Btrfs: fix race between balance recovery and root deletion

[mirror_ubuntu-zesty-kernel.git] / fs / btrfs / delayed-ref.c

/*
 * Copyright (C) 2009 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"

struct kmem_cache *btrfs_delayed_ref_head_cachep;
struct kmem_cache *btrfs_delayed_tree_ref_cachep;
struct kmem_cache *btrfs_delayed_data_ref_cachep;
struct kmem_cache *btrfs_delayed_extent_op_cachep;
/*
 * delayed back reference update tracking.  For subvolume trees
 * we queue up extent allocations and backref maintenance for
 * delayed processing.   This avoids deep call chains where we
 * add extents in the middle of btrfs_search_slot, and it allows
 * us to buffer up frequently modified backrefs in an rb tree instead
 * of hammering updates on the extent allocation tree.
 */

/*
 * compare two delayed tree backrefs with same bytenr and type
 */
static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
                          struct btrfs_delayed_tree_ref *ref1, int type)
{
        if (type == BTRFS_TREE_BLOCK_REF_KEY) {
                if (ref1->root < ref2->root)
                        return -1;
                if (ref1->root > ref2->root)
                        return 1;
        } else {
                if (ref1->parent < ref2->parent)
                        return -1;
                if (ref1->parent > ref2->parent)
                        return 1;
        }
        return 0;
}

/*
 * compare two delayed data backrefs with same bytenr and type
 */
static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
                          struct btrfs_delayed_data_ref *ref1)
{
        if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
                if (ref1->root < ref2->root)
                        return -1;
                if (ref1->root > ref2->root)
                        return 1;
                if (ref1->objectid < ref2->objectid)
                        return -1;
                if (ref1->objectid > ref2->objectid)
                        return 1;
                if (ref1->offset < ref2->offset)
                        return -1;
                if (ref1->offset > ref2->offset)
                        return 1;
        } else {
                if (ref1->parent < ref2->parent)
                        return -1;
                if (ref1->parent > ref2->parent)
                        return 1;
        }
        return 0;
}

/*
 * entries in the rb tree are ordered by the byte number of the extent,
 * type of the delayed backrefs and content of delayed backrefs.
 */
static int comp_entry(struct btrfs_delayed_ref_node *ref2,
                      struct btrfs_delayed_ref_node *ref1,
                      bool compare_seq)
{
        if (ref1->bytenr < ref2->bytenr)
                return -1;
        if (ref1->bytenr > ref2->bytenr)
                return 1;
        if (ref1->is_head && ref2->is_head)
                return 0;
        if (ref2->is_head)
                return -1;
        if (ref1->is_head)
                return 1;
        if (ref1->type < ref2->type)
                return -1;
        if (ref1->type > ref2->type)
                return 1;
        if (ref1->no_quota > ref2->no_quota)
                return 1;
        if (ref1->no_quota < ref2->no_quota)
                return -1;
        /* merging of sequenced refs is not allowed */
        if (compare_seq) {
                if (ref1->seq < ref2->seq)
                        return -1;
                if (ref1->seq > ref2->seq)
                        return 1;
        }
        if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
            ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
                return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
                                      btrfs_delayed_node_to_tree_ref(ref1),
                                      ref1->type);
        } else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
                   ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
                return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
                                      btrfs_delayed_node_to_data_ref(ref1));
        }
        BUG();
        return 0;
}

/*
 * insert a new ref into the rbtree.  This returns any existing refs
 * for the same (bytenr,parent) tuple, or NULL if the new node was properly
 * inserted.
 */
static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
                                                  struct rb_node *node)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent_node = NULL;
        struct btrfs_delayed_ref_node *entry;
        struct btrfs_delayed_ref_node *ins;
        int cmp;

        ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
                                 rb_node);

                cmp = comp_entry(entry, ins, 1);
                if (cmp < 0)
                        p = &(*p)->rb_left;
                else if (cmp > 0)
                        p = &(*p)->rb_right;
                else
                        return entry;
        }

        rb_link_node(node, parent_node, p);
        rb_insert_color(node, root);
        return NULL;
}

