[dragonfly.git] / sys / vfs / hammer / hammer_object.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.
 * 
 * $DragonFly: src/sys/vfs/hammer/hammer_object.c,v 1.97 2008/09/23 22:28:56 dillon Exp $
 */

#include "hammer.h"

static int hammer_mem_lookup(hammer_cursor_t cursor);
static void hammer_mem_first(hammer_cursor_t cursor);
static int hammer_frontend_trunc_callback(hammer_record_t record,
                                void *data __unused);
static int hammer_bulk_scan_callback(hammer_record_t record, void *data);
static int hammer_record_needs_overwrite_delete(hammer_record_t record);
static int hammer_delete_general(hammer_cursor_t cursor, hammer_inode_t ip,
                      hammer_btree_leaf_elm_t leaf);

struct rec_trunc_info {
        u_int16_t       rec_type;
        int64_t         trunc_off;
};

struct hammer_bulk_info {
        hammer_record_t record;
        struct hammer_btree_leaf_elm leaf;
};

/*
 * Red-black tree support.  Comparison code for insertion.
 */
static int
hammer_rec_rb_compare(hammer_record_t rec1, hammer_record_t rec2)
{
        if (rec1->leaf.base.rec_type < rec2->leaf.base.rec_type)
                return(-1);
        if (rec1->leaf.base.rec_type > rec2->leaf.base.rec_type)
                return(1);

        if (rec1->leaf.base.key < rec2->leaf.base.key)
                return(-1);
        if (rec1->leaf.base.key > rec2->leaf.base.key)
                return(1);

        /*
         * For search & insertion purposes records deleted by the
         * frontend or deleted/committed by the backend are silently
         * ignored.  Otherwise pipelined insertions will get messed
         * up.
         *
         * rec1 is greater then rec2 if rec1 is marked deleted.
         * rec1 is less then rec2 if rec2 is marked deleted.
         *
         * Multiple deleted records may be present, do not return 0
         * if both are marked deleted.
         */
        if (rec1->flags & (HAMMER_RECF_DELETED_FE | HAMMER_RECF_DELETED_BE |
                           HAMMER_RECF_COMMITTED)) {
                return(1);
        }
        if (rec2->flags & (HAMMER_RECF_DELETED_FE | HAMMER_RECF_DELETED_BE |
                           HAMMER_RECF_COMMITTED)) {
                return(-1);
        }

        return(0);
}

/*
 * Basic record comparison code similar to hammer_btree_cmp().
 */
static int
hammer_rec_cmp(hammer_base_elm_t elm, hammer_record_t rec)
{
        if (elm->rec_type < rec->leaf.base.rec_type)
                return(-3);
        if (elm->rec_type > rec->leaf.base.rec_type)
                return(3);

        if (elm->key < rec->leaf.base.key)
                return(-2);
        if (elm->key > rec->leaf.base.key)
                return(2);

        /*
         * Never match against an item deleted by the frontend
         * or backend, or committed by the backend.
         *
         * elm is less then rec if rec is marked deleted.
         */
        if (rec->flags & (HAMMER_RECF_DELETED_FE | HAMMER_RECF_DELETED_BE |
                          HAMMER_RECF_COMMITTED)) {
                return(-1);
        }
        return(0);
}

/*
 * Ranged scan to locate overlapping record(s).  This is used by
 * hammer_ip_get_bulk() to locate an overlapping record.  We have
 * to use a ranged scan because the keys for data records with the
 * same file base offset can be different due to differing data_len's.
 *
 * NOTE: The base file offset of a data record is (key - data_len), not (key).
 */
static int
hammer_rec_overlap_cmp(hammer_record_t rec, void *data)
{
        struct hammer_bulk_info *info = data;
        hammer_btree_leaf_elm_t leaf = &info->leaf;

        if (rec->leaf.base.rec_type < leaf->base.rec_type)
                return(-3);
        if (rec->leaf.base.rec_type > leaf->base.rec_type)
                return(3);

        /*
         * Overlap compare
         */
        if (leaf->base.rec_type == HAMMER_RECTYPE_DATA) {
                /* rec_beg >= leaf_end */
                if (rec->leaf.base.key - rec->leaf.data_len >= leaf->base.key)
                        return(2);
                /* rec_end <= leaf_beg */
                if (rec->leaf.base.key <= leaf->base.key - leaf->data_len)
                        return(-2);
        } else {
                if (rec->leaf.base.key < leaf->base.key)
                        return(-2);
                if (rec->leaf.base.key > leaf->base.key)
                        return(2);
        }

        /*
         * We have to return 0 at this point, even if DELETED_FE is set,
         * because returning anything else will cause the scan to ignore
         * one of the branches when we really want it to check both.
         */
        return(0);
}

/*
 * RB_SCAN comparison code for hammer_mem_first().  The argument order
 * is reversed so the comparison result has to be negated.  key_beg and
 * key_end are both range-inclusive.
 *
 * Localized deletions are not cached in-memory.
 */
static
int
hammer_rec_scan_cmp(hammer_record_t rec, void *data)
{
        hammer_cursor_t cursor = data;
        int r;

        r = hammer_rec_cmp(&cursor->key_beg, rec);
        if (r > 1)
                return(-1);
        r = hammer_rec_cmp(&cursor->key_end, rec);
        if (r < -1)
                return(1);
        return(0);
}

/*
 * This compare function is used when simply looking up key_beg.
 */
static
int
hammer_rec_find_cmp(hammer_record_t rec, void *data)
{
        hammer_cursor_t cursor = data;
        int r;

        r = hammer_rec_cmp(&cursor->key_beg, rec);
        if (r > 1)
                return(-1);
        if (r < -1)
                return(1);
        return(0);
}

/*
 * Locate blocks within the truncation range.  Partial blocks do not count.
 */
static
int
hammer_rec_trunc_cmp(hammer_record_t rec, void *data)
{
        struct rec_trunc_info *info = data;

        if (rec->leaf.base.rec_type < info->rec_type)
                return(-1);
        if (rec->leaf.base.rec_type > info->rec_type)
                return(1);

        switch(rec->leaf.base.rec_type) {
        case HAMMER_RECTYPE_DB:
                /*
                 * DB record key is not beyond the truncation point, retain.
                 */
                if (rec->leaf.base.key < info->trunc_off)
                        return(-1);
                break;
        case HAMMER_RECTYPE_DATA:
                /*
                 * DATA record offset start is not beyond the truncation point,
                 * retain.
                 */
                if (rec->leaf.base.key - rec->leaf.data_len < info->trunc_off)
                        return(-1);
                break;
        default:
                panic("hammer_rec_trunc_cmp: unexpected record type");
        }

        /*
         * The record start is >= the truncation point, return match,
         * the record should be destroyed.
         */
        return(0);
}

RB_GENERATE(hammer_rec_rb_tree, hammer_record, rb_node, hammer_rec_rb_compare);

/*
 * Allocate a record for the caller to finish filling in.  The record is
 * returned referenced.
 */
hammer_record_t
hammer_alloc_mem_record(hammer_inode_t ip, int data_len)
{
        hammer_record_t record;
        hammer_mount_t hmp;

        hmp = ip->hmp;
        ++hammer_count_records;
        record = kmalloc(sizeof(*record), hmp->m_misc,
                         M_WAITOK | M_ZERO | M_USE_RESERVE);
        record->flush_state = HAMMER_FST_IDLE;
        record->ip = ip;
        record->leaf.base.btype = HAMMER_BTREE_TYPE_RECORD;
        record->leaf.data_len = data_len;
        hammer_ref(&record->lock);

        if (data_len) {
                record->data = kmalloc(data_len, hmp->m_misc, M_WAITOK | M_ZERO);
                record->flags |= HAMMER_RECF_ALLOCDATA;
                ++hammer_count_record_datas;
        }

        return (record);
}

void
hammer_wait_mem_record_ident(hammer_record_t record, const char *ident)
{
        while (record->flush_state == HAMMER_FST_FLUSH) {
                record->flags |= HAMMER_RECF_WANTED;
                tsleep(record, 0, ident, 0);
        }
}

/*
 * Called from the backend, hammer_inode.c, after a record has been
 * flushed to disk.  The record has been exclusively locked by the
 * caller and interlocked with BE.
 *
 * We clean up the state, unlock, and release the record (the record
 * was referenced by the fact that it was in the HAMMER_FST_FLUSH state).
 */
void
hammer_flush_record_done(hammer_record_t record, int error)
{
        hammer_inode_t target_ip;

        KKASSERT(record->flush_state == HAMMER_FST_FLUSH);
        KKASSERT(record->flags & HAMMER_RECF_INTERLOCK_BE);

        /*
         * If an error occured, the backend was unable to sync the
         * record to its media.  Leave the record intact.
         */
        if (error) {
                hammer_critical_error(record->ip->hmp, record->ip, error,
                                      "while flushing record");
        }

        --record->flush_group->refs;
        record->flush_group = NULL;

        /*
         * Adjust the flush state and dependancy based on success or
         * failure.
         */
        if (record->flags & (HAMMER_RECF_DELETED_BE | HAMMER_RECF_COMMITTED)) {
                if ((target_ip = record->target_ip) != NULL) {
                        TAILQ_REMOVE(&target_ip->target_list, record,
                                     target_entry);
                        record->target_ip = NULL;
                        hammer_test_inode(target_ip);
                }
                record->flush_state = HAMMER_FST_IDLE;
        } else {
                if (record->target_ip) {
                        record->flush_state = HAMMER_FST_SETUP;
                        hammer_test_inode(record->ip);
                        hammer_test_inode(record->target_ip);
                } else {
                        record->flush_state = HAMMER_FST_IDLE;
                }
        }
        record->flags &= ~HAMMER_RECF_INTERLOCK_BE;

        /*
         * Cleanup
         */
        if (record->flags & HAMMER_RECF_WANTED) {
                record->flags &= ~HAMMER_RECF_WANTED;
                wakeup(record);
        }
        hammer_rel_mem_record(record);
}

