn't a secondary mount and construct
         * the H2 device mount (hmp).
         */
        if (hmp == NULL) {
                hammer2_chain_t *schain;
                hammer2_xid_t xid;

                if (error == 0 && vcount(devvp) > 0)
                        error = EBUSY;

                /*
                 * Now open the device
                 */
                if (error == 0) {
                        ronly = ((mp->mnt_flag & MNT_RDONLY) != 0);
                        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                        error = vinvalbuf(devvp, V_SAVE, 0, 0);
                        if (error == 0) {
                                error = VOP_OPEN(devvp,
                                                 ronly ? FREAD : FREAD | FWRITE,
                                                 FSCRED, NULL);
                        }
                        vn_unlock(devvp);
                }
                if (error && devvp) {
                        vrele(devvp);
                        devvp = NULL;
                }
                if (error) {
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        return error;
                }
                hmp = kmalloc(sizeof(*hmp), M_HAMMER2, M_WAITOK | M_ZERO);
                ksnprintf(hmp->devrepname, sizeof(hmp->devrepname), "%s", dev);
                hmp->ronly = ronly;
                hmp->devvp = devvp;
                hmp->hflags = info.hflags & HMNT2_DEVFLAGS;
                kmalloc_create(&hmp->mchain, "HAMMER2-chains");
                TAILQ_INSERT_TAIL(&hammer2_mntlist, hmp, mntentry);
                RB_INIT(&hmp->iotree);
                spin_init(&hmp->io_spin, "hm2mount_io");
                spin_init(&hmp->list_spin, "hm2mount_list");
                TAILQ_INIT(&hmp->flushq);

                lockinit(&hmp->vollk, "h2vol", 0, 0);
                lockinit(&hmp->bulklk, "h2bulk", 0, 0);

                /*
                 * vchain setup. vchain.data is embedded.
                 * vchain.refs is initialized and will never drop to 0.
                 *
                 * NOTE! voldata is not yet loaded.
                 */
                hmp->vchain.hmp = hmp;
                hmp->vchain.refs = 1;
                hmp->vchain.data = (void *)&hmp->voldata;
                hmp->vchain.bref.type = HAMMER2_BREF_TYPE_VOLUME;
                hmp->vchain.bref.data_off = 0 | HAMMER2_PBUFRADIX;
                hmp->vchain.bref.mirror_tid = hmp->voldata.mirror_tid;

                hammer2_chain_core_init(&hmp->vchain);
                /* hmp->vchain.u.xxx is left NULL */

                /*
                 * fchain setup.  fchain.data is embedded.
                 * fchain.refs is initialized and will never drop to 0.
                 *
                 * The data is not used but needs to be initialized to
                 * pass assertion muster.  We use this chain primarily
                 * as a placeholder for the freemap's top-level RBTREE
                 * so it does not interfere with the volume's topology
                 * RBTREE.
                 */
                hmp->fchain.hmp = hmp;
                hmp->fchain.refs = 1;
                hmp->fchain.data = (void *)&hmp->voldata.freemap_blockset;
                hmp->fchain.bref.type = HAMMER2_BREF_TYPE_FREEMAP;
                hmp->fchain.bref.data_off = 0 | HAMMER2_PBUFRADIX;
                hmp->fchain.bref.mirror_tid = hmp->voldata.freemap_tid;
                hmp->fchain.bref.methods =
                        HAMMER2_ENC_CHECK(HAMMER2_CHECK_FREEMAP) |
                        HAMMER2_ENC_COMP(HAMMER2_COMP_NONE);

                hammer2_chain_core_init(&hmp->fchain);
                /* hmp->fchain.u.xxx is left NULL */

                /*
                 * Install the volume header and initialize fields from
                 * voldata.
                 */
                error = hammer2_install_volume_header(hmp);
                if (error) {
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return error;
                }

                /*
                 * Really important to get these right or flush will get
                 * confused.
                 */
                hmp->spmp = hammer2_pfsalloc(NULL, NULL, 0, NULL);
                kprintf("alloc spmp %p tid %016jx\n",
                        hmp->spmp, hmp->voldata.mirror_tid);
                spmp = hmp->spmp;

                /*
                 * Dummy-up vchain and fchain's modify_tid.  mirror_tid
                 * is inherited from the volume header.
                 */
                xid = 0;
                hmp->vchain.bref.mirror_tid = hmp->voldata.mirror_tid;
                hmp->vchain.bref.modify_tid = hmp->vchain.bref.mirror_tid;
                hmp->vchain.pmp = spmp;
                hmp->fchain.bref.mirror_tid = hmp->voldata.freemap_tid;
                hmp->fchain.bref.modify_tid = hmp->fchain.bref.mirror_tid;
                hmp->fchain.pmp = spmp;

                /*
                 * First locate the super-root inode, which is key 0
                 * relative to the volume header's blockset.
                 *
                 * Then locate the root inode by scanning the directory keyspace
                 * represented by the label.
                 */
                parent = hammer2_chain_lookup_init(&hmp->vchain, 0);
                schain = hammer2_chain_lookup(&parent, &key_dummy,
                                      HAMMER2_SROOT_KEY, HAMMER2_SROOT_KEY,
                                      &cache_index, 0);
                hammer2_chain_lookup_done(parent);
                if (schain == NULL) {
                        kprintf("hammer2_mount: invalid super-root\n");
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return EINVAL;
                }
                if (schain->error) {
                        kprintf("hammer2_mount: error %s reading super-root\n",
                                hammer2_error_str(schain->error));
                        hammer2_chain_unlock(schain);
                        hammer2_chain_drop(schain);
                        schain = NULL;
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return EINVAL;
                }

                /*
                 * The super-root always uses an inode_tid of 1 when
                 * creating PFSs.
                 */
                spmp->inode_tid = 1;
                spmp->modify_tid = schain->bref.modify_tid + 1;

                /*
                 * Sanity-check schain's pmp and finish initialization.
                 * Any chain belonging to the super-root topology should
                 * have a NULL pmp (not even set to spmp).
                 */
                ripdata = &hammer2_chain_rdata(schain)->ipdata;
                KKASSERT(schain->pmp == NULL);
                spmp->pfs_clid = ripdata->meta.pfs_clid;