/* insert a new ref to head ref rbtree */
static struct btrfs_delayed_ref_head *htree_insert(struct rb_root *root,
                                                   struct rb_node *node)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent_node = NULL;
        struct btrfs_delayed_ref_head *entry;
        struct btrfs_delayed_ref_head *ins;
        u64 bytenr;

        ins = rb_entry(node, struct btrfs_delayed_ref_head, href_node);
        bytenr = ins->node.bytenr;
        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct btrfs_delayed_ref_head,
                                 href_node);

                if (bytenr < entry->node.bytenr)
                        p = &(*p)->rb_left;
                else if (bytenr > entry->node.bytenr)
                        p = &(*p)->rb_right;
                else
                        return entry;
        }

        rb_link_node(node, parent_node, p);
        rb_insert_color(node, root);
        return NULL;
}

/*
 * find an head entry based on bytenr. This returns the delayed ref
 * head if it was able to find one, or NULL if nothing was in that spot.
 * If return_bigger is given, the next bigger entry is returned if no exact
 * match is found.
 */
static struct btrfs_delayed_ref_head *
find_ref_head(struct rb_root *root, u64 bytenr,
              int return_bigger)
{
        struct rb_node *n;
        struct btrfs_delayed_ref_head *entry;

        n = root->rb_node;
        entry = NULL;
        while (n) {
                entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);

                if (bytenr < entry->node.bytenr)
                        n = n->rb_left;
                else if (bytenr > entry->node.bytenr)
                        n = n->rb_right;
                else
                        return entry;
        }
        if (entry && return_bigger) {
                if (bytenr > entry->node.bytenr) {
                        n = rb_next(&entry->href_node);
                        if (!n)
                                n = rb_first(root);
                        entry = rb_entry(n, struct btrfs_delayed_ref_head,
                                         href_node);
                        return entry;
                }
                return entry;
        }
        return NULL;
}

int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
                           struct btrfs_delayed_ref_head *head)
{
        struct btrfs_delayed_ref_root *delayed_refs;

        delayed_refs = &trans->transaction->delayed_refs;
        assert_spin_locked(&delayed_refs->lock);
        if (mutex_trylock(&head->mutex))
                return 0;

        atomic_inc(&head->node.refs);
        spin_unlock(&delayed_refs->lock);

        mutex_lock(&head->mutex);
        spin_lock(&delayed_refs->lock);
        if (!head->node.in_tree) {
                mutex_unlock(&head->mutex);
                btrfs_put_delayed_ref(&head->node);
                return -EAGAIN;
        }
        btrfs_put_delayed_ref(&head->node);
        return 0;
}

static inline void drop_delayed_ref(struct btrfs_trans_handle *trans,
                                    struct btrfs_delayed_ref_root *delayed_refs,
                                    struct btrfs_delayed_ref_head *head,
                                    struct btrfs_delayed_ref_node *ref)
{
        if (btrfs_delayed_ref_is_head(ref)) {
                head = btrfs_delayed_node_to_head(ref);
                rb_erase(&head->href_node, &delayed_refs->href_root);
        } else {
                assert_spin_locked(&head->lock);
                rb_erase(&ref->rb_node, &head->ref_root);
        }
        ref->in_tree = 0;
        btrfs_put_delayed_ref(ref);
        atomic_dec(&delayed_refs->num_entries);
        if (trans->delayed_ref_updates)
                trans->delayed_ref_updates--;
}

static int merge_ref(struct btrfs_trans_handle *trans,
                     struct btrfs_delayed_ref_root *delayed_refs,
                     struct btrfs_delayed_ref_head *head,
                     struct btrfs_delayed_ref_node *ref, u64 seq)
{
        struct rb_node *node;
        int mod = 0;
        int done = 0;

        node = rb_next(&ref->rb_node);
        while (!done && node) {
                struct btrfs_delayed_ref_node *next;

                next = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
                node = rb_next(node);
                if (seq && next->seq >= seq)
                        break;
                if (comp_entry(ref, next, 0))
                        continue;

                if (ref->action == next->action) {
                        mod = next->ref_mod;
                } else {
                        if (ref->ref_mod < next->ref_mod) {
                                struct btrfs_delayed_ref_node *tmp;