/*
 * Release a memory record.  Records marked for deletion are immediately
 * removed from the RB-Tree but otherwise left intact until the last ref
 * goes away.
 */
void
hammer_rel_mem_record(struct hammer_record *record)
{
        hammer_mount_t hmp;
        hammer_reserve_t resv;
        hammer_inode_t ip;
        hammer_inode_t target_ip;

        hammer_unref(&record->lock);

        if (record->lock.refs == 0) {
                /*
                 * Upon release of the last reference wakeup any waiters.
                 * The record structure may get destroyed so callers will
                 * loop up and do a relookup.
                 *
                 * WARNING!  Record must be removed from RB-TREE before we
                 * might possibly block.  hammer_test_inode() can block!
                 */
                ip = record->ip;
                hmp = ip->hmp;

                /*
                 * Upon release of the last reference a record marked deleted
                 * by the front or backend, or committed by the backend,
                 * is destroyed.
                 */
                if (record->flags & (HAMMER_RECF_DELETED_FE |
                                     HAMMER_RECF_DELETED_BE |
                                     HAMMER_RECF_COMMITTED)) {
                        KKASSERT(ip->lock.refs > 0);
                        KKASSERT(record->flush_state != HAMMER_FST_FLUSH);

                        /*
                         * target_ip may have zero refs, we have to ref it
                         * to prevent it from being ripped out from under
                         * us.
                         */
                        if ((target_ip = record->target_ip) != NULL) {
                                TAILQ_REMOVE(&target_ip->target_list,
                                             record, target_entry);
                                record->target_ip = NULL;
                                hammer_ref(&target_ip->lock);
                        }

                        if (record->flags & HAMMER_RECF_ONRBTREE) {
                                RB_REMOVE(hammer_rec_rb_tree,
                                          &record->ip->rec_tree,
                                          record);
                                KKASSERT(ip->rsv_recs > 0);
                                --hmp->rsv_recs;
                                --ip->rsv_recs;
                                hmp->rsv_databytes -= record->leaf.data_len;
                                record->flags &= ~HAMMER_RECF_ONRBTREE;

                                if (RB_EMPTY(&record->ip->rec_tree)) {
                                        record->ip->flags &= ~HAMMER_INODE_XDIRTY;
                                        record->ip->sync_flags &= ~HAMMER_INODE_XDIRTY;
                                        hammer_test_inode(record->ip);
                                }
                        }

                        /*
                         * We must wait for any direct-IO to complete before
                         * we can destroy the record because the bio may
                         * have a reference to it.
                         */
                        if (record->flags & 
                           (HAMMER_RECF_DIRECT_IO | HAMMER_RECF_DIRECT_INVAL)) {
                                hammer_io_direct_wait(record);
                        }


                        /*
                         * Do this test after removing record from the B-Tree.
                         */
                        if (target_ip) {
                                hammer_test_inode(target_ip);
                                hammer_rel_inode(target_ip, 0);
                        }

                        if (record->flags & HAMMER_RECF_ALLOCDATA) {
                                --hammer_count_record_datas;
                                kfree(record->data, hmp->m_misc);
                                record->flags &= ~HAMMER_RECF_ALLOCDATA;
                        }

                        /*
                         * Release the reservation.
                         *
                         * If the record was not committed we can theoretically
                         * undo the reservation.  However, doing so might
                         * create weird edge cases with the ordering of
                         * direct writes because the related buffer cache
                         * elements are per-vnode.  So we don't try.
                         */
                        if ((resv = record->resv) != NULL) {
                                /* XXX undo leaf.data_offset,leaf.data_len */
                                hammer_blockmap_reserve_complete(hmp, resv);
                                record->resv = NULL;
                        }
                        record->data = NULL;
                        --hammer_count_records;
                        kfree(record, hmp->m_misc);
                }
        }
}

/*
 * Record visibility depends on whether the record is being accessed by
 * the backend or the frontend.  Backend tests ignore the frontend delete
 * flag.  Frontend tests do NOT ignore the backend delete/commit flags and
 * must also check for commit races.
 *
 * Return non-zero if the record is visible, zero if it isn't or if it is
 * deleted.  Returns 0 if the record has been comitted (unless the special
 * delete-visibility flag is set).  A committed record must be located
 * via the media B-Tree.  Returns non-zero if the record is good.
 *
 * If HAMMER_CURSOR_DELETE_VISIBILITY is set we allow deleted memory
 * records to be returned.  This is so pending deletions are detected
 * when using an iterator to locate an unused hash key, or when we need
 * to locate historical records on-disk to destroy.
 */
static __inline
int
hammer_ip_iterate_mem_good(hammer_cursor_t cursor, hammer_record_t record)
{
        if (cursor->flags & HAMMER_CURSOR_DELETE_VISIBILITY)
                return(1);
        if (cursor->flags & HAMMER_CURSOR_BACKEND) {
                if (record->flags & (HAMMER_RECF_DELETED_BE |
                                     HAMMER_RECF_COMMITTED)) {
                        return(0);
                }
        } else {
                if (record->flags & (HAMMER_RECF_DELETED_FE |
                                     HAMMER_RECF_DELETED_BE |
                                     HAMMER_RECF_COMMITTED)) {
                        return(0);
                }
        }
        return(1);
}

/*
 * This callback is used as part of the RB_SCAN function for in-memory
 * records.  We terminate it (return -1) as soon as we get a match.
 *
 * This routine is used by frontend code.
 *
 * The primary compare code does not account for ASOF lookups.  This
 * code handles that case as well as a few others.
 */
static
int
hammer_rec_scan_callback(hammer_record_t rec, void *data)
{
        hammer_cursor_t cursor = data;

        /*
         * We terminate on success, so this should be NULL on entry.
         */
        KKASSERT(cursor->iprec == NULL);

        /*
         * Skip if the record was marked deleted or committed.
         */
        if (hammer_ip_iterate_mem_good(cursor, rec) == 0)
                return(0);

        /*
         * Skip if not visible due to our as-of TID
         */
        if (cursor->flags & HAMMER_CURSOR_ASOF) {
                if (cursor->asof < rec->leaf.base.create_tid)
                        return(0);
                if (rec->leaf.base.delete_tid &&
                    cursor->asof >= rec->leaf.base.delete_tid) {
                        return(0);
                }
        }

        /*
         * ref the record.  The record is protected from backend B-Tree
         * interactions by virtue of the cursor's IP lock.
         */
        hammer_ref(&rec->lock);

        /*
         * The record may have been deleted or committed while we
         * were blocked.  XXX remove?
         */
        if (hammer_ip_iterate_mem_good(cursor, rec) == 0) {
                hammer_rel_mem_record(rec);
                return(0);
        }

        /*
         * Set the matching record and stop the scan.
         */
        cursor->iprec = rec;
        return(-1);
}


/*
 * Lookup an in-memory record given the key specified in the cursor.  Works
 * just like hammer_btree_lookup() but operates on an inode's in-memory
 * record list.
 *
 * The lookup must fail if the record is marked for deferred deletion.
 *
 * The API for mem/btree_lookup() does not mess with the ATE/EOF bits.
 */
static
int
hammer_mem_lookup(hammer_cursor_t cursor)
{
        KKASSERT(cursor->ip);
        if (cursor->iprec) {
                hammer_rel_mem_record(cursor->iprec);
                cursor->iprec = NULL;
        }
        hammer_rec_rb_tree_RB_SCAN(&cursor->ip->rec_tree, hammer_rec_find_cmp,
                                   hammer_rec_scan_callback, cursor);

        return (cursor->iprec ? 0 : ENOENT);
}

/*
 * hammer_mem_first() - locate the first in-memory record matching the
 * cursor within the bounds of the key range.
 *
 * WARNING!  API is slightly different from btree_first().  hammer_mem_first()
 * will set ATEMEM the same as MEMEOF, and does not return any error.
 */
static
void
hammer_mem_first(hammer_cursor_t cursor)
{
        hammer_inode_t ip;

        ip = cursor->ip;
        KKASSERT(ip != NULL);

        if (cursor->iprec) {
                hammer_rel_mem_record(cursor->iprec);
                cursor->iprec = NULL;
        }
        hammer_rec_rb_tree_RB_SCAN(&ip->rec_tree, hammer_rec_scan_cmp,
                                   hammer_rec_scan_callback, cursor);

        if (cursor->iprec)
                cursor->flags &= ~(HAMMER_CURSOR_MEMEOF | HAMMER_CURSOR_ATEMEM);
        else
                cursor->flags |= HAMMER_CURSOR_MEMEOF | HAMMER_CURSOR_ATEMEM;
}

/************************************************************************
 *                   HAMMER IN-MEMORY RECORD FUNCTIONS                  *
 ************************************************************************
 *
 * These functions manipulate in-memory records.  Such records typically
 * exist prior to being committed to disk or indexed via the on-disk B-Tree.
 */

/*
 * Add a directory entry (dip,ncp) which references inode (ip).
 *
 * Note that the low 32 bits of the namekey are set temporarily to create
 * a unique in-memory record, and may be modified a second time when the
 * record is synchronized to disk.  In particular, the low 32 bits cannot be
 * all 0's when synching to disk, which is not handled here.
 *
 * NOTE: bytes does not include any terminating \0 on name, and name might
 * not be terminated.
 */
int
hammer_ip_add_directory(struct hammer_transaction *trans,
                     struct hammer_inode *dip, const char *name, int bytes,
                     struct hammer_inode *ip)
{
        struct hammer_cursor cursor;
        hammer_record_t record;
        int error;
        u_int32_t max_iterations;

        record = hammer_alloc_mem_record(dip, HAMMER_ENTRY_SIZE(bytes));

        record->type = HAMMER_MEM_RECORD_ADD;
        record->leaf.base.localization = dip->obj_localization +
                                         HAMMER_LOCALIZE_MISC;
        record->leaf.base.obj_id = dip->obj_id;
        record->leaf.base.key = hammer_directory_namekey(dip, name, bytes,
                                                         &max_iterations);
        record->leaf.base.rec_type = HAMMER_RECTYPE_DIRENTRY;
        record->leaf.base.obj_type = ip->ino_leaf.base.obj_type;
        record->data->entry.obj_id = ip->obj_id;
        record->data->entry.localization = ip->obj_localization;
        bcopy(name, record->data->entry.name, bytes);

        ++ip->ino_data.nlinks;
        ip->ino_data.ctime = trans->time;
        hammer_modify_inode(ip, HAMMER_INODE_DDIRTY);