                /*
                 * Replace the dummy spmp->iroot with a real one.  It's
                 * easier to just do a wholesale replacement than to try
                 * to update the chain and fixup the iroot fields.
                 *
                 * The returned inode is locked with the supplied cluster.
                 */
                cluster = hammer2_cluster_from_chain(schain);
                hammer2_inode_drop(spmp->iroot);
                spmp->iroot = NULL;
                spmp->iroot = hammer2_inode_get(spmp, NULL, cluster, -1);
                spmp->spmp_hmp = hmp;
                spmp->pfs_types[0] = ripdata->meta.pfs_type;
                spmp->pfs_hmps[0] = hmp;
                hammer2_inode_ref(spmp->iroot);
                hammer2_inode_unlock(spmp->iroot);
                hammer2_cluster_unlock(cluster);
                hammer2_cluster_drop(cluster);
                schain = NULL;
                /* leave spmp->iroot with one ref */

                if ((mp->mnt_flag & MNT_RDONLY) == 0) {
                        error = hammer2_recovery(hmp);
                        /* XXX do something with error */
                }
                hammer2_update_pmps(hmp);
                hammer2_iocom_init(hmp);

                /*
                 * Ref the cluster management messaging descriptor.  The mount
                 * program deals with the other end of the communications pipe.
                 *
                 * Root mounts typically do not supply one.
                 */
                if (info.cluster_fd >= 0) {
                        fp = holdfp(curproc->p_fd, info.cluster_fd, -1);
                        if (fp) {
                                hammer2_cluster_reconnect(hmp, fp);
                        } else {
                                kprintf("hammer2_mount: bad cluster_fd!\n");
                        }
                }
        } else {
                spmp = hmp->spmp;
                if (info.hflags & HMNT2_DEVFLAGS) {
                        kprintf("hammer2: Warning: mount flags pertaining "
                                "to the whole device may only be specified "
                                "on the first mount of the device: %08x\n",
                                info.hflags & HMNT2_DEVFLAGS);
                }
        }

        /*
         * Force local mount (disassociate all PFSs from their clusters).
         * Used primarily for debugging.
         */
        force_local = (hmp->hflags & HMNT2_LOCAL) ? hmp : NULL;

        /*
         * Lookup the mount point under the media-localized super-root.
         * Scanning hammer2_pfslist doesn't help us because it represents
         * PFS cluster ids which can aggregate several named PFSs together.
         *
         * cluster->pmp will incorrectly point to spmp and must be fixed
         * up later on.
         */
        hammer2_inode_lock(spmp->iroot, 0);
        parent = hammer2_inode_chain(spmp->iroot, 0, HAMMER2_RESOLVE_ALWAYS);
        lhc = hammer2_dirhash(label, strlen(label));
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                     &cache_index, 0);
        while (chain) {
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                    strcmp(label, chain->data->ipdata.filename) == 0) {
                        break;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                            key_next,
                                            lhc + HAMMER2_DIRHASH_LOMASK,
                                            &cache_index, 0);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        hammer2_inode_unlock(spmp->iroot);

        /*
         * PFS could not be found?
         */
        if (chain == NULL) {
                kprintf("hammer2_mount: PFS label not found\n");
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);

                return EINVAL;
        }

        /*
         * Acquire the pmp structure (it should have already been allocated
         * via hammer2_update_pmps() so do not pass cluster in to add to
         * available chains).
         *
         * Check if the cluster has already been mounted.  A cluster can
         * only be mounted once, use null mounts to mount additional copies.
         */
        ripdata = &chain->data->ipdata;
        bref = chain->bref;
        pmp = hammer2_pfsalloc(NULL, ripdata, bref.modify_tid, force_local);
        hammer2_chain_unlock(chain);
        hammer2_chain_drop(chain);

        if (pmp->mp) {
                kprintf("hammer2_mount: PFS already mounted!\n");
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);

                return EBUSY;
        }

        /*
         * Finish the mount
         */
        kprintf("hammer2_mount hmp=%p pmp=%p\n", hmp, pmp);

        pmp->hflags = info.hflags;
        mp->mnt_flag = MNT_LOCAL;
        mp->mnt_kern_flag |= MNTK_ALL_MPSAFE;   /* all entry pts are SMP */
        mp->mnt_kern_flag |= MNTK_THR_SYNC;     /* new vsyncscan semantics */
 
        /*
         * required mount structure initializations
         */
        mp->mnt_stat.f_iosize = HAMMER2_PBUFSIZE;
        mp->mnt_stat.f_bsize = HAMMER2_PBUFSIZE;
 
        mp->mnt_vstat.f_frsize = HAMMER2_PBUFSIZE;
        mp->mnt_vstat.f_bsize = HAMMER2_PBUFSIZE;
 
        /*
         * Optional fields
         */
        mp->mnt_iosize_max = MAXPHYS;

        /*
         * Connect up mount pointers.
         */
        hammer2_mount_helper(mp, pmp);

        lockmgr(&hammer2_mntlk, LK_RELEASE);

        /*
         * Finish setup
         */
        vfs_getnewfsid(mp);
        vfs_add_vnodeops(mp, &hammer2_vnode_vops, &mp->mnt_vn_norm_ops);
        vfs_add_vnodeops(mp, &hammer2_spec_vops, &mp->mnt_vn_spec_ops);
        vfs_add_vnodeops(mp, &hammer2_fifo_vops, &mp->mnt_vn_fifo_ops);

        if (path) {
                copyinstr(info.volume, mp->mnt_stat.f_mntfromname,
                          MNAMELEN - 1, &size);
                bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
        } /* else root mount, already in there */

        bzero(mp->mnt_stat.f_mntonname, sizeof(mp->mnt_stat.f_mntonname));
        if (path) {
                copyinstr(path, mp->mnt_stat.f_mntonname,
                          sizeof(mp->mnt_stat.f_mntonname) - 1,
                          &size);
        } else {
                /* root mount */
                mp->mnt_stat.f_mntonname[0] = '/';
        }

        /*
         * Initial statfs to prime mnt_stat.
         */
        hammer2_vfs_statfs(mp, &mp->mnt_stat, cred);
        
        return 0;
}

/*
 * Scan PFSs under the super-root and create hammer2_pfs structures.
 */
static
void
hammer2_update_pmps(hammer2_dev_t *hmp)
{
        const hammer2_inode_data_t *ripdata;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_blockref_t bref;
        hammer2_dev_t *force_local;
        hammer2_pfs_t *spmp;
        hammer2_pfs_t *pmp;
        hammer2_key_t key_next;
        int cache_index = -1;