                                tmp = ref;
                                ref = next;
                                next = tmp;
                                done = 1;
                        }
                        mod = -next->ref_mod;
                }

                drop_delayed_ref(trans, delayed_refs, head, next);
                ref->ref_mod += mod;
                if (ref->ref_mod == 0) {
                        drop_delayed_ref(trans, delayed_refs, head, ref);
                        done = 1;
                } else {
                        /*
                         * You can't have multiples of the same ref on a tree
                         * block.
                         */
                        WARN_ON(ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
                                ref->type == BTRFS_SHARED_BLOCK_REF_KEY);
                }
        }
        return done;
}

void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
                              struct btrfs_fs_info *fs_info,
                              struct btrfs_delayed_ref_root *delayed_refs,
                              struct btrfs_delayed_ref_head *head)
{
        struct rb_node *node;
        u64 seq = 0;

        assert_spin_locked(&head->lock);
        /*
         * We don't have too much refs to merge in the case of delayed data
         * refs.
         */
        if (head->is_data)
                return;

        spin_lock(&fs_info->tree_mod_seq_lock);
        if (!list_empty(&fs_info->tree_mod_seq_list)) {
                struct seq_list *elem;

                elem = list_first_entry(&fs_info->tree_mod_seq_list,
                                        struct seq_list, list);
                seq = elem->seq;
        }
        spin_unlock(&fs_info->tree_mod_seq_lock);

        node = rb_first(&head->ref_root);
        while (node) {
                struct btrfs_delayed_ref_node *ref;

                ref = rb_entry(node, struct btrfs_delayed_ref_node,
                               rb_node);
                /* We can't merge refs that are outside of our seq count */
                if (seq && ref->seq >= seq)
                        break;
                if (merge_ref(trans, delayed_refs, head, ref, seq))
                        node = rb_first(&head->ref_root);
                else
                        node = rb_next(&ref->rb_node);
        }
}

int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
                            struct btrfs_delayed_ref_root *delayed_refs,
                            u64 seq)
{
        struct seq_list *elem;
        int ret = 0;

        spin_lock(&fs_info->tree_mod_seq_lock);
        if (!list_empty(&fs_info->tree_mod_seq_list)) {
                elem = list_first_entry(&fs_info->tree_mod_seq_list,
                                        struct seq_list, list);
                if (seq >= elem->seq) {
                        pr_debug("holding back delayed_ref %#x.%x, lowest is %#x.%x (%p)\n",
                                 (u32)(seq >> 32), (u32)seq,
                                 (u32)(elem->seq >> 32), (u32)elem->seq,
                                 delayed_refs);
                        ret = 1;
                }
        }

        spin_unlock(&fs_info->tree_mod_seq_lock);
        return ret;
}

struct btrfs_delayed_ref_head *
btrfs_select_ref_head(struct btrfs_trans_handle *trans)
{
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_delayed_ref_head *head;
        u64 start;
        bool loop = false;

        delayed_refs = &trans->transaction->delayed_refs;

again:
        start = delayed_refs->run_delayed_start;
        head = find_ref_head(&delayed_refs->href_root, start, 1);
        if (!head && !loop) {
                delayed_refs->run_delayed_start = 0;
                start = 0;
                loop = true;
                head = find_ref_head(&delayed_refs->href_root, start, 1);
                if (!head)
                        return NULL;
        } else if (!head && loop) {
                return NULL;
        }

        while (head->processing) {
                struct rb_node *node;

                node = rb_next(&head->href_node);
                if (!node) {
                        if (loop)
                                return NULL;
                        delayed_refs->run_delayed_start = 0;
                        start = 0;
                        loop = true;
                        goto again;
                }
                head = rb_entry(node, struct btrfs_delayed_ref_head,
                                href_node);
        }

        head->processing = 1;
        WARN_ON(delayed_refs->num_heads_ready == 0);
        delayed_refs->num_heads_ready--;
        delayed_refs->run_delayed_start = head->node.bytenr +
                head->node.num_bytes;
        return head;
}