        /*
         * Find an unused namekey.  Both the in-memory record tree and
         * the B-Tree are checked.  We do not want historically deleted
         * names to create a collision as our iteration space may be limited,
         * and since create_tid wouldn't match anyway an ASOF search
         * must be used to locate collisions.
         *
         * delete-visibility is set so pending deletions do not give us
         * a false-negative on our ability to use an iterator.
         *
         * The iterator must not rollover the key.  Directory keys only
         * use the positive key space.
         */
        hammer_init_cursor(trans, &cursor, &dip->cache[1], dip);
        cursor.key_beg = record->leaf.base;
        cursor.flags |= HAMMER_CURSOR_ASOF;
        cursor.flags |= HAMMER_CURSOR_DELETE_VISIBILITY;
        cursor.asof = ip->obj_asof;

        while (hammer_ip_lookup(&cursor) == 0) {
                ++record->leaf.base.key;
                KKASSERT(record->leaf.base.key > 0);
                cursor.key_beg.key = record->leaf.base.key;
                if (--max_iterations == 0) {
                        hammer_rel_mem_record(record);
                        error = ENOSPC;
                        goto failed;
                }
        }

        /*
         * The target inode and the directory entry are bound together.
         */
        record->target_ip = ip;
        record->flush_state = HAMMER_FST_SETUP;
        TAILQ_INSERT_TAIL(&ip->target_list, record, target_entry);

        /*
         * The inode now has a dependancy and must be taken out of the idle
         * state.  An inode not in an idle state is given an extra reference.
         *
         * When transitioning to a SETUP state flag for an automatic reflush
         * when the dependancies are disposed of if someone is waiting on
         * the inode.
         */
        if (ip->flush_state == HAMMER_FST_IDLE) {
                hammer_ref(&ip->lock);
                ip->flush_state = HAMMER_FST_SETUP;
                if (ip->flags & HAMMER_INODE_FLUSHW)
                        ip->flags |= HAMMER_INODE_REFLUSH;
        }
        error = hammer_mem_add(record);
        if (error == 0) {
                dip->ino_data.mtime = trans->time;
                hammer_modify_inode(dip, HAMMER_INODE_MTIME);
        }
failed:
        hammer_done_cursor(&cursor);
        return(error);
}

/*
 * Delete the directory entry and update the inode link count.  The
 * cursor must be seeked to the directory entry record being deleted.
 *
 * The related inode should be share-locked by the caller.  The caller is
 * on the frontend.  It could also be NULL indicating that the directory
 * entry being removed has no related inode.
 *
 * This function can return EDEADLK requiring the caller to terminate
 * the cursor, any locks, wait on the returned record, and retry.
 */
int
hammer_ip_del_directory(struct hammer_transaction *trans,
                     hammer_cursor_t cursor, struct hammer_inode *dip,
                     struct hammer_inode *ip)
{
        hammer_record_t record;
        int error;

        if (hammer_cursor_inmem(cursor)) {
                /*
                 * In-memory (unsynchronized) records can simply be freed.
                 *
                 * Even though the HAMMER_RECF_DELETED_FE flag is ignored
                 * by the backend, we must still avoid races against the
                 * backend potentially syncing the record to the media.
                 *
                 * We cannot call hammer_ip_delete_record(), that routine may
                 * only be called from the backend.
                 */
                record = cursor->iprec;
                if (record->flags & (HAMMER_RECF_INTERLOCK_BE |
                                     HAMMER_RECF_DELETED_BE |
                                     HAMMER_RECF_COMMITTED)) {
                        KKASSERT(cursor->deadlk_rec == NULL);
                        hammer_ref(&record->lock);
                        cursor->deadlk_rec = record;
                        error = EDEADLK;
                } else {
                        KKASSERT(record->type == HAMMER_MEM_RECORD_ADD);
                        record->flags |= HAMMER_RECF_DELETED_FE;
                        error = 0;
                }
        } else {
                /*
                 * If the record is on-disk we have to queue the deletion by
                 * the record's key.  This also causes lookups to skip the
                 * record.
                 */
                KKASSERT(dip->flags &
                         (HAMMER_INODE_ONDISK | HAMMER_INODE_DONDISK));
                record = hammer_alloc_mem_record(dip, 0);
                record->type = HAMMER_MEM_RECORD_DEL;
                record->leaf.base = cursor->leaf->base;

                /*
                 * ip may be NULL, indicating the deletion of a directory
                 * entry which has no related inode.
                 */
                record->target_ip = ip;
                if (ip) {
                        record->flush_state = HAMMER_FST_SETUP;
                        TAILQ_INSERT_TAIL(&ip->target_list, record,
                                          target_entry);
                } else {
                        record->flush_state = HAMMER_FST_IDLE;
                }

                /*
                 * The inode now has a dependancy and must be taken out of
                 * the idle state.  An inode not in an idle state is given
                 * an extra reference.
                 *
                 * When transitioning to a SETUP state flag for an automatic
                 * reflush when the dependancies are disposed of if someone
                 * is waiting on the inode.
                 */
                if (ip && ip->flush_state == HAMMER_FST_IDLE) {
                        hammer_ref(&ip->lock);
                        ip->flush_state = HAMMER_FST_SETUP;
                        if (ip->flags & HAMMER_INODE_FLUSHW)
                                ip->flags |= HAMMER_INODE_REFLUSH;
                }

                error = hammer_mem_add(record);
        }

        /*
         * One less link.  The file may still be open in the OS even after
         * all links have gone away.
         *
         * We have to terminate the cursor before syncing the inode to
         * avoid deadlocking against ourselves.  XXX this may no longer
         * be true.
         *
         * If nlinks drops to zero and the vnode is inactive (or there is
         * no vnode), call hammer_inode_unloadable_check() to zonk the
         * inode.  If we don't do this here the inode will not be destroyed
         * on-media until we unmount.
         */
        if (error == 0) {
                if (ip) {
                        --ip->ino_data.nlinks;  /* do before we might block */
                        ip->ino_data.ctime = trans->time;
                }
                dip->ino_data.mtime = trans->time;
                hammer_modify_inode(dip, HAMMER_INODE_MTIME);
                if (ip) {
                        hammer_modify_inode(ip, HAMMER_INODE_DDIRTY);
                        if (ip->ino_data.nlinks == 0 &&
                            (ip->vp == NULL || (ip->vp->v_flag & VINACTIVE))) {
                                hammer_done_cursor(cursor);
                                hammer_inode_unloadable_check(ip, 1);
                                hammer_flush_inode(ip, 0);
                        }
                }

        }
        return(error);
}

/*
 * Add a record to an inode.
 *
 * The caller must allocate the record with hammer_alloc_mem_record(ip) and
 * initialize the following additional fields:
 *
 * The related inode should be share-locked by the caller.  The caller is
 * on the frontend.
 *
 * record->rec.entry.base.base.key
 * record->rec.entry.base.base.rec_type
 * record->rec.entry.base.base.data_len
 * record->data         (a copy will be kmalloc'd if it cannot be embedded)
 */
int
hammer_ip_add_record(struct hammer_transaction *trans, hammer_record_t record)
{
        hammer_inode_t ip = record->ip;
        int error;

        KKASSERT(record->leaf.base.localization != 0);
        record->leaf.base.obj_id = ip->obj_id;
        record->leaf.base.obj_type = ip->ino_leaf.base.obj_type;
        error = hammer_mem_add(record);
        return(error);
}

/*
 * Locate a bulk record in-memory.  Bulk records allow disk space to be
 * reserved so the front-end can flush large data writes without having
 * to queue the BIO to the flusher.  Only the related record gets queued
 * to the flusher.
 */

static hammer_record_t
hammer_ip_get_bulk(hammer_inode_t ip, off_t file_offset, int bytes)
{
        struct hammer_bulk_info info;
        
        bzero(&info, sizeof(info));
        info.leaf.base.obj_id = ip->obj_id;
        info.leaf.base.key = file_offset + bytes;
        info.leaf.base.create_tid = 0;
        info.leaf.base.delete_tid = 0;
        info.leaf.base.rec_type = HAMMER_RECTYPE_DATA;
        info.leaf.base.obj_type = 0;                            /* unused */
        info.leaf.base.btype = HAMMER_BTREE_TYPE_RECORD;        /* unused */
        info.leaf.base.localization = ip->obj_localization +    /* unused */
                                      HAMMER_LOCALIZE_MISC;
        info.leaf.data_len = bytes;

        hammer_rec_rb_tree_RB_SCAN(&ip->rec_tree, hammer_rec_overlap_cmp,
                                   hammer_bulk_scan_callback, &info);

        return(info.record);    /* may be NULL */
}

/*
 * Take records vetted by overlap_cmp.  The first non-deleted record
 * (if any) stops the scan.
 */
static int
hammer_bulk_scan_callback(hammer_record_t record, void *data)
{
        struct hammer_bulk_info *info = data;

        if (record->flags & (HAMMER_RECF_DELETED_FE | HAMMER_RECF_DELETED_BE |
                             HAMMER_RECF_COMMITTED)) {
                return(0);
        }
        hammer_ref(&record->lock);
        info->record = record;
        return(-1);                     /* stop scan */
}

/*
 * Reserve blockmap space placemarked with an in-memory record.  
 *
 * This routine is called by the frontend in order to be able to directly
 * flush a buffer cache buffer.  The frontend has locked the related buffer
 * cache buffers and we should be able to manipulate any overlapping
 * in-memory records.
 *
 * The caller is responsible for adding the returned record.
 */
hammer_record_t
hammer_ip_add_bulk(hammer_inode_t ip, off_t file_offset, void *data, int bytes,
                   int *errorp)
{
        hammer_record_t record;
        hammer_record_t conflict;
        int zone;

        /*
         * Deal with conflicting in-memory records.  We cannot have multiple
         * in-memory records for the same base offset without seriously
         * confusing the backend, including but not limited to the backend
         * issuing delete-create-delete or create-delete-create sequences
         * and asserting on the delete_tid being the same as the create_tid.
         *
         * If we encounter a record with the backend interlock set we cannot
         * immediately delete it without confusing the backend.
         */
        while ((conflict = hammer_ip_get_bulk(ip, file_offset, bytes)) !=NULL) {
                if (conflict->flags & HAMMER_RECF_INTERLOCK_BE) {
                        conflict->flags |= HAMMER_RECF_WANTED;
                        tsleep(conflict, 0, "hmrrc3", 0);
                } else {
                        conflict->flags |= HAMMER_RECF_DELETED_FE;
                }
                hammer_rel_mem_record(conflict);
        }