        /*
         * Force local mount (disassociate all PFSs from their clusters).
         * Used primarily for debugging.
         */
        force_local = (hmp->hflags & HMNT2_LOCAL) ? hmp : NULL;

        /*
         * Lookup mount point under the media-localized super-root.
         *
         * cluster->pmp will incorrectly point to spmp and must be fixed
         * up later on.
         */
        spmp = hmp->spmp;
        hammer2_inode_lock(spmp->iroot, 0);
        parent = hammer2_inode_chain(spmp->iroot, 0, HAMMER2_RESOLVE_ALWAYS);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                         HAMMER2_KEY_MIN, HAMMER2_KEY_MAX,
                                         &cache_index, 0);
        while (chain) {
                if (chain->bref.type != HAMMER2_BREF_TYPE_INODE)
                        continue;
                ripdata = &chain->data->ipdata;
                bref = chain->bref;
                kprintf("ADD LOCAL PFS: %s\n", ripdata->filename);

                pmp = hammer2_pfsalloc(chain, ripdata,
                                       bref.modify_tid, force_local);
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, HAMMER2_KEY_MAX,
                                           &cache_index, 0);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        hammer2_inode_unlock(spmp->iroot);
}

static
int
hammer2_remount(hammer2_dev_t *hmp, struct mount *mp, char *path __unused,
                struct vnode *devvp, struct ucred *cred)
{
        int error;

        if (hmp->ronly && (mp->mnt_kern_flag & MNTK_WANTRDWR)) {
                error = hammer2_recovery(hmp);
        } else {
                error = 0;
        }
        return error;
}

static
int
hammer2_vfs_unmount(struct mount *mp, int mntflags)
{
        hammer2_pfs_t *pmp;
        int flags;
        int error = 0;

        pmp = MPTOPMP(mp);

        if (pmp == NULL)
                return(0);

        lockmgr(&hammer2_mntlk, LK_EXCLUSIVE);

        /*
         * If mount initialization proceeded far enough we must flush
         * its vnodes and sync the underlying mount points.  Three syncs
         * are required to fully flush the filesystem (freemap updates lag
         * by one flush, and one extra for safety).
         */
        if (mntflags & MNT_FORCE)
                flags = FORCECLOSE;
        else
                flags = 0;
        if (pmp->iroot) {
                error = vflush(mp, 0, flags);
                if (error)
                        goto failed;
                hammer2_vfs_sync(mp, MNT_WAIT);
                hammer2_vfs_sync(mp, MNT_WAIT);
                hammer2_vfs_sync(mp, MNT_WAIT);
        }

        /*
         * Cleanup the frontend support XOPS threads
         */
        hammer2_xop_helper_cleanup(pmp);

        /*
         * Cleanup our reference on ihidden.
         */
        if (pmp->ihidden) {
                hammer2_inode_drop(pmp->ihidden);
                pmp->ihidden = NULL;
        }
        if (pmp->mp)
                hammer2_unmount_helper(mp, pmp, NULL);

        error = 0;
failed:
        lockmgr(&hammer2_mntlk, LK_RELEASE);

        return (error);
}

/*
 * Mount helper, hook the system mount into our PFS.
 * The mount lock is held.
 *
 * We must bump the mount_count on related devices for any
 * mounted PFSs.
 */
static
void
hammer2_mount_helper(struct mount *mp, hammer2_pfs_t *pmp)
{
        hammer2_cluster_t *cluster;
        hammer2_chain_t *rchain;
        int i;

        mp->mnt_data = (qaddr_t)pmp;
        pmp->mp = mp;

        /*
         * After pmp->mp is set we have to adjust hmp->mount_count.
         */
        cluster = &pmp->iroot->cluster;
        for (i = 0; i < cluster->nchains; ++i) {
                rchain = cluster->array[i].chain;
                if (rchain == NULL)
                        continue;
                ++rchain->hmp->mount_count;
                kprintf("hammer2_mount hmp=%p ++mount_count=%d\n",
                        rchain->hmp, rchain->hmp->mount_count);
        }

        /*
         * Create missing Xop threads
         */
        hammer2_xop_helper_create(pmp);
}

/*
 * Mount helper, unhook the system mount from our PFS.
 * The mount lock is held.
 *
 * If hmp is supplied a mount responsible for being the first to open
 * the block device failed and the block device and all PFSs using the
 * block device must be cleaned up.
 *
 * If pmp is supplied multiple devices might be backing the PFS and each
 * must be disconnected.  This might not be the last PFS using some of the
 * underlying devices.  Also, we have to adjust our hmp->mount_count
 * accounting for the devices backing the pmp which is now undergoing an
 * unmount.
 */
static
void
hammer2_unmount_helper(struct mount *mp, hammer2_pfs_t *pmp, hammer2_dev_t *hmp)
{
        hammer2_cluster_t *cluster;
        hammer2_chain_t *rchain;
        struct vnode *devvp;
        int dumpcnt;
        int ronly = 0;
        int i;

        /*
         * If no device supplied this is a high-level unmount and we have to
         * to disconnect the mount, adjust mount_count, and locate devices
         * that might now have no mounts.
         */
        if (pmp) {
                KKASSERT(hmp == NULL);
                KKASSERT((void *)(intptr_t)mp->mnt_data == pmp);
                pmp->mp = NULL;
                mp->mnt_data = NULL;

                /*
                 * After pmp->mp is cleared we have to account for
                 * mount_count.
                 */
                cluster = &pmp->iroot->cluster;
                for (i = 0; i < cluster->nchains; ++i) {
                        rchain = cluster->array[i].chain;
                        if (rchain == NULL)
                                continue;
                        --rchain->hmp->mount_count;
                        kprintf("hammer2_unmount hmp=%p --mount_count=%d\n",
                                rchain->hmp, rchain->hmp->mount_count);
                        /* scrapping hmp now may invalidate the pmp */
                }
again:
                TAILQ_FOREACH(hmp, &hammer2_mntlist, mntentry) {
                        if (hmp->mount_count == 0) {
                                hammer2_unmount_helper(NULL, NULL, hmp);
                                goto again;
                        }
                }
                return;
        }

        /*
         * Try to terminate the block device.  We can't terminate it if
         * there are still PFSs referencing it.
         */
        kprintf("hammer2_unmount hmp=%p mount_count=%d\n",
                hmp, hmp->mount_count);
        if (hmp->mount_count)
                return;

        hammer2_pfsfree_scan(hmp);
        hammer2_dev_exlock(hmp);        /* XXX order */