/*
 * helper function to update an extent delayed ref in the
 * rbtree.  existing and update must both have the same
 * bytenr and parent
 *
 * This may free existing if the update cancels out whatever
 * operation it was doing.
 */
static noinline void
update_existing_ref(struct btrfs_trans_handle *trans,
                    struct btrfs_delayed_ref_root *delayed_refs,
                    struct btrfs_delayed_ref_head *head,
                    struct btrfs_delayed_ref_node *existing,
                    struct btrfs_delayed_ref_node *update)
{
        if (update->action != existing->action) {
                /*
                 * this is effectively undoing either an add or a
                 * drop.  We decrement the ref_mod, and if it goes
                 * down to zero we just delete the entry without
                 * every changing the extent allocation tree.
                 */
                existing->ref_mod--;
                if (existing->ref_mod == 0)
                        drop_delayed_ref(trans, delayed_refs, head, existing);
                else
                        WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
                                existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
        } else {
                WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
                        existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
                /*
                 * the action on the existing ref matches
                 * the action on the ref we're trying to add.
                 * Bump the ref_mod by one so the backref that
                 * is eventually added/removed has the correct
                 * reference count
                 */
                existing->ref_mod += update->ref_mod;
        }
}

/*
 * helper function to update the accounting in the head ref
 * existing and update must have the same bytenr
 */
static noinline void
update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
                         struct btrfs_delayed_ref_node *update)
{
        struct btrfs_delayed_ref_head *existing_ref;
        struct btrfs_delayed_ref_head *ref;

        existing_ref = btrfs_delayed_node_to_head(existing);
        ref = btrfs_delayed_node_to_head(update);
        BUG_ON(existing_ref->is_data != ref->is_data);

        spin_lock(&existing_ref->lock);
        if (ref->must_insert_reserved) {
                /* if the extent was freed and then
                 * reallocated before the delayed ref
                 * entries were processed, we can end up
                 * with an existing head ref without
                 * the must_insert_reserved flag set.
                 * Set it again here
                 */
                existing_ref->must_insert_reserved = ref->must_insert_reserved;

                /*
                 * update the num_bytes so we make sure the accounting
                 * is done correctly
                 */
                existing->num_bytes = update->num_bytes;

        }

        if (ref->extent_op) {
                if (!existing_ref->extent_op) {
                        existing_ref->extent_op = ref->extent_op;
                } else {
                        if (ref->extent_op->update_key) {
                                memcpy(&existing_ref->extent_op->key,
                                       &ref->extent_op->key,
                                       sizeof(ref->extent_op->key));
                                existing_ref->extent_op->update_key = 1;
                        }
                        if (ref->extent_op->update_flags) {
                                existing_ref->extent_op->flags_to_set |=
                                        ref->extent_op->flags_to_set;
                                existing_ref->extent_op->update_flags = 1;
                        }
                        btrfs_free_delayed_extent_op(ref->extent_op);
                }
        }
        /*
         * update the reference mod on the head to reflect this new operation,
         * only need the lock for this case cause we could be processing it
         * currently, for refs we just added we know we're a-ok.
         */
        existing->ref_mod += update->ref_mod;
        spin_unlock(&existing_ref->lock);
}

/*
 * helper function to actually insert a head node into the rbtree.
 * this does all the dirty work in terms of maintaining the correct
 * overall modification count.
 */
static noinline struct btrfs_delayed_ref_head *
add_delayed_ref_head(struct btrfs_fs_info *fs_info,
                     struct btrfs_trans_handle *trans,
                     struct btrfs_delayed_ref_node *ref, u64 bytenr,
                     u64 num_bytes, int action, int is_data)
{
        struct btrfs_delayed_ref_head *existing;
        struct btrfs_delayed_ref_head *head_ref = NULL;
        struct btrfs_delayed_ref_root *delayed_refs;
        int count_mod = 1;
        int must_insert_reserved = 0;

        /*
         * the head node stores the sum of all the mods, so dropping a ref
         * should drop the sum in the head node by one.
         */
        if (action == BTRFS_UPDATE_DELAYED_HEAD)
                count_mod = 0;
        else if (action == BTRFS_DROP_DELAYED_REF)
                count_mod = -1;