        /*
         * Create a record to cover the direct write.  This is called with
         * the related BIO locked so there should be no possible conflict.
         *
         * The backend is responsible for finalizing the space reserved in
         * this record.
         *
         * XXX bytes not aligned, depend on the reservation code to
         * align the reservation.
         */
        record = hammer_alloc_mem_record(ip, 0);
        zone = (bytes >= HAMMER_BUFSIZE) ? HAMMER_ZONE_LARGE_DATA_INDEX :
                                           HAMMER_ZONE_SMALL_DATA_INDEX;
        record->resv = hammer_blockmap_reserve(ip->hmp, zone, bytes,
                                               &record->leaf.data_offset,
                                               errorp);
        if (record->resv == NULL) {
                kprintf("hammer_ip_add_bulk: reservation failed\n");
                hammer_rel_mem_record(record);
                return(NULL);
        }
        record->type = HAMMER_MEM_RECORD_DATA;
        record->leaf.base.rec_type = HAMMER_RECTYPE_DATA;
        record->leaf.base.obj_type = ip->ino_leaf.base.obj_type;
        record->leaf.base.obj_id = ip->obj_id;
        record->leaf.base.key = file_offset + bytes;
        record->leaf.base.localization = ip->obj_localization +
                                         HAMMER_LOCALIZE_MISC;
        record->leaf.data_len = bytes;
        hammer_crc_set_leaf(data, &record->leaf);
        KKASSERT(*errorp == 0);
        return(record);
}

/*
 * Frontend truncation code.  Scan in-memory records only.  On-disk records
 * and records in a flushing state are handled by the backend.  The vnops
 * setattr code will handle the block containing the truncation point.
 *
 * Partial blocks are not deleted.
 */
int
hammer_ip_frontend_trunc(struct hammer_inode *ip, off_t file_size)
{
        struct rec_trunc_info info;

        switch(ip->ino_data.obj_type) {
        case HAMMER_OBJTYPE_REGFILE:
                info.rec_type = HAMMER_RECTYPE_DATA;
                break;
        case HAMMER_OBJTYPE_DBFILE:
                info.rec_type = HAMMER_RECTYPE_DB;
                break;
        default:
                return(EINVAL);
        }
        info.trunc_off = file_size;
        hammer_rec_rb_tree_RB_SCAN(&ip->rec_tree, hammer_rec_trunc_cmp,
                                   hammer_frontend_trunc_callback, &info);
        return(0);
}

static int
hammer_frontend_trunc_callback(hammer_record_t record, void *data __unused)
{
        if (record->flags & HAMMER_RECF_DELETED_FE)
                return(0);
        if (record->flush_state == HAMMER_FST_FLUSH)
                return(0);
        KKASSERT((record->flags & HAMMER_RECF_INTERLOCK_BE) == 0);
        hammer_ref(&record->lock);
        record->flags |= HAMMER_RECF_DELETED_FE;
        hammer_rel_mem_record(record);
        return(0);
}

/*
 * Return 1 if the caller must check for and delete existing records
 * before writing out a new data record.
 *
 * Return 0 if the caller can just insert the record into the B-Tree without
 * checking.
 */
static int
hammer_record_needs_overwrite_delete(hammer_record_t record)
{
        hammer_inode_t ip = record->ip;
        int64_t file_offset;
        int r;

        if (ip->ino_data.obj_type == HAMMER_OBJTYPE_DBFILE)
                file_offset = record->leaf.base.key;
        else
                file_offset = record->leaf.base.key - record->leaf.data_len;
        r = (file_offset < ip->save_trunc_off);
        if (ip->ino_data.obj_type == HAMMER_OBJTYPE_DBFILE) {
                if (ip->save_trunc_off <= record->leaf.base.key)
                        ip->save_trunc_off = record->leaf.base.key + 1;
        } else {
                if (ip->save_trunc_off < record->leaf.base.key)
                        ip->save_trunc_off = record->leaf.base.key;
        }
        return(r);
}

/*
 * Backend code.  Sync a record to the media.
 */
int
hammer_ip_sync_record_cursor(hammer_cursor_t cursor, hammer_record_t record)
{
        hammer_transaction_t trans = cursor->trans;
        int64_t file_offset;
        int bytes;
        void *bdata;
        int error;
        int doprop;

        KKASSERT(record->flush_state == HAMMER_FST_FLUSH);
        KKASSERT(record->flags & HAMMER_RECF_INTERLOCK_BE);
        KKASSERT(record->leaf.base.localization != 0);

        /*
         * Any direct-write related to the record must complete before we
         * can sync the record to the on-disk media.
         */
        if (record->flags & (HAMMER_RECF_DIRECT_IO | HAMMER_RECF_DIRECT_INVAL))
                hammer_io_direct_wait(record);

        /*
         * If this is a bulk-data record placemarker there may be an existing
         * record on-disk, indicating a data overwrite.  If there is the
         * on-disk record must be deleted before we can insert our new record.
         *
         * We've synthesized this record and do not know what the create_tid
         * on-disk is, nor how much data it represents.
         *
         * Keep in mind that (key) for data records is (base_offset + len),
         * not (base_offset).  Also, we only want to get rid of on-disk
         * records since we are trying to sync our in-memory record, call
         * hammer_ip_delete_range() with truncating set to 1 to make sure
         * it skips in-memory records.
         *
         * It is ok for the lookup to return ENOENT.
         *
         * NOTE OPTIMIZATION: sync_trunc_off is used to determine if we have
         * to call hammer_ip_delete_range() or not.  This also means we must
         * update sync_trunc_off() as we write.
         */
        if (record->type == HAMMER_MEM_RECORD_DATA &&
            hammer_record_needs_overwrite_delete(record)) {
                file_offset = record->leaf.base.key - record->leaf.data_len;
                bytes = (record->leaf.data_len + HAMMER_BUFMASK) & 
                        ~HAMMER_BUFMASK;
                KKASSERT((file_offset & HAMMER_BUFMASK) == 0);
                error = hammer_ip_delete_range(
                                cursor, record->ip,
                                file_offset, file_offset + bytes - 1,
                                1);
                if (error && error != ENOENT)
                        goto done;
        }

        /*
         * If this is a general record there may be an on-disk version
         * that must be deleted before we can insert the new record.
         */
        if (record->type == HAMMER_MEM_RECORD_GENERAL) {
                error = hammer_delete_general(cursor, record->ip,
                                              &record->leaf);
                if (error && error != ENOENT)
                        goto done;
        }

        /*
         * Setup the cursor.
         */
        hammer_normalize_cursor(cursor);
        cursor->key_beg = record->leaf.base;
        cursor->flags &= ~HAMMER_CURSOR_INITMASK;
        cursor->flags |= HAMMER_CURSOR_BACKEND;
        cursor->flags &= ~HAMMER_CURSOR_INSERT;

        /*
         * Records can wind up on-media before the inode itself is on-media.
         * Flag the case.
         */
        record->ip->flags |= HAMMER_INODE_DONDISK;

        /*
         * If we are deleting a directory entry an exact match must be
         * found on-disk.
         */
        if (record->type == HAMMER_MEM_RECORD_DEL) {
                error = hammer_btree_lookup(cursor);
                if (error == 0) {
                        KKASSERT(cursor->iprec == NULL);
                        error = hammer_ip_delete_record(cursor, record->ip,
                                                        trans->tid);
                        if (error == 0) {
                                record->flags |= HAMMER_RECF_DELETED_BE |
                                                 HAMMER_RECF_COMMITTED;
                                ++record->ip->rec_generation;
                        }
                }
                goto done;
        }

        /*
         * We are inserting.
         *
         * Issue a lookup to position the cursor and locate the insertion
         * point.  The target key should not exist.  If we are creating a
         * directory entry we may have to iterate the low 32 bits of the
         * key to find an unused key.
         */
        hammer_sync_lock_sh(trans);
        cursor->flags |= HAMMER_CURSOR_INSERT;
        error = hammer_btree_lookup(cursor);
        if (hammer_debug_inode)
                kprintf("DOINSERT LOOKUP %d\n", error);
        if (error == 0) {
                kprintf("hammer_ip_sync_record: duplicate rec "
                        "at (%016llx)\n", record->leaf.base.key);
                Debugger("duplicate record1");
                error = EIO;
        }
#if 0
        if (record->type == HAMMER_MEM_RECORD_DATA)
                kprintf("sync_record  %016llx ---------------- %016llx %d\n",
                        record->leaf.base.key - record->leaf.data_len,
                        record->leaf.data_offset, error);
#endif

        if (error != ENOENT)
                goto done_unlock;

        /*
         * Allocate the record and data.  The result buffers will be
         * marked as being modified and further calls to
         * hammer_modify_buffer() will result in unneeded UNDO records.
         *
         * Support zero-fill records (data == NULL and data_len != 0)
         */
        if (record->type == HAMMER_MEM_RECORD_DATA) {
                /*
                 * The data portion of a bulk-data record has already been
                 * committed to disk, we need only adjust the layer2
                 * statistics in the same transaction as our B-Tree insert.
                 */
                KKASSERT(record->leaf.data_offset != 0);
                error = hammer_blockmap_finalize(trans,
                                                 record->resv,
                                                 record->leaf.data_offset,
                                                 record->leaf.data_len);
        } else if (record->data && record->leaf.data_len) {
                /*
                 * Wholely cached record, with data.  Allocate the data.
                 */
                bdata = hammer_alloc_data(trans, record->leaf.data_len,
                                          record->leaf.base.rec_type,
                                          &record->leaf.data_offset,
                                          &cursor->data_buffer,
                                          0, &error);
                if (bdata == NULL)
                        goto done_unlock;
                hammer_crc_set_leaf(record->data, &record->leaf);
                hammer_modify_buffer(trans, cursor->data_buffer, NULL, 0);
                bcopy(record->data, bdata, record->leaf.data_len);
                hammer_modify_buffer_done(cursor->data_buffer);
        } else {
                /*
                 * Wholely cached record, without data.
                 */
                record->leaf.data_offset = 0;
                record->leaf.data_crc = 0;
        }

        error = hammer_btree_insert(cursor, &record->leaf, &doprop);
        if (hammer_debug_inode && error)
                kprintf("BTREE INSERT error %d @ %016llx:%d key %016llx\n", error, cursor->node->node_offset, cursor->index, record->leaf.base.key);