        /*
         * Cycle the volume data lock as a safety (probably not needed any
         * more).  To ensure everything is out we need to flush at least
         * three times.  (1) The running of the sideq can dirty the
         * filesystem, (2) A normal flush can dirty the freemap, and
         * (3) ensure that the freemap is fully synchronized.
         *
         * The next mount's recovery scan can clean everything up but we want
         * to leave the filesystem in a 100% clean state on a normal unmount.
         */
#if 0
        hammer2_voldata_lock(hmp);
        hammer2_voldata_unlock(hmp);
#endif
        hammer2_iocom_uninit(hmp);

        if ((hmp->vchain.flags | hmp->fchain.flags) &
            HAMMER2_CHAIN_FLUSH_MASK) {
                kprintf("hammer2_unmount: chains left over "
                        "after final sync\n");
                kprintf("    vchain %08x\n", hmp->vchain.flags);
                kprintf("    fchain %08x\n", hmp->fchain.flags);

                if (hammer2_debug & 0x0010)
                        Debugger("entered debugger");
        }

        KKASSERT(hmp->spmp == NULL);

        /*
         * Finish up with the device vnode
         */
        if ((devvp = hmp->devvp) != NULL) {
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                vinvalbuf(devvp, (ronly ? 0 : V_SAVE), 0, 0);
                hmp->devvp = NULL;
                VOP_CLOSE(devvp, (ronly ? FREAD : FREAD|FWRITE), NULL);
                vn_unlock(devvp);
                vrele(devvp);
                devvp = NULL;
        }

        /*
         * Clear vchain/fchain flags that might prevent final cleanup
         * of these chains.
         */
        if (hmp->vchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_add_long(&hammer2_count_modified_chains, -1);
                atomic_clear_int(&hmp->vchain.flags, HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->vchain.pmp);
        }
        if (hmp->vchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->vchain.flags, HAMMER2_CHAIN_UPDATE);
        }

        if (hmp->fchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_add_long(&hammer2_count_modified_chains, -1);
                atomic_clear_int(&hmp->fchain.flags, HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->fchain.pmp);
        }
        if (hmp->fchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->fchain.flags, HAMMER2_CHAIN_UPDATE);
        }

        /*
         * Final drop of embedded freemap root chain to
         * clean up fchain.core (fchain structure is not
         * flagged ALLOCATED so it is cleaned out and then
         * left to rot).
         */
        hammer2_chain_drop(&hmp->fchain);

        /*
         * Final drop of embedded volume root chain to clean
         * up vchain.core (vchain structure is not flagged
         * ALLOCATED so it is cleaned out and then left to
         * rot).
         */
        dumpcnt = 50;
        hammer2_dump_chain(&hmp->vchain, 0, &dumpcnt, 'v');
        dumpcnt = 50;
        hammer2_dump_chain(&hmp->fchain, 0, &dumpcnt, 'f');
        hammer2_dev_unlock(hmp);
        hammer2_chain_drop(&hmp->vchain);

        hammer2_io_cleanup(hmp, &hmp->iotree);
        if (hmp->iofree_count) {
                kprintf("io_cleanup: %d I/O's left hanging\n",
                        hmp->iofree_count);
        }

        TAILQ_REMOVE(&hammer2_mntlist, hmp, mntentry);
        kmalloc_destroy(&hmp->mchain);
        kfree(hmp, M_HAMMER2);
}

static
int
hammer2_vfs_vget(struct mount *mp, struct vnode *dvp,
             ino_t ino, struct vnode **vpp)
{
        kprintf("hammer2_vget\n");
        return (EOPNOTSUPP);
}

static
int
hammer2_vfs_root(struct mount *mp, struct vnode **vpp)
{
        hammer2_pfs_t *pmp;
        int error;
        struct vnode *vp;

        pmp = MPTOPMP(mp);
        if (pmp->iroot == NULL) {
                *vpp = NULL;
                return EINVAL;
        }

        error = 0;
        hammer2_inode_lock(pmp->iroot, HAMMER2_RESOLVE_SHARED);

        while (pmp->inode_tid == 0) {
                hammer2_xop_ipcluster_t *xop;
                hammer2_inode_meta_t *meta;

                xop = hammer2_xop_alloc(pmp->iroot, HAMMER2_XOP_MODIFYING);
                hammer2_xop_start(&xop->head, hammer2_xop_ipcluster);
                error = hammer2_xop_collect(&xop->head, 0);

                if (error == 0) {
                        meta = &xop->head.cluster.focus->data->ipdata.meta;
                        pmp->iroot->meta = *meta;
                        pmp->inode_tid = meta->pfs_inum + 1;
                        if (pmp->inode_tid < HAMMER2_INODE_START)
                                pmp->inode_tid = HAMMER2_INODE_START;
                        pmp->modify_tid =
                                xop->head.cluster.focus->bref.modify_tid + 1;
                        kprintf("PFS: Starting inode %jd\n",
                                (intmax_t)pmp->inode_tid);
                        kprintf("PMP focus good set nextino=%ld mod=%016jx\n",
                                pmp->inode_tid, pmp->modify_tid);
                        wakeup(&pmp->iroot);

                        hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);

                        /*
                         * Prime the mount info.
                         */
                        hammer2_vfs_statfs(mp, &mp->mnt_stat, NULL);

                        /*
                         * With the cluster operational, check for and
                         * install ihidden if needed.  The install_hidden
                         * code needs to get a transaction so we must unlock
                         * iroot around it.
                         *
                         * This is only applicable PFS mounts, there is no
                         * hidden directory in the spmp.
                         */
                        hammer2_inode_unlock(pmp->iroot);
                        hammer2_inode_install_hidden(pmp);
                        hammer2_inode_lock(pmp->iroot, HAMMER2_RESOLVE_SHARED);

                        break;
                }

                /*
                 * Loop, try again
                 */
                hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);
                hammer2_inode_unlock(pmp->iroot);
                error = tsleep(&pmp->iroot, PCATCH, "h2root", hz);
                hammer2_inode_lock(pmp->iroot, HAMMER2_RESOLVE_SHARED);
                if (error == EINTR)
                        break;
        }

        if (error) {
                hammer2_inode_unlock(pmp->iroot);
                *vpp = NULL;
        } else {
                vp = hammer2_igetv(pmp->iroot, &error);
                hammer2_inode_unlock(pmp->iroot);
                *vpp = vp;
        }

        return (error);
}

/*
 * Filesystem status
 *
 * XXX incorporate ipdata->meta.inode_quota and data_quota
 */
static
int
hammer2_vfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        hammer2_blockref_t bref;
        int i;