        /*
         * BTRFS_ADD_DELAYED_EXTENT means that we need to update
         * the reserved accounting when the extent is finally added, or
         * if a later modification deletes the delayed ref without ever
         * inserting the extent into the extent allocation tree.
         * ref->must_insert_reserved is the flag used to record
         * that accounting mods are required.
         *
         * Once we record must_insert_reserved, switch the action to
         * BTRFS_ADD_DELAYED_REF because other special casing is not required.
         */
        if (action == BTRFS_ADD_DELAYED_EXTENT)
                must_insert_reserved = 1;
        else
                must_insert_reserved = 0;

        delayed_refs = &trans->transaction->delayed_refs;

        /* first set the basic ref node struct up */
        atomic_set(&ref->refs, 1);
        ref->bytenr = bytenr;
        ref->num_bytes = num_bytes;
        ref->ref_mod = count_mod;
        ref->type  = 0;
        ref->action  = 0;
        ref->is_head = 1;
        ref->in_tree = 1;
        ref->seq = 0;

        head_ref = btrfs_delayed_node_to_head(ref);
        head_ref->must_insert_reserved = must_insert_reserved;
        head_ref->is_data = is_data;
        head_ref->ref_root = RB_ROOT;
        head_ref->processing = 0;

        spin_lock_init(&head_ref->lock);
        mutex_init(&head_ref->mutex);

        trace_add_delayed_ref_head(ref, head_ref, action);

        existing = htree_insert(&delayed_refs->href_root,
                                &head_ref->href_node);
        if (existing) {
                update_existing_head_ref(&existing->node, ref);
                /*
                 * we've updated the existing ref, free the newly
                 * allocated ref
                 */
                kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
                head_ref = existing;
        } else {
                delayed_refs->num_heads++;
                delayed_refs->num_heads_ready++;
                atomic_inc(&delayed_refs->num_entries);
                trans->delayed_ref_updates++;
        }
        return head_ref;
}

/*
 * helper to insert a delayed tree ref into the rbtree.
 */
static noinline void
add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
                     struct btrfs_trans_handle *trans,
                     struct btrfs_delayed_ref_head *head_ref,
                     struct btrfs_delayed_ref_node *ref, u64 bytenr,
                     u64 num_bytes, u64 parent, u64 ref_root, int level,
                     int action, int no_quota)
{
        struct btrfs_delayed_ref_node *existing;
        struct btrfs_delayed_tree_ref *full_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        u64 seq = 0;

        if (action == BTRFS_ADD_DELAYED_EXTENT)
                action = BTRFS_ADD_DELAYED_REF;

        if (is_fstree(ref_root))
                seq = atomic64_read(&fs_info->tree_mod_seq);
        delayed_refs = &trans->transaction->delayed_refs;

        /* first set the basic ref node struct up */
        atomic_set(&ref->refs, 1);
        ref->bytenr = bytenr;
        ref->num_bytes = num_bytes;
        ref->ref_mod = 1;
        ref->action = action;
        ref->is_head = 0;
        ref->in_tree = 1;
        ref->no_quota = no_quota;
        ref->seq = seq;

        full_ref = btrfs_delayed_node_to_tree_ref(ref);
        full_ref->parent = parent;
        full_ref->root = ref_root;
        if (parent)
                ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
        else
                ref->type = BTRFS_TREE_BLOCK_REF_KEY;
        full_ref->level = level;

        trace_add_delayed_tree_ref(ref, full_ref, action);

        spin_lock(&head_ref->lock);
        existing = tree_insert(&head_ref->ref_root, &ref->rb_node);
        if (existing) {
                update_existing_ref(trans, delayed_refs, head_ref, existing,
                                    ref);
                /*
                 * we've updated the existing ref, free the newly
                 * allocated ref
                 */
                kmem_cache_free(btrfs_delayed_tree_ref_cachep, full_ref);
        } else {
                atomic_inc(&delayed_refs->num_entries);
                trans->delayed_ref_updates++;
        }
        spin_unlock(&head_ref->lock);
}