        /*
         * Our record is on-disk and we normally mark the in-memory version
         * as having been committed (and not BE-deleted).
         *
         * If the record represented a directory deletion but we had to
         * sync a valid directory entry to disk due to dependancies,
         * we must convert the record to a covering delete so the
         * frontend does not have visibility on the synced entry.
         */
        if (error == 0) {
                if (doprop) {
                        hammer_btree_do_propagation(cursor,
                                                    record->ip->pfsm,
                                                    &record->leaf);
                }
                if (record->flags & HAMMER_RECF_CONVERT_DELETE) {
                        /*
                         * Must convert deleted directory entry add
                         * to a directory entry delete.
                         */
                        KKASSERT(record->type == HAMMER_MEM_RECORD_ADD);
                        record->flags &= ~HAMMER_RECF_DELETED_FE;
                        record->type = HAMMER_MEM_RECORD_DEL;
                        KKASSERT(record->flush_state == HAMMER_FST_FLUSH);
                        record->flags &= ~HAMMER_RECF_CONVERT_DELETE;
                        KKASSERT((record->flags & (HAMMER_RECF_COMMITTED |
                                                 HAMMER_RECF_DELETED_BE)) == 0);
                        /* converted record is not yet committed */
                        /* hammer_flush_record_done takes care of the rest */
                } else {
                        /*
                         * Everything went fine and we are now done with
                         * this record.
                         */
                        record->flags |= HAMMER_RECF_COMMITTED;
                        ++record->ip->rec_generation;
                }
        } else {
                if (record->leaf.data_offset) {
                        hammer_blockmap_free(trans, record->leaf.data_offset,
                                             record->leaf.data_len);
                }
        }
done_unlock:
        hammer_sync_unlock(trans);
done:
        return(error);
}

/*
 * Add the record to the inode's rec_tree.  The low 32 bits of a directory
 * entry's key is used to deal with hash collisions in the upper 32 bits.
 * A unique 64 bit key is generated in-memory and may be regenerated a
 * second time when the directory record is flushed to the on-disk B-Tree.
 *
 * A referenced record is passed to this function.  This function
 * eats the reference.  If an error occurs the record will be deleted.
 *
 * A copy of the temporary record->data pointer provided by the caller
 * will be made.
 */
int
hammer_mem_add(hammer_record_t record)
{
        hammer_mount_t hmp = record->ip->hmp;

        /*
         * Make a private copy of record->data
         */
        if (record->data)
                KKASSERT(record->flags & HAMMER_RECF_ALLOCDATA);

        /*
         * Insert into the RB tree.  A unique key should have already
         * been selected if this is a directory entry.
         */
        if (RB_INSERT(hammer_rec_rb_tree, &record->ip->rec_tree, record)) {
                record->flags |= HAMMER_RECF_DELETED_FE;
                hammer_rel_mem_record(record);
                return (EEXIST);
        }
        ++hmp->count_newrecords;
        ++hmp->rsv_recs;
        ++record->ip->rsv_recs;
        record->ip->hmp->rsv_databytes += record->leaf.data_len;
        record->flags |= HAMMER_RECF_ONRBTREE;
        hammer_modify_inode(record->ip, HAMMER_INODE_XDIRTY);
        hammer_rel_mem_record(record);
        return(0);
}

/************************************************************************
 *                   HAMMER INODE MERGED-RECORD FUNCTIONS               *
 ************************************************************************
 *
 * These functions augment the B-Tree scanning functions in hammer_btree.c
 * by merging in-memory records with on-disk records.
 */

/*
 * Locate a particular record either in-memory or on-disk.
 *
 * NOTE: This is basically a standalone routine, hammer_ip_next() may
 * NOT be called to iterate results.
 */
int
hammer_ip_lookup(hammer_cursor_t cursor)
{
        int error;

        /*
         * If the element is in-memory return it without searching the
         * on-disk B-Tree
         */
        KKASSERT(cursor->ip);
        error = hammer_mem_lookup(cursor);
        if (error == 0) {
                cursor->leaf = &cursor->iprec->leaf;
                return(error);
        }
        if (error != ENOENT)
                return(error);

        /*
         * If the inode has on-disk components search the on-disk B-Tree.
         */
        if ((cursor->ip->flags & (HAMMER_INODE_ONDISK|HAMMER_INODE_DONDISK)) == 0)
                return(error);
        error = hammer_btree_lookup(cursor);
        if (error == 0)
                error = hammer_btree_extract(cursor, HAMMER_CURSOR_GET_LEAF);
        return(error);
}

/*
 * Helper for hammer_ip_first()/hammer_ip_next()
 *
 * NOTE: Both ATEDISK and DISKEOF will be set the same.  This sets up
 * hammer_ip_first() for calling hammer_ip_next(), and sets up the re-seek
 * state if hammer_ip_next() needs to re-seek.
 */
static __inline
int
_hammer_ip_seek_btree(hammer_cursor_t cursor)
{
        hammer_inode_t ip = cursor->ip;
        int error;

        if (ip->flags & (HAMMER_INODE_ONDISK|HAMMER_INODE_DONDISK)) {
                error = hammer_btree_lookup(cursor);
                if (error == ENOENT || error == EDEADLK) {
                        if (hammer_debug_general & 0x2000)
                                kprintf("error %d node %p %016llx index %d\n", error, cursor->node, cursor->node->node_offset, cursor->index);
                        cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
                        error = hammer_btree_iterate(cursor);
                }
                if (error == 0) {
                        cursor->flags &= ~(HAMMER_CURSOR_DISKEOF |
                                           HAMMER_CURSOR_ATEDISK);
                } else {
                        cursor->flags |= HAMMER_CURSOR_DISKEOF |
                                         HAMMER_CURSOR_ATEDISK;
                        if (error == ENOENT)
                                error = 0;
                }
        } else {
                cursor->flags |= HAMMER_CURSOR_DISKEOF | HAMMER_CURSOR_ATEDISK;
                error = 0;
        }
        return(error);
}

/*
 * Helper for hammer_ip_next()
 *
 * The caller has determined that the media cursor is further along than the
 * memory cursor and must be reseeked after a generation number change.
 */
static
int
_hammer_ip_reseek(hammer_cursor_t cursor)
{
        struct hammer_base_elm save;
        hammer_btree_elm_t elm;
        int error;
        int r;
        int again = 0;

        /*
         * Do the re-seek.
         */
        kprintf("HAMMER: Debug: re-seeked during scan @ino=%016llx\n",
                (long long)cursor->ip->obj_id);
        save = cursor->key_beg;
        cursor->key_beg = cursor->iprec->leaf.base;
        error = _hammer_ip_seek_btree(cursor);
        KKASSERT(error == 0);
        cursor->key_beg = save;

        /*
         * If the memory record was previous returned to
         * the caller and the media record matches
         * (-1/+1: only create_tid differs), then iterate
         * the media record to avoid a double result.
         */
        if ((cursor->flags & HAMMER_CURSOR_ATEDISK) == 0 &&
            (cursor->flags & HAMMER_CURSOR_LASTWASMEM)) {
                elm = &cursor->node->ondisk->elms[cursor->index];
                r = hammer_btree_cmp(&elm->base,
                                     &cursor->iprec->leaf.base);
                if (cursor->flags & HAMMER_CURSOR_ASOF) {
                        if (r >= -1 && r <= 1) {
                                kprintf("HAMMER: Debug: iterated after "
                                        "re-seek (asof r=%d)\n", r);
                                cursor->flags |= HAMMER_CURSOR_ATEDISK;
                                again = 1;
                        }
                } else {
                        if (r == 0) {
                                kprintf("HAMMER: Debug: iterated after "
                                        "re-seek\n");
                                cursor->flags |= HAMMER_CURSOR_ATEDISK;
                                again = 1;
                        }
                }
        }
        return(again);
}

/*
 * Locate the first record within the cursor's key_beg/key_end range,
 * restricted to a particular inode.  0 is returned on success, ENOENT
 * if no records matched the requested range, or some other error.
 *
 * When 0 is returned hammer_ip_next() may be used to iterate additional
 * records within the requested range.
 *
 * This function can return EDEADLK, requiring the caller to terminate
 * the cursor and try again.
 */

int
hammer_ip_first(hammer_cursor_t cursor)
{
        hammer_inode_t ip = cursor->ip;
        int error;

        KKASSERT(ip != NULL);

        /*
         * Clean up fields and setup for merged scan
         */
        cursor->flags &= ~HAMMER_CURSOR_RETEST;

        /*
         * Search the in-memory record list (Red-Black tree).  Unlike the
         * B-Tree search, mem_first checks for records in the range.
         *
         * This function will setup both ATEMEM and MEMEOF properly for
         * the ip iteration.  ATEMEM will be set if MEMEOF is set.
         */
        hammer_mem_first(cursor);

        /*
         * Detect generation changes during blockages, including
         * blockages which occur on the initial btree search.
         */
        cursor->rec_generation = cursor->ip->rec_generation;

        /*
         * Initial search and result
         */
        error = _hammer_ip_seek_btree(cursor);
        if (error == 0)
                error = hammer_ip_next(cursor);

        return (error);
}

/*
 * Retrieve the next record in a merged iteration within the bounds of the
 * cursor.  This call may be made multiple times after the cursor has been
 * initially searched with hammer_ip_first().
 *
 * There are numerous special cases in this code to deal with races between
 * in-memory records and on-media records.
 *
 * 0 is returned on success, ENOENT if no further records match the
 * requested range, or some other error code is returned.
 */
int
hammer_ip_next(hammer_cursor_t cursor)
{
        hammer_btree_elm_t elm;
        hammer_record_t rec;
        hammer_record_t tmprec;
        int error;
        int r;

again:
        /*
         * Get the next on-disk record
         *
         * NOTE: If we deleted the last on-disk record we had scanned
         *       ATEDISK will be clear and RETEST will be set, forcing
         *       a call to iterate.  The fact that ATEDISK is clear causes
         *       iterate to re-test the 'current' element.  If ATEDISK is
         *       set, iterate will skip the 'current' element.
         */
        error = 0;
        if ((cursor->flags & HAMMER_CURSOR_DISKEOF) == 0) {
                if (cursor->flags & (HAMMER_CURSOR_ATEDISK |
                                     HAMMER_CURSOR_RETEST)) {
                        error = hammer_btree_iterate(cursor);
                        cursor->flags &= ~HAMMER_CURSOR_RETEST;
                        if (error == 0) {
                                cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
                                hammer_cache_node(&cursor->ip->cache[1],
                                                  cursor->node);
                        } else if (error == ENOENT) {
                                cursor->flags |= HAMMER_CURSOR_DISKEOF |
                                                 HAMMER_CURSOR_ATEDISK;
                                error = 0;
                        }
                }
        }