        /*
         * NOTE: iroot might not have validated the cluster yet.
         */
        pmp = MPTOPMP(mp);

        mp->mnt_stat.f_files = 0;
        mp->mnt_stat.f_ffree = 0;
        mp->mnt_stat.f_blocks = 0;
        mp->mnt_stat.f_bfree = 0;
        mp->mnt_stat.f_bavail = 0;

        for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
                hmp = pmp->pfs_hmps[i];
                if (hmp == NULL)
                        continue;
                if (pmp->iroot->cluster.array[i].chain)
                        bref = pmp->iroot->cluster.array[i].chain->bref;
                else
                        bzero(&bref, sizeof(bref));

                mp->mnt_stat.f_files = bref.inode_count;
                mp->mnt_stat.f_ffree = 0;
                mp->mnt_stat.f_blocks = (bref.data_count +
                                         hmp->voldata.allocator_free) /
                                        mp->mnt_vstat.f_bsize;
                mp->mnt_stat.f_bfree =  hmp->voldata.allocator_free /
                                        mp->mnt_vstat.f_bsize;
                mp->mnt_stat.f_bavail = mp->mnt_stat.f_bfree;

                *sbp = mp->mnt_stat;
        }
        return (0);
}

static
int
hammer2_vfs_statvfs(struct mount *mp, struct statvfs *sbp, struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        hammer2_blockref_t bref;
        int i;

        /*
         * NOTE: iroot might not have validated the cluster yet.
         */
        pmp = MPTOPMP(mp);

        mp->mnt_vstat.f_bsize = 0;
        mp->mnt_vstat.f_files = 0;
        mp->mnt_vstat.f_ffree = 0;
        mp->mnt_vstat.f_blocks = 0;
        mp->mnt_vstat.f_bfree = 0;
        mp->mnt_vstat.f_bavail = 0;

        for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
                hmp = pmp->pfs_hmps[i];
                if (hmp == NULL)
                        continue;
                if (pmp->iroot->cluster.array[i].chain)
                        bref = pmp->iroot->cluster.array[i].chain->bref;
                else
                        bzero(&bref, sizeof(bref));

                mp->mnt_vstat.f_bsize = HAMMER2_PBUFSIZE;
                mp->mnt_vstat.f_files = bref.inode_count;
                mp->mnt_vstat.f_ffree = 0;
                mp->mnt_vstat.f_blocks = (bref.data_count +
                                         hmp->voldata.allocator_free) /
                                        mp->mnt_vstat.f_bsize;
                mp->mnt_vstat.f_bfree = hmp->voldata.allocator_free /
                                        mp->mnt_vstat.f_bsize;
                mp->mnt_vstat.f_bavail = mp->mnt_vstat.f_bfree;

                *sbp = mp->mnt_vstat;
        }
        return (0);
}

/*
 * Mount-time recovery (RW mounts)
 *
 * Updates to the free block table are allowed to lag flushes by one
 * transaction.  In case of a crash, then on a fresh mount we must do an
 * incremental scan of the last committed transaction id and make sure that
 * all related blocks have been marked allocated.
 *
 * The super-root topology and each PFS has its own transaction id domain,
 * so we must track PFS boundary transitions.
 */
struct hammer2_recovery_elm {
        TAILQ_ENTRY(hammer2_recovery_elm) entry;
        hammer2_chain_t *chain;
        hammer2_tid_t sync_tid;
};

TAILQ_HEAD(hammer2_recovery_list, hammer2_recovery_elm);

struct hammer2_recovery_info {
        struct hammer2_recovery_list list;
        hammer2_tid_t   mtid;
        int     depth;
};

static int hammer2_recovery_scan(hammer2_dev_t *hmp,
                        hammer2_chain_t *parent,
                        struct hammer2_recovery_info *info,
                        hammer2_tid_t sync_tid);

#define HAMMER2_RECOVERY_MAXDEPTH       10

static
int
hammer2_recovery(hammer2_dev_t *hmp)
{
        struct hammer2_recovery_info info;
        struct hammer2_recovery_elm *elm;
        hammer2_chain_t *parent;
        hammer2_tid_t sync_tid;
        hammer2_tid_t mirror_tid;
        int error;
        int cumulative_error = 0;

        hammer2_trans_init(hmp->spmp, 0);

        sync_tid = hmp->voldata.freemap_tid;
        mirror_tid = hmp->voldata.mirror_tid;

        kprintf("hammer2 mount \"%s\": ", hmp->devrepname);
        if (sync_tid >= mirror_tid) {
                kprintf(" no recovery needed\n");
        } else {
                kprintf(" freemap recovery %016jx-%016jx\n",
                        sync_tid + 1, mirror_tid);
        }

        TAILQ_INIT(&info.list);
        info.depth = 0;
        parent = hammer2_chain_lookup_init(&hmp->vchain, 0);
        cumulative_error = hammer2_recovery_scan(hmp, parent, &info, sync_tid);
        hammer2_chain_lookup_done(parent);

        while ((elm = TAILQ_FIRST(&info.list)) != NULL) {
                TAILQ_REMOVE(&info.list, elm, entry);
                parent = elm->chain;
                sync_tid = elm->sync_tid;
                kfree(elm, M_HAMMER2);

                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                error = hammer2_recovery_scan(hmp, parent, &info,
                                              hmp->voldata.freemap_tid);
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);     /* drop elm->chain ref */
                if (error)
                        cumulative_error = error;
        }
        hammer2_trans_done(hmp->spmp);

        return cumulative_error;
}

static
int
hammer2_recovery_scan(hammer2_dev_t *hmp, hammer2_chain_t *parent,
                      struct hammer2_recovery_info *info,
                      hammer2_tid_t sync_tid)
{
        const hammer2_inode_data_t *ripdata;
        hammer2_chain_t *chain;
        hammer2_blockref_t bref;
        int cache_index;
        int cumulative_error = 0;
        int error;
        int first;

        /*
         * Adjust freemap to ensure that the block(s) are marked allocated.
         */
        if (parent->bref.type != HAMMER2_BREF_TYPE_VOLUME) {
                hammer2_freemap_adjust(hmp, &parent->bref,
                                       HAMMER2_FREEMAP_DORECOVER);
        }