/*
 * helper to insert a delayed data ref into the rbtree.
 */
static noinline void
add_delayed_data_ref(struct btrfs_fs_info *fs_info,
                     struct btrfs_trans_handle *trans,
                     struct btrfs_delayed_ref_head *head_ref,
                     struct btrfs_delayed_ref_node *ref, u64 bytenr,
                     u64 num_bytes, u64 parent, u64 ref_root, u64 owner,
                     u64 offset, int action, int no_quota)
{
        struct btrfs_delayed_ref_node *existing;
        struct btrfs_delayed_data_ref *full_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        u64 seq = 0;

        if (action == BTRFS_ADD_DELAYED_EXTENT)
                action = BTRFS_ADD_DELAYED_REF;

        delayed_refs = &trans->transaction->delayed_refs;

        if (is_fstree(ref_root))
                seq = atomic64_read(&fs_info->tree_mod_seq);

        /* first set the basic ref node struct up */
        atomic_set(&ref->refs, 1);
        ref->bytenr = bytenr;
        ref->num_bytes = num_bytes;
        ref->ref_mod = 1;
        ref->action = action;
        ref->is_head = 0;
        ref->in_tree = 1;
        ref->no_quota = no_quota;
        ref->seq = seq;

        full_ref = btrfs_delayed_node_to_data_ref(ref);
        full_ref->parent = parent;
        full_ref->root = ref_root;
        if (parent)
                ref->type = BTRFS_SHARED_DATA_REF_KEY;
        else
                ref->type = BTRFS_EXTENT_DATA_REF_KEY;

        full_ref->objectid = owner;
        full_ref->offset = offset;

        trace_add_delayed_data_ref(ref, full_ref, action);

        spin_lock(&head_ref->lock);
        existing = tree_insert(&head_ref->ref_root, &ref->rb_node);
        if (existing) {
                update_existing_ref(trans, delayed_refs, head_ref, existing,
                                    ref);
                /*
                 * we've updated the existing ref, free the newly
                 * allocated ref
                 */
                kmem_cache_free(btrfs_delayed_data_ref_cachep, full_ref);
        } else {
                atomic_inc(&delayed_refs->num_entries);
                trans->delayed_ref_updates++;
        }
        spin_unlock(&head_ref->lock);
}

/*
 * add a delayed tree ref.  This does all of the accounting required
 * to make sure the delayed ref is eventually processed before this
 * transaction commits.
 */
int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
                               struct btrfs_trans_handle *trans,
                               u64 bytenr, u64 num_bytes, u64 parent,
                               u64 ref_root,  int level, int action,
                               struct btrfs_delayed_extent_op *extent_op,
                               int no_quota)
{
        struct btrfs_delayed_tree_ref *ref;
        struct btrfs_delayed_ref_head *head_ref;
        struct btrfs_delayed_ref_root *delayed_refs;

        if (!is_fstree(ref_root) || !fs_info->quota_enabled)
                no_quota = 0;

        BUG_ON(extent_op && extent_op->is_data);
        ref = kmem_cache_alloc(btrfs_delayed_tree_ref_cachep, GFP_NOFS);
        if (!ref)
                return -ENOMEM;

        head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
        if (!head_ref) {
                kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
                return -ENOMEM;
        }

        head_ref->extent_op = extent_op;

        delayed_refs = &trans->transaction->delayed_refs;
        spin_lock(&delayed_refs->lock);

        /*
         * insert both the head node and the new ref without dropping
         * the spin lock
         */
        head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node,
                                        bytenr, num_bytes, action, 0);

        add_delayed_tree_ref(fs_info, trans, head_ref, &ref->node, bytenr,
                                   num_bytes, parent, ref_root, level, action,
                                   no_quota);
        spin_unlock(&delayed_refs->lock);

        return 0;
}

/*
 * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
 */
int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
                               struct btrfs_trans_handle *trans,
                               u64 bytenr, u64 num_bytes,
                               u64 parent, u64 ref_root,
                               u64 owner, u64 offset, int action,
                               struct btrfs_delayed_extent_op *extent_op,
                               int no_quota)
{
        struct btrfs_delayed_data_ref *ref;
        struct btrfs_delayed_ref_head *head_ref;
        struct btrfs_delayed_ref_root *delayed_refs;

        if (!is_fstree(ref_root) || !fs_info->quota_enabled)
                no_quota = 0;