        /*
         * If the generation changed the backend has deleted or committed
         * one or more memory records since our last check.
         *
         * When this case occurs if the disk cursor is > current memory record
         * or the disk cursor is at EOF, we must re-seek the disk-cursor.
         * Since the cursor is ahead it must have not yet been eaten (if
         * not at eof anyway). (XXX data offset case?)
         *
         * NOTE: we are not doing a full check here.  That will be handled
         * later on.
         *
         * If we have exhausted all memory records we do not have to do any
         * further seeks.
         */
        while (cursor->rec_generation != cursor->ip->rec_generation &&
               error == 0
        ) {
                kprintf("HAMMER: Debug: generation changed during scan @ino=%016llx\n", (long long)cursor->ip->obj_id);
                cursor->rec_generation = cursor->ip->rec_generation;
                if (cursor->flags & HAMMER_CURSOR_MEMEOF)
                        break;
                if (cursor->flags & HAMMER_CURSOR_DISKEOF) {
                        r = 1;
                } else {
                        KKASSERT((cursor->flags & HAMMER_CURSOR_ATEDISK) == 0);
                        elm = &cursor->node->ondisk->elms[cursor->index];
                        r = hammer_btree_cmp(&elm->base,
                                             &cursor->iprec->leaf.base);
                }

                /*
                 * Do we re-seek the media cursor?
                 */
                if (r > 0) {
                        if (_hammer_ip_reseek(cursor))
                                goto again;
                }
        }

        /*
         * We can now safely get the next in-memory record.  We cannot
         * block here.
         *
         * hammer_rec_scan_cmp:  Is the record still in our general range,
         *                       (non-inclusive of snapshot exclusions)?
         * hammer_rec_scan_callback: Is the record in our snapshot?
         */
        tmprec = NULL;
        if ((cursor->flags & HAMMER_CURSOR_MEMEOF) == 0) {
                /*
                 * If the current memory record was eaten then get the next
                 * one.  Stale records are skipped.
                 */
                if (cursor->flags & HAMMER_CURSOR_ATEMEM) {
                        tmprec = cursor->iprec;
                        cursor->iprec = NULL;
                        rec = hammer_rec_rb_tree_RB_NEXT(tmprec);
                        while (rec) {
                                if (hammer_rec_scan_cmp(rec, cursor) != 0)
                                        break;
                                if (hammer_rec_scan_callback(rec, cursor) != 0)
                                        break;
                                rec = hammer_rec_rb_tree_RB_NEXT(rec);
                        }
                        if (cursor->iprec) {
                                KKASSERT(cursor->iprec == rec);
                                cursor->flags &= ~HAMMER_CURSOR_ATEMEM;
                        } else {
                                cursor->flags |= HAMMER_CURSOR_MEMEOF;
                        }
                        cursor->flags &= ~HAMMER_CURSOR_LASTWASMEM;
                }
        }

        /*
         * MEMORY RECORD VALIDITY TEST
         *
         * (We still can't block, which is why tmprec is being held so
         * long).
         *
         * If the memory record is no longer valid we skip it.  It may
         * have been deleted by the frontend.  If it was deleted or
         * committed by the backend the generation change re-seeked the
         * disk cursor and the record will be present there.
         */
        if (error == 0 && (cursor->flags & HAMMER_CURSOR_MEMEOF) == 0) {
                KKASSERT(cursor->iprec);
                KKASSERT((cursor->flags & HAMMER_CURSOR_ATEMEM) == 0);
                if (!hammer_ip_iterate_mem_good(cursor, cursor->iprec)) {
                        cursor->flags |= HAMMER_CURSOR_ATEMEM;
                        if (tmprec)
                                hammer_rel_mem_record(tmprec);
                        goto again;
                }
        }
        if (tmprec)
                hammer_rel_mem_record(tmprec);

        /*
         * Extract either the disk or memory record depending on their
         * relative position.
         */
        error = 0;
        switch(cursor->flags & (HAMMER_CURSOR_ATEDISK | HAMMER_CURSOR_ATEMEM)) {
        case 0:
                /*
                 * Both entries valid.   Compare the entries and nominally
                 * return the first one in the sort order.  Numerous cases
                 * require special attention, however.
                 */
                elm = &cursor->node->ondisk->elms[cursor->index];
                r = hammer_btree_cmp(&elm->base, &cursor->iprec->leaf.base);

                /*
                 * If the two entries differ only by their key (-2/2) or
                 * create_tid (-1/1), and are DATA records, we may have a
                 * nominal match.  We have to calculate the base file
                 * offset of the data.
                 */
                if (r <= 2 && r >= -2 && r != 0 &&
                    cursor->ip->ino_data.obj_type == HAMMER_OBJTYPE_REGFILE &&
                    cursor->iprec->type == HAMMER_MEM_RECORD_DATA) {
                        int64_t base1 = elm->leaf.base.key - elm->leaf.data_len;
                        int64_t base2 = cursor->iprec->leaf.base.key -
                                        cursor->iprec->leaf.data_len;
                        if (base1 == base2)
                                r = 0;
                }

                if (r < 0) {
                        error = hammer_btree_extract(cursor,
                                                     HAMMER_CURSOR_GET_LEAF);
                        cursor->flags |= HAMMER_CURSOR_ATEDISK;
                        cursor->flags &= ~HAMMER_CURSOR_LASTWASMEM;
                        break;
                }

                /*
                 * If the entries match exactly the memory entry is either
                 * an on-disk directory entry deletion or a bulk data
                 * overwrite.  If it is a directory entry deletion we eat
                 * both entries.
                 *
                 * For the bulk-data overwrite case it is possible to have
                 * visibility into both, which simply means the syncer
                 * hasn't gotten around to doing the delete+insert sequence
                 * on the B-Tree.  Use the memory entry and throw away the
                 * on-disk entry.
                 *
                 * If the in-memory record is not either of these we
                 * probably caught the syncer while it was syncing it to
                 * the media.  Since we hold a shared lock on the cursor,
                 * the in-memory record had better be marked deleted at
                 * this point.
                 */
                if (r == 0) {
                        if (cursor->iprec->type == HAMMER_MEM_RECORD_DEL) {
                                if ((cursor->flags & HAMMER_CURSOR_DELETE_VISIBILITY) == 0) {
                                        cursor->flags |= HAMMER_CURSOR_ATEDISK;
                                        cursor->flags |= HAMMER_CURSOR_ATEMEM;
                                        goto again;
                                }
                        } else if (cursor->iprec->type == HAMMER_MEM_RECORD_DATA) {
                                if ((cursor->flags & HAMMER_CURSOR_DELETE_VISIBILITY) == 0) {
                                        cursor->flags |= HAMMER_CURSOR_ATEDISK;
                                }
                                /* fall through to memory entry */
                        } else {
                                panic("hammer_ip_next: duplicate mem/b-tree entry %p %d %08x", cursor->iprec, cursor->iprec->type, cursor->iprec->flags);
                                cursor->flags |= HAMMER_CURSOR_ATEMEM;
                                goto again;
                        }
                }
                /* fall through to the memory entry */
        case HAMMER_CURSOR_ATEDISK:
                /*
                 * Only the memory entry is valid.
                 */
                cursor->leaf = &cursor->iprec->leaf;
                cursor->flags |= HAMMER_CURSOR_ATEMEM;
                cursor->flags |= HAMMER_CURSOR_LASTWASMEM;

                /*
                 * If the memory entry is an on-disk deletion we should have
                 * also had found a B-Tree record.  If the backend beat us
                 * to it it would have interlocked the cursor and we should
                 * have seen the in-memory record marked DELETED_FE.
                 */
                if (cursor->iprec->type == HAMMER_MEM_RECORD_DEL &&
                    (cursor->flags & HAMMER_CURSOR_DELETE_VISIBILITY) == 0) {
                        panic("hammer_ip_next: del-on-disk with no b-tree entry iprec %p flags %08x", cursor->iprec, cursor->iprec->flags);
                }
                break;
        case HAMMER_CURSOR_ATEMEM:
                /*
                 * Only the disk entry is valid
                 */
                error = hammer_btree_extract(cursor, HAMMER_CURSOR_GET_LEAF);
                cursor->flags |= HAMMER_CURSOR_ATEDISK;
                cursor->flags &= ~HAMMER_CURSOR_LASTWASMEM;
                break;
        default:
                /*
                 * Neither entry is valid
                 *
                 * XXX error not set properly
                 */
                cursor->flags &= ~HAMMER_CURSOR_LASTWASMEM;
                cursor->leaf = NULL;
                error = ENOENT;
                break;
        }
        return(error);
}

/*
 * Resolve the cursor->data pointer for the current cursor position in
 * a merged iteration.
 */
int
hammer_ip_resolve_data(hammer_cursor_t cursor)
{
        hammer_record_t record;
        int error;

        if (hammer_cursor_inmem(cursor)) {
                /*
                 * The data associated with an in-memory record is usually
                 * kmalloced, but reserve-ahead data records will have an
                 * on-disk reference.
                 *
                 * NOTE: Reserve-ahead data records must be handled in the
                 * context of the related high level buffer cache buffer
                 * to interlock against async writes.
                 */
                record = cursor->iprec;
                cursor->data = record->data;
                error = 0;
                if (cursor->data == NULL) {
                        KKASSERT(record->leaf.base.rec_type ==
                                 HAMMER_RECTYPE_DATA);
                        cursor->data = hammer_bread_ext(cursor->trans->hmp,
                                                    record->leaf.data_offset,
                                                    record->leaf.data_len,
                                                    &error,
                                                    &cursor->data_buffer);
                }
        } else {
                cursor->leaf = &cursor->node->ondisk->elms[cursor->index].leaf;
                error = hammer_btree_extract(cursor, HAMMER_CURSOR_GET_DATA);
        }
        return(error);
}