        /*
         * Check type for recursive scan
         */
        switch(parent->bref.type) {
        case HAMMER2_BREF_TYPE_VOLUME:
                /* data already instantiated */
                break;
        case HAMMER2_BREF_TYPE_INODE:
                /*
                 * Must instantiate data for DIRECTDATA test and also
                 * for recursion.
                 */
                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                ripdata = &hammer2_chain_rdata(parent)->ipdata;
                if (ripdata->meta.op_flags & HAMMER2_OPFLAG_DIRECTDATA) {
                        /* not applicable to recovery scan */
                        hammer2_chain_unlock(parent);
                        return 0;
                }
                hammer2_chain_unlock(parent);
                break;
        case HAMMER2_BREF_TYPE_INDIRECT:
                /*
                 * Must instantiate data for recursion
                 */
                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                hammer2_chain_unlock(parent);
                break;
        case HAMMER2_BREF_TYPE_DATA:
        case HAMMER2_BREF_TYPE_FREEMAP:
        case HAMMER2_BREF_TYPE_FREEMAP_NODE:
        case HAMMER2_BREF_TYPE_FREEMAP_LEAF:
                /* not applicable to recovery scan */
                return 0;
                break;
        default:
                return EDOM;
        }

        /*
         * Defer operation if depth limit reached or if we are crossing a
         * PFS boundary.
         */
        if (info->depth >= HAMMER2_RECOVERY_MAXDEPTH) {
                struct hammer2_recovery_elm *elm;

                elm = kmalloc(sizeof(*elm), M_HAMMER2, M_ZERO | M_WAITOK);
                elm->chain = parent;
                elm->sync_tid = sync_tid;
                hammer2_chain_ref(parent);
                TAILQ_INSERT_TAIL(&info->list, elm, entry);
                /* unlocked by caller */

                return(0);
        }


        /*
         * Recursive scan of the last flushed transaction only.  We are
         * doing this without pmp assignments so don't leave the chains
         * hanging around after we are done with them.
         */
        cache_index = 0;
        chain = NULL;
        first = 1;

        while (hammer2_chain_scan(parent, &chain, &bref,
                                  &first, &cache_index,
                                  HAMMER2_LOOKUP_NODATA) != NULL) {
                /*
                 * If this is a leaf
                 */
                if (chain == NULL) {
                        if (bref.mirror_tid > sync_tid) {
                                hammer2_freemap_adjust(hmp, &bref,
                                                     HAMMER2_FREEMAP_DORECOVER);
                        }
                        continue;
                }

                /*
                 * This may or may not be a recursive node.
                 */
                atomic_set_int(&chain->flags, HAMMER2_CHAIN_RELEASE);
                if (bref.mirror_tid > sync_tid) {
                        ++info->depth;
                        error = hammer2_recovery_scan(hmp, chain,
                                                      info, sync_tid);
                        --info->depth;
                        if (error)
                                cumulative_error = error;
                }

                /*
                 * Flush the recovery at the PFS boundary to stage it for
                 * the final flush of the super-root topology.
                 */
                if ((bref.flags & HAMMER2_BREF_FLAG_PFSROOT) &&
                    (chain->flags & HAMMER2_CHAIN_ONFLUSH)) {
                        hammer2_flush(chain, HAMMER2_FLUSH_TOP);
                }
        }

        return cumulative_error;
}

/*
 * Sync a mount point; this is called on a per-mount basis from the
 * filesystem syncer process periodically and whenever a user issues
 * a sync.
 */
int
hammer2_vfs_sync(struct mount *mp, int waitfor)
{
        hammer2_xop_flush_t *xop;
        struct hammer2_sync_info info;
        hammer2_inode_t *iroot;
        hammer2_pfs_t *pmp;
        int flags;
        int error;

        pmp = MPTOPMP(mp);
        iroot = pmp->iroot;
        KKASSERT(iroot);
        KKASSERT(iroot->pmp == pmp);

        /*
         * We can't acquire locks on existing vnodes while in a transaction
         * without risking a deadlock.  This assumes that vfsync() can be
         * called without the vnode locked (which it can in DragonFly).
         * Otherwise we'd have to implement a multi-pass or flag the lock
         * failures and retry.
         *
         * The reclamation code interlocks with the sync list's token
         * (by removing the vnode from the scan list) before unlocking
         * the inode, giving us time to ref the inode.
         */
        /*flags = VMSC_GETVP;*/
        flags = 0;
        if (waitfor & MNT_LAZY)
                flags |= VMSC_ONEPASS;

#if 0
        /*
         * Preflush the vnodes using a normal transaction before interlocking
         * with a flush transaction.
         */
        hammer2_trans_init(pmp, 0);
        info.error = 0;
        info.waitfor = MNT_NOWAIT;
        vsyncscan(mp, flags | VMSC_NOWAIT, hammer2_sync_scan2, &info);
        hammer2_trans_done(pmp);
#endif

        /*
         * Start our flush transaction.  This does not return until all
         * concurrent transactions have completed and will prevent any
         * new transactions from running concurrently, except for the
         * buffer cache transactions.
         *
         * For efficiency do an async pass before making sure with a
         * synchronous pass on all related buffer cache buffers.  It
         * should theoretically not be possible for any new file buffers
         * to be instantiated during this sequence.
         */
        hammer2_trans_init(pmp, HAMMER2_TRANS_ISFLUSH |
                                HAMMER2_TRANS_PREFLUSH);
        hammer2_inode_run_sideq(pmp);

        info.error = 0;
        info.waitfor = MNT_NOWAIT;
        vsyncscan(mp, flags | VMSC_NOWAIT, hammer2_sync_scan2, &info);
        info.waitfor = MNT_WAIT;
        vsyncscan(mp, flags, hammer2_sync_scan2, &info);

        /*
         * Clear PREFLUSH.  This prevents (or asserts on) any new logical
         * buffer cache flushes which occur during the flush.  Device buffers
         * are not affected.
         */
        hammer2_bioq_sync(pmp);
        hammer2_trans_clear_preflush(pmp);