        BUG_ON(extent_op && !extent_op->is_data);
        ref = kmem_cache_alloc(btrfs_delayed_data_ref_cachep, GFP_NOFS);
        if (!ref)
                return -ENOMEM;

        head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
        if (!head_ref) {
                kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
                return -ENOMEM;
        }

        head_ref->extent_op = extent_op;

        delayed_refs = &trans->transaction->delayed_refs;
        spin_lock(&delayed_refs->lock);

        /*
         * insert both the head node and the new ref without dropping
         * the spin lock
         */
        head_ref = add_delayed_ref_head(fs_info, trans, &head_ref->node,
                                        bytenr, num_bytes, action, 1);

        add_delayed_data_ref(fs_info, trans, head_ref, &ref->node, bytenr,
                                   num_bytes, parent, ref_root, owner, offset,
                                   action, no_quota);
        spin_unlock(&delayed_refs->lock);

        return 0;
}

int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
                                struct btrfs_trans_handle *trans,
                                u64 bytenr, u64 num_bytes,
                                struct btrfs_delayed_extent_op *extent_op)
{
        struct btrfs_delayed_ref_head *head_ref;
        struct btrfs_delayed_ref_root *delayed_refs;

        head_ref = kmem_cache_alloc(btrfs_delayed_ref_head_cachep, GFP_NOFS);
        if (!head_ref)
                return -ENOMEM;

        head_ref->extent_op = extent_op;

        delayed_refs = &trans->transaction->delayed_refs;
        spin_lock(&delayed_refs->lock);

        add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
                                   num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
                                   extent_op->is_data);

        spin_unlock(&delayed_refs->lock);
        return 0;
}

/*
 * this does a simple search for the head node for a given extent.
 * It must be called with the delayed ref spinlock held, and it returns
 * the head node if any where found, or NULL if not.
 */
struct btrfs_delayed_ref_head *
btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
{
        struct btrfs_delayed_ref_root *delayed_refs;

        delayed_refs = &trans->transaction->delayed_refs;
        return find_ref_head(&delayed_refs->href_root, bytenr, 0);
}

void btrfs_delayed_ref_exit(void)
{
        if (btrfs_delayed_ref_head_cachep)
                kmem_cache_destroy(btrfs_delayed_ref_head_cachep);
        if (btrfs_delayed_tree_ref_cachep)
                kmem_cache_destroy(btrfs_delayed_tree_ref_cachep);
        if (btrfs_delayed_data_ref_cachep)
                kmem_cache_destroy(btrfs_delayed_data_ref_cachep);
        if (btrfs_delayed_extent_op_cachep)
                kmem_cache_destroy(btrfs_delayed_extent_op_cachep);
}

int btrfs_delayed_ref_init(void)
{
        btrfs_delayed_ref_head_cachep = kmem_cache_create(
                                "btrfs_delayed_ref_head",
                                sizeof(struct btrfs_delayed_ref_head), 0,
                                SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_delayed_ref_head_cachep)
                goto fail;

        btrfs_delayed_tree_ref_cachep = kmem_cache_create(
                                "btrfs_delayed_tree_ref",
                                sizeof(struct btrfs_delayed_tree_ref), 0,
                                SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_delayed_tree_ref_cachep)
                goto fail;

        btrfs_delayed_data_ref_cachep = kmem_cache_create(
                                "btrfs_delayed_data_ref",
                                sizeof(struct btrfs_delayed_data_ref), 0,
                                SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_delayed_data_ref_cachep)
                goto fail;

        btrfs_delayed_extent_op_cachep = kmem_cache_create(
                                "btrfs_delayed_extent_op",
                                sizeof(struct btrfs_delayed_extent_op), 0,
                                SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_delayed_extent_op_cachep)
                goto fail;

        return 0;
fail:
        btrfs_delayed_ref_exit();
        return -ENOMEM;
}