/*
 * Backend truncation / record replacement - delete records in range.
 *
 * Delete all records within the specified range for inode ip.  In-memory
 * records still associated with the frontend are ignored. 
 *
 * If truncating is non-zero in-memory records associated with the back-end
 * are ignored.  If truncating is > 1 we can return EWOULDBLOCK.
 *
 * NOTES:
 *
 *      * An unaligned range will cause new records to be added to cover
 *        the edge cases. (XXX not implemented yet).
 *
 *      * Replacement via reservations (see hammer_ip_sync_record_cursor())
 *        also do not deal with unaligned ranges.
 *
 *      * ran_end is inclusive (e.g. 0,1023 instead of 0,1024).
 *
 *      * Record keys for regular file data have to be special-cased since
 *        they indicate the end of the range (key = base + bytes).
 *
 *      * This function may be asked to delete ridiculously huge ranges, for
 *        example if someone truncates or removes a 1TB regular file.  We
 *        must be very careful on restarts and we may have to stop w/
 *        EWOULDBLOCK to avoid blowing out the buffer cache.
 */
int
hammer_ip_delete_range(hammer_cursor_t cursor, hammer_inode_t ip,
                       int64_t ran_beg, int64_t ran_end, int truncating)
{
        hammer_transaction_t trans = cursor->trans;
        hammer_btree_leaf_elm_t leaf;
        int error;
        int64_t off;
        int64_t tmp64;

#if 0
        kprintf("delete_range %p %016llx-%016llx\n", ip, ran_beg, ran_end);
#endif

        KKASSERT(trans->type == HAMMER_TRANS_FLS);
retry:
        hammer_normalize_cursor(cursor);
        cursor->key_beg.localization = ip->obj_localization +
                                       HAMMER_LOCALIZE_MISC;
        cursor->key_beg.obj_id = ip->obj_id;
        cursor->key_beg.create_tid = 0;
        cursor->key_beg.delete_tid = 0;
        cursor->key_beg.obj_type = 0;

        if (ip->ino_data.obj_type == HAMMER_OBJTYPE_DBFILE) {
                cursor->key_beg.key = ran_beg;
                cursor->key_beg.rec_type = HAMMER_RECTYPE_DB;
        } else {
                /*
                 * The key in the B-Tree is (base+bytes), so the first possible
                 * matching key is ran_beg + 1.
                 */
                cursor->key_beg.key = ran_beg + 1;
                cursor->key_beg.rec_type = HAMMER_RECTYPE_DATA;
        }

        cursor->key_end = cursor->key_beg;
        if (ip->ino_data.obj_type == HAMMER_OBJTYPE_DBFILE) {
                cursor->key_end.key = ran_end;
        } else {
                tmp64 = ran_end + MAXPHYS + 1;  /* work around GCC-4 bug */
                if (tmp64 < ran_end)
                        cursor->key_end.key = 0x7FFFFFFFFFFFFFFFLL;
                else
                        cursor->key_end.key = ran_end + MAXPHYS + 1;
        }

        cursor->asof = ip->obj_asof;
        cursor->flags &= ~HAMMER_CURSOR_INITMASK;
        cursor->flags |= HAMMER_CURSOR_ASOF;
        cursor->flags |= HAMMER_CURSOR_DELETE_VISIBILITY;
        cursor->flags |= HAMMER_CURSOR_BACKEND;
        cursor->flags |= HAMMER_CURSOR_END_INCLUSIVE;

        error = hammer_ip_first(cursor);

        /*
         * Iterate through matching records and mark them as deleted.
         */
        while (error == 0) {
                leaf = cursor->leaf;

                KKASSERT(leaf->base.delete_tid == 0);
                KKASSERT(leaf->base.obj_id == ip->obj_id);

                /*
                 * There may be overlap cases for regular file data.  Also
                 * remember the key for a regular file record is (base + len),
                 * NOT (base).
                 *
                 * Note that do to duplicates (mem & media) allowed by
                 * DELETE_VISIBILITY, off can wind up less then ran_beg.
                 */
                if (leaf->base.rec_type == HAMMER_RECTYPE_DATA) {
                        off = leaf->base.key - leaf->data_len;
                        /*
                         * Check the left edge case.  We currently do not
                         * split existing records.
                         */
                        if (off < ran_beg && leaf->base.key > ran_beg) {
                                panic("hammer left edge case %016llx %d\n",
                                        leaf->base.key, leaf->data_len);
                        }

                        /*
                         * Check the right edge case.  Note that the
                         * record can be completely out of bounds, which
                         * terminates the search.
                         *
                         * base->key is exclusive of the right edge while
                         * ran_end is inclusive of the right edge.  The
                         * (key - data_len) left boundary is inclusive.
                         *
                         * XXX theory-check this test at some point, are
                         * we missing a + 1 somewhere?  Note that ran_end
                         * could overflow.
                         */
                        if (leaf->base.key - 1 > ran_end) {
                                if (leaf->base.key - leaf->data_len > ran_end)
                                        break;
                                panic("hammer right edge case\n");
                        }
                } else {
                        off = leaf->base.key;
                }

                /*
                 * Delete the record.  When truncating we do not delete
                 * in-memory (data) records because they represent data
                 * written after the truncation.
                 *
                 * This will also physically destroy the B-Tree entry and
                 * data if the retention policy dictates.  The function
                 * will set HAMMER_CURSOR_RETEST to cause hammer_ip_next()
                 * to retest the new 'current' element.
                 */
                if (truncating == 0 || hammer_cursor_ondisk(cursor)) {
                        error = hammer_ip_delete_record(cursor, ip, trans->tid);
                        /*
                         * If we have built up too many meta-buffers we risk
                         * deadlocking the kernel and must stop.  This can
                         * occur when deleting ridiculously huge files.
                         * sync_trunc_off is updated so the next cycle does
                         * not re-iterate records we have already deleted.
                         *
                         * This is only done with formal truncations.
                         */
                        if (truncating > 1 && error == 0 &&
                            hammer_flusher_meta_limit(ip->hmp)) {
                                ip->sync_trunc_off = off;
                                error = EWOULDBLOCK;
                        }
                }
                if (error)
                        break;
                ran_beg = off;  /* for restart */
                error = hammer_ip_next(cursor);
        }
        if (cursor->node)
                hammer_cache_node(&ip->cache[1], cursor->node);

        if (error == EDEADLK) {
                hammer_done_cursor(cursor);
                error = hammer_init_cursor(trans, cursor, &ip->cache[1], ip);
                if (error == 0)
                        goto retry;
        }
        if (error == ENOENT)
                error = 0;
        return(error);
}

/*
 * This backend function deletes the specified record on-disk, similar to
 * delete_range but for a specific record.  Unlike the exact deletions
 * used when deleting a directory entry this function uses an ASOF search 
 * like delete_range.
 *
 * This function may be called with ip->obj_asof set for a slave snapshot,
 * so don't use it.  We always delete non-historical records only.
 */
static int
hammer_delete_general(hammer_cursor_t cursor, hammer_inode_t ip,
                      hammer_btree_leaf_elm_t leaf)
{
        hammer_transaction_t trans = cursor->trans;
        int error;

        KKASSERT(trans->type == HAMMER_TRANS_FLS);
retry:
        hammer_normalize_cursor(cursor);
        cursor->key_beg = leaf->base;
        cursor->asof = HAMMER_MAX_TID;
        cursor->flags &= ~HAMMER_CURSOR_INITMASK;
        cursor->flags |= HAMMER_CURSOR_ASOF;
        cursor->flags |= HAMMER_CURSOR_BACKEND;
        cursor->flags &= ~HAMMER_CURSOR_INSERT;

        error = hammer_btree_lookup(cursor);
        if (error == 0) {
                error = hammer_ip_delete_record(cursor, ip, trans->tid);
        }
        if (error == EDEADLK) {
                hammer_done_cursor(cursor);
                error = hammer_init_cursor(trans, cursor, &ip->cache[1], ip);
                if (error == 0)
                        goto retry;
        }
        return(error);
}

/*
 * This function deletes remaining auxillary records when an inode is
 * being deleted.  This function explicitly does not delete the
 * inode record, directory entry, data, or db records.  Those must be
 * properly disposed of prior to this call.
 */
int
hammer_ip_delete_clean(hammer_cursor_t cursor, hammer_inode_t ip, int *countp)
{
        hammer_transaction_t trans = cursor->trans;
        hammer_btree_leaf_elm_t leaf;
        int error;

        KKASSERT(trans->type == HAMMER_TRANS_FLS);
retry:
        hammer_normalize_cursor(cursor);
        cursor->key_beg.localization = ip->obj_localization +
                                       HAMMER_LOCALIZE_MISC;
        cursor->key_beg.obj_id = ip->obj_id;
        cursor->key_beg.create_tid = 0;
        cursor->key_beg.delete_tid = 0;
        cursor->key_beg.obj_type = 0;
        cursor->key_beg.rec_type = HAMMER_RECTYPE_CLEAN_START;
        cursor->key_beg.key = HAMMER_MIN_KEY;

        cursor->key_end = cursor->key_beg;
        cursor->key_end.rec_type = HAMMER_RECTYPE_MAX;
        cursor->key_end.key = HAMMER_MAX_KEY;

        cursor->asof = ip->obj_asof;
        cursor->flags &= ~HAMMER_CURSOR_INITMASK;
        cursor->flags |= HAMMER_CURSOR_END_INCLUSIVE | HAMMER_CURSOR_ASOF;
        cursor->flags |= HAMMER_CURSOR_DELETE_VISIBILITY;
        cursor->flags |= HAMMER_CURSOR_BACKEND;

        error = hammer_ip_first(cursor);

        /*
         * Iterate through matching records and mark them as deleted.
         */
        while (error == 0) {
                leaf = cursor->leaf;

                KKASSERT(leaf->base.delete_tid == 0);