        /*
         * Use the XOP interface to concurrently flush all nodes to
         * synchronize the PFSROOT subtopology to the media.  A standard
         * end-of-scan ENOENT error indicates cluster sufficiency.
         *
         * Note that this flush will not be visible on crash recovery until
         * we flush the super-root topology in the next loop.
         *
         * XXX For now wait for all flushes to complete.
         */
        if (iroot) {
                xop = hammer2_xop_alloc(iroot, HAMMER2_XOP_MODIFYING);
                hammer2_xop_start(&xop->head, hammer2_inode_xop_flush);
                error = hammer2_xop_collect(&xop->head,
                                            HAMMER2_XOP_COLLECT_WAITALL);
                hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);
                if (error == ENOENT)
                        error = 0;
        } else {
                error = 0;
        }
        hammer2_trans_done(pmp);

        return (error);
}

/*
 * Sync passes.
 *
 * Note that we ignore the tranasction mtid we got above.  Instead,
 * each vfsync below will ultimately get its own via TRANS_BUFCACHE
 * transactions.
 */
static int
hammer2_sync_scan2(struct mount *mp, struct vnode *vp, void *data)
{
        struct hammer2_sync_info *info = data;
        hammer2_inode_t *ip;
        int error;

        /*
         * Degenerate cases.  Note that ip == NULL typically means the
         * syncer vnode itself and we don't want to vclrisdirty() in that
         * situation.
         */
        ip = VTOI(vp);
        if (ip == NULL) {
                return(0);
        }
        if (vp->v_type == VNON || vp->v_type == VBAD) {
                vclrisdirty(vp);
                return(0);
        }

        /*
         * VOP_FSYNC will start a new transaction so replicate some code
         * here to do it inline (see hammer2_vop_fsync()).
         *
         * WARNING: The vfsync interacts with the buffer cache and might
         *          block, we can't hold the inode lock at that time.
         *          However, we MUST ref ip before blocking to ensure that
         *          it isn't ripped out from under us (since we do not
         *          hold a lock on the vnode).
         */
        hammer2_inode_ref(ip);
        if ((ip->flags & HAMMER2_INODE_MODIFIED) ||
            !RB_EMPTY(&vp->v_rbdirty_tree)) {
                vfsync(vp, info->waitfor, 1, NULL, NULL);
                if (ip->flags & (HAMMER2_INODE_RESIZED |
                                 HAMMER2_INODE_MODIFIED)) {
                        hammer2_inode_lock(ip, 0);
                        hammer2_inode_chain_sync(ip);
                        hammer2_inode_unlock(ip);
                }
        }
        if ((ip->flags & HAMMER2_INODE_MODIFIED) == 0 &&
            RB_EMPTY(&vp->v_rbdirty_tree)) {
                vclrisdirty(vp);
        }

        hammer2_inode_drop(ip);
#if 1
        error = 0;
        if (error)
                info->error = error;
#endif
        return(0);
}

static
int
hammer2_vfs_vptofh(struct vnode *vp, struct fid *fhp)
{
        return (0);
}

static
int
hammer2_vfs_fhtovp(struct mount *mp, struct vnode *rootvp,
               struct fid *fhp, struct vnode **vpp)
{
        return (0);
}

static
int
hammer2_vfs_checkexp(struct mount *mp, struct sockaddr *nam,
                 int *exflagsp, struct ucred **credanonp)
{
        return (0);
}

/*
 * Support code for hammer2_vfs_mount().  Read, verify, and install the volume
 * header into the HMP
 *
 * XXX read four volhdrs and use the one with the highest TID whos CRC
 *     matches.
 *
 * XXX check iCRCs.
 *
 * XXX For filesystems w/ less than 4 volhdrs, make sure to not write to
 *     nonexistant locations.
 *
 * XXX Record selected volhdr and ring updates to each of 4 volhdrs
 */
static
int
hammer2_install_volume_header(hammer2_dev_t *hmp)
{
        hammer2_volume_data_t *vd;
        struct buf *bp;
        hammer2_crc32_t crc0, crc, bcrc0, bcrc;
        int error_reported;
        int error;
        int valid;
        int i;

        error_reported = 0;
        error = 0;
        valid = 0;
        bp = NULL;

        /*
         * There are up to 4 copies of the volume header (syncs iterate
         * between them so there is no single master).  We don't trust the
         * volu_size field so we don't know precisely how large the filesystem
         * is, so depend on the OS to return an error if we go beyond the
         * block device's EOF.
         */
        for (i = 0; i < HAMMER2_NUM_VOLHDRS; i++) {
                error = bread(hmp->devvp, i * HAMMER2_ZONE_BYTES64,
                              HAMMER2_VOLUME_BYTES, &bp);
                if (error) {
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                vd = (struct hammer2_volume_data *) bp->b_data;
                if ((vd->magic != HAMMER2_VOLUME_ID_HBO) &&
                    (vd->magic != HAMMER2_VOLUME_ID_ABO)) {
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                if (vd->magic == HAMMER2_VOLUME_ID_ABO) {
                        /* XXX: Reversed-endianness filesystem */
                        kprintf("hammer2: reverse-endian filesystem detected");
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                crc = vd->icrc_sects[HAMMER2_VOL_ICRC_SECT0];
                crc0 = hammer2_icrc32(bp->b_data + HAMMER2_VOLUME_ICRC0_OFF,
                                      HAMMER2_VOLUME_ICRC0_SIZE);
                bcrc = vd->icrc_sects[HAMMER2_VOL_ICRC_SECT1];
                bcrc0 = hammer2_icrc32(bp->b_data + HAMMER2_VOLUME_ICRC1_OFF,
                                       HAMMER2_VOLUME_ICRC1_SIZE);
                if ((crc0 != crc) || (bcrc0 != bcrc)) {
                        kprintf("hammer2 volume header crc "
                                "mismatch copy #%d %08x/%08x\n",
                                i, crc0, crc);
                        error_reported = 1;
                        brelse(bp);
                        bp = NULL;
                        continue;
                }
                if (valid == 0 || hmp->voldata.mirror_tid < vd->mirror_tid) {
                        valid = 1;
                        hmp->voldata = *vd;
                        hmp->volhdrno = i;
                }
                brelse(bp);
                bp = NULL;
        }
        if (valid) {
                hmp->volsync = hmp->voldata;
                error = 0;
                if (error_reported || bootverbose || 1) { /* 1/DEBUG */
                        kprintf("hammer2: using volume header #%d\n",
                                hmp->volhdrno);
                }
        } else {
                error = EINVAL;
                kprintf("hammer2: no valid volume headers found!\n");
        }
        return (error);
}

/*
 * This handles hysteresis on regular file flushes.  Because the BIOs are
 * routed to a thread it is possible for an excessive number to build up
 * and cause long front-end stalls long before the runningbuffspace limit
 * is hit, so we implement hammer2_flush_pipe to control the
 * hysteresis.
 *
 * This is a particular problem when compression is used.
 */
void
hammer2_lwinprog_ref(hammer2_pfs_t *pmp)
{
        atomic_add_int(&pmp->count_lwinprog, 1);
}

void
hammer2_lwinprog_drop(hammer2_pfs_t *pmp)
{
        int lwinprog;

        lwinprog = atomic_fetchadd_int(&pmp->count_lwinprog, -1);
        if ((lwinprog & HAMMER2_LWINPROG_WAITING) &&
            (lwinprog & HAMMER2_LWINPROG_MASK) <= hammer2_flush_pipe * 2 / 3) {
                atomic_clear_int(&pmp->count_lwinprog,
                                 HAMMER2_LWINPROG_WAITING);
                wakeup(&pmp->count_lwinprog);
        }
        if ((lwinprog & HAMMER2_LWINPROG_WAITING0) &&
            (lwinprog & HAMMER2_LWINPROG_MASK) <= 0) {
                atomic_clear_int(&pmp->count_lwinprog,
                                 HAMMER2_LWINPROG_WAITING0);
                wakeup(&pmp->count_lwinprog);
        }
}

void
hammer2_lwinprog_wait(hammer2_pfs_t *pmp, int flush_pipe)
{
        int lwinprog;
        int lwflag = (flush_pipe) ? HAMMER2_LWINPROG_WAITING :
                                    HAMMER2_LWINPROG_WAITING0;

        for (;;) {
                lwinprog = pmp->count_lwinprog;
                cpu_ccfence();
                if ((lwinprog & HAMMER2_LWINPROG_MASK) <= flush_pipe)
                        break;
                tsleep_interlock(&pmp->count_lwinprog, 0);
                atomic_set_int(&pmp->count_lwinprog, lwflag);
                lwinprog = pmp->count_lwinprog;
                if ((lwinprog & HAMMER2_LWINPROG_MASK) <= flush_pipe)
                        break;
                tsleep(&pmp->count_lwinprog, PINTERLOCKED, "h2wpipe", hz);
        }
}

/*
 * Manage excessive memory resource use for chain and related
 * structures.
 */
void
hammer2_pfs_memory_wait(hammer2_pfs_t *pmp)
{
        uint32_t waiting;
        uint32_t count;
        uint32_t limit;
#if 0
        static int zzticks;
#endif

        /*
         * Atomic check condition and wait.  Also do an early speedup of
         * the syncer to try to avoid hitting the wait.
         */
        for (;;) {
                waiting = pmp->inmem_dirty_chains;
                cpu_ccfence();
                count = waiting & HAMMER2_DIRTYCHAIN_MASK;

                limit = pmp->mp->mnt_nvnodelistsize / 10;
                if (limit < hammer2_limit_dirty_chains)
                        limit = hammer2_limit_dirty_chains;
                if (limit < 1000)
                        limit = 1000;

#if 0
                if ((int)(ticks - zzticks) > hz) {
                        zzticks = ticks;
                        kprintf("count %ld %ld\n", count, limit);
                }
#endif

                /*
                 * Block if there are too many dirty chains present, wait
                 * for the flush to clean some out.
                 */
                if (count > limit) {
                        tsleep_interlock(&pmp->inmem_dirty_chains, 0);
                        if (atomic_cmpset_int(&pmp->inmem_dirty_chains,
                                               waiting,
                                       waiting | HAMMER2_DIRTYCHAIN_WAITING)) {
                                speedup_syncer(pmp->mp);
                                tsleep(&pmp->inmem_dirty_chains, PINTERLOCKED,
                                       "chnmem", hz);
                        }
                        continue;       /* loop on success or fail */
                }

                /*
                 * Try to start an early flush before we are forced to block.
                 */
                if (count > limit * 7 / 10)
                        speedup_syncer(pmp->mp);
                break;
        }
}

void
hammer2_pfs_memory_inc(hammer2_pfs_t *pmp)
{
        if (pmp) {
                atomic_add_int(&pmp->inmem_dirty_chains, 1);
        }
}

void
hammer2_pfs_memory_wakeup(hammer2_pfs_t *pmp)
{
        uint32_t waiting;

        if (pmp == NULL)
                return;

        for (;;) {
                waiting = pmp->inmem_dirty_chains;
                cpu_ccfence();
                if (atomic_cmpset_int(&pmp->inmem_dirty_chains,
                                       waiting,
                                       (waiting - 1) &
                                        ~HAMMER2_DIRTYCHAIN_WAITING)) {
                        break;
                }
        }

        if (waiting & HAMMER2_DIRTYCHAIN_WAITING)
                wakeup(&pmp->inmem_dirty_chains);
}

/*
 * Debugging
 */
void
hammer2_dump_chain(hammer2_chain_t *chain, int tab, int *countp, char pfx)
{
        hammer2_chain_t *scan;
        hammer2_chain_t *parent;

        --*countp;
        if (*countp == 0) {
                kprintf("%*.*s...\n", tab, tab, "");
                return;
        }
        if (*countp < 0)
                return;
        kprintf("%*.*s%c-chain %p.%d %016jx/%d mir=%016jx\n",
                tab, tab, "", pfx,
                chain, chain->bref.type,
                chain->bref.key, chain->bref.keybits,
                chain->bref.mirror_tid);

        kprintf("%*.*s      [%08x] (%s) refs=%d",
                tab, tab, "",
                chain->flags,
                ((chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                chain->data) ?  (char *)chain->data->ipdata.filename : "?"),
                chain->refs);

        parent = chain->parent;
        if (parent)
                kprintf("\n%*.*s      p=%p [pflags %08x prefs %d",
                        tab, tab, "",
                        parent, parent->flags, parent->refs);
        if (RB_EMPTY(&chain->core.rbtree)) {
                kprintf("\n");
        } else {
                kprintf(" {\n");
                RB_FOREACH(scan, hammer2_chain_tree, &chain->core.rbtree)
                        hammer2_dump_chain(scan, tab + 4, countp, 'a');
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE && chain->data)
                        kprintf("%*.*s}(%s)\n", tab, tab, "",
                                chain->data->ipdata.filename);
                else
                        kprintf("%*.*s}\n", tab, tab, "");
        }
}