                /*
                 * Mark the record and B-Tree entry as deleted.  This will
                 * also physically delete the B-Tree entry, record, and
                 * data if the retention policy dictates.  The function
                 * will set HAMMER_CURSOR_RETEST to cause hammer_ip_next()
                 * to retest the new 'current' element.
                 *
                 * Directory entries (and delete-on-disk directory entries)
                 * must be synced and cannot be deleted.
                 */
                error = hammer_ip_delete_record(cursor, ip, trans->tid);
                ++*countp;
                if (error)
                        break;
                error = hammer_ip_next(cursor);
        }
        if (cursor->node)
                hammer_cache_node(&ip->cache[1], cursor->node);
        if (error == EDEADLK) {
                hammer_done_cursor(cursor);
                error = hammer_init_cursor(trans, cursor, &ip->cache[1], ip);
                if (error == 0)
                        goto retry;
        }
        if (error == ENOENT)
                error = 0;
        return(error);
}

/*
 * Delete the record at the current cursor.  On success the cursor will
 * be positioned appropriately for an iteration but may no longer be at
 * a leaf node.
 *
 * This routine is only called from the backend.
 *
 * NOTE: This can return EDEADLK, requiring the caller to terminate the
 * cursor and retry.
 */
int
hammer_ip_delete_record(hammer_cursor_t cursor, hammer_inode_t ip,
                        hammer_tid_t tid)
{
        hammer_record_t iprec;
        hammer_mount_t hmp;
        int error;

        KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
        KKASSERT(tid != 0);
        hmp = cursor->node->hmp;

        /*
         * In-memory (unsynchronized) records can simply be freed.  This
         * only occurs in range iterations since all other records are
         * individually synchronized.  Thus there should be no confusion with
         * the interlock.
         *
         * An in-memory record may be deleted before being committed to disk,
         * but could have been accessed in the mean time.  The reservation
         * code will deal with the case.
         */
        if (hammer_cursor_inmem(cursor)) {
                iprec = cursor->iprec;
                KKASSERT((iprec->flags & HAMMER_RECF_INTERLOCK_BE) ==0);
                iprec->flags |= HAMMER_RECF_DELETED_FE;
                iprec->flags |= HAMMER_RECF_DELETED_BE;
                KKASSERT(iprec->ip == ip);
                ++ip->rec_generation;
                return(0);
        }

        /*
         * On-disk records are marked as deleted by updating their delete_tid.
         * This does not effect their position in the B-Tree (which is based
         * on their create_tid).
         *
         * Frontend B-Tree operations track inodes so we tell 
         * hammer_delete_at_cursor() not to.
         */
        error = hammer_btree_extract(cursor, HAMMER_CURSOR_GET_LEAF);

        if (error == 0) {
                error = hammer_delete_at_cursor(
                                cursor,
                                HAMMER_DELETE_ADJUST | hammer_nohistory(ip),
                                cursor->trans->tid,
                                cursor->trans->time32,
                                0, NULL);
        }
        return(error);
}

/*
 * Delete the B-Tree element at the current cursor and do any necessary
 * mirror propagation.
 *
 * The cursor must be properly positioned for an iteration on return but
 * may be pointing at an internal element.
 *
 * An element can be un-deleted by passing a delete_tid of 0 with
 * HAMMER_DELETE_ADJUST.
 */
int
hammer_delete_at_cursor(hammer_cursor_t cursor, int delete_flags,
                        hammer_tid_t delete_tid, u_int32_t delete_ts,
                        int track, int64_t *stat_bytes)
{
        struct hammer_btree_leaf_elm save_leaf;
        hammer_transaction_t trans;
        hammer_btree_leaf_elm_t leaf;
        hammer_node_t node;
        hammer_btree_elm_t elm;
        hammer_off_t data_offset;
        int32_t data_len;
        u_int16_t rec_type;
        int error;
        int icount;
        int doprop;

        error = hammer_cursor_upgrade(cursor);
        if (error)
                return(error);

        trans = cursor->trans;
        node = cursor->node;
        elm = &node->ondisk->elms[cursor->index];
        leaf = &elm->leaf;
        KKASSERT(elm->base.btype == HAMMER_BTREE_TYPE_RECORD);

        hammer_sync_lock_sh(trans);
        doprop = 0;
        icount = 0;

        /*
         * Adjust the delete_tid.  Update the mirror_tid propagation field
         * as well.  delete_tid can be 0 (undelete -- used by mirroring).
         */
        if (delete_flags & HAMMER_DELETE_ADJUST) {
                if (elm->base.rec_type == HAMMER_RECTYPE_INODE) {
                        if (elm->leaf.base.delete_tid == 0 && delete_tid)
                                icount = -1;
                        if (elm->leaf.base.delete_tid && delete_tid == 0)
                                icount = 1;
                }

                hammer_modify_node(trans, node, elm, sizeof(*elm));
                elm->leaf.base.delete_tid = delete_tid;
                elm->leaf.delete_ts = delete_ts;
                hammer_modify_node_done(node);

                if (elm->leaf.base.delete_tid > node->ondisk->mirror_tid) {
                        hammer_modify_node_field(trans, node, mirror_tid);
                        node->ondisk->mirror_tid = elm->leaf.base.delete_tid;
                        hammer_modify_node_done(node);
                        doprop = 1;
                        if (hammer_debug_general & 0x0002) {
                                kprintf("delete_at_cursor: propagate %016llx"
                                        " @%016llx\n",
                                        elm->leaf.base.delete_tid,
                                        node->node_offset);
                        }
                }

                /*
                 * Adjust for the iteration.  We have deleted the current
                 * element and want to clear ATEDISK so the iteration does
                 * not skip the element after, which now becomes the current
                 * element.  This element must be re-tested if doing an
                 * iteration, which is handled by the RETEST flag.
                 */
                if ((cursor->flags & HAMMER_CURSOR_DISKEOF) == 0) {
                        cursor->flags |= HAMMER_CURSOR_RETEST;
                        cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
                }

                /*
                 * An on-disk record cannot have the same delete_tid
                 * as its create_tid.  In a chain of record updates
                 * this could result in a duplicate record.
                 */
                KKASSERT(elm->leaf.base.delete_tid !=
                         elm->leaf.base.create_tid);
        }

        /*
         * Destroy the B-Tree element if asked (typically if a nohistory
         * file or mount, or when called by the pruning code).
         *
         * Adjust the ATEDISK flag to properly support iterations.
         */
        if (delete_flags & HAMMER_DELETE_DESTROY) {
                data_offset = elm->leaf.data_offset;
                data_len = elm->leaf.data_len;
                rec_type = elm->leaf.base.rec_type;
                if (doprop) {
                        save_leaf = elm->leaf;
                        leaf = &save_leaf;
                }
                if (elm->base.rec_type == HAMMER_RECTYPE_INODE &&
                    elm->leaf.base.delete_tid == 0) {
                        icount = -1;
                }

                error = hammer_btree_delete(cursor);
                if (error == 0) {
                        /*
                         * The deletion moves the next element (if any) to
                         * the current element position.  We must clear
                         * ATEDISK so this element is not skipped and we
                         * must set RETEST to force any iteration to re-test
                         * the element.
                         */
                        if ((cursor->flags & HAMMER_CURSOR_DISKEOF) == 0) {
                                cursor->flags |= HAMMER_CURSOR_RETEST;
                                cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
                        }
                }
                if (error == 0) {
                        switch(data_offset & HAMMER_OFF_ZONE_MASK) {
                        case HAMMER_ZONE_LARGE_DATA:
                        case HAMMER_ZONE_SMALL_DATA:
                        case HAMMER_ZONE_META:
                                hammer_blockmap_free(trans,
                                                     data_offset, data_len);
                                break;
                        default:
                                break;
                        }
                }
        }

        /*
         * Track inode count and next_tid.  This is used by the mirroring
         * and PFS code.  icount can be negative, zero, or positive.
         */
        if (error == 0 && track) {
                if (icount) {
                        hammer_modify_volume_field(trans, trans->rootvol,
                                                   vol0_stat_inodes);
                        trans->rootvol->ondisk->vol0_stat_inodes += icount;
                        hammer_modify_volume_done(trans->rootvol);
                }
                if (trans->rootvol->ondisk->vol0_next_tid < delete_tid) {
                        hammer_modify_volume(trans, trans->rootvol, NULL, 0);
                        trans->rootvol->ondisk->vol0_next_tid = delete_tid;
                        hammer_modify_volume_done(trans->rootvol);
                }
        }

        /*
         * mirror_tid propagation occurs if the node's mirror_tid had to be
         * updated while adjusting the delete_tid.
         *
         * This occurs when deleting even in nohistory mode, but does not
         * occur when pruning an already-deleted node.
         *
         * cursor->ip is NULL when called from the pruning, mirroring,
         * and pfs code.  If non-NULL propagation will be conditionalized
         * on whether the PFS is in no-history mode or not.
         */
        if (doprop) {
                if (cursor->ip)
                        hammer_btree_do_propagation(cursor, cursor->ip->pfsm, leaf);
                else
                        hammer_btree_do_propagation(cursor, NULL, leaf);
        }
        hammer_sync_unlock(trans);
        return (error);
}

/*
 * Determine whether we can remove a directory.  This routine checks whether
 * a directory is empty or not and enforces flush connectivity.
 *
 * Flush connectivity requires that we block if the target directory is
 * currently flushing, otherwise it may not end up in the same flush group.
 *
 * Returns 0 on success, ENOTEMPTY or EDEADLK (or other errors) on failure.
 */
int
hammer_ip_check_directory_empty(hammer_transaction_t trans, hammer_inode_t ip)
{
        struct hammer_cursor cursor;
        int error;

        /*
         * Check directory empty
         */
        hammer_init_cursor(trans, &cursor, &ip->cache[1], ip);

        cursor.key_beg.localization = ip->obj_localization +
                                      HAMMER_LOCALIZE_MISC;
        cursor.key_beg.obj_id = ip->obj_id;
        cursor.key_beg.create_tid = 0;
        cursor.key_beg.delete_tid = 0;
        cursor.key_beg.obj_type = 0;
        cursor.key_beg.rec_type = HAMMER_RECTYPE_INODE + 1;
        cursor.key_beg.key = HAMMER_MIN_KEY;

        cursor.key_end = cursor.key_beg;
        cursor.key_end.rec_type = 0xFFFF;
        cursor.key_end.key = HAMMER_MAX_KEY;

        cursor.asof = ip->obj_asof;
        cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE | HAMMER_CURSOR_ASOF;

        error = hammer_ip_first(&cursor);
        if (error == ENOENT)
                error = 0;
        else if (error == 0)
                error = ENOTEMPTY;
        hammer_done_cursor(&cursor);
        return(error);
}