bpf: Prevent memory disambiguation attack

[linux/fpc-iii.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"
#include "qgroup.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 *ref1,
                          struct btrfs_delayed_tree_ref *ref2)
{
        if (ref1->node.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 *ref1,
                          struct btrfs_delayed_data_ref *ref2)
{
        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;
}

static int comp_refs(struct btrfs_delayed_ref_node *ref1,
                     struct btrfs_delayed_ref_node *ref2,
                     bool check_seq)
{
        int ret = 0;

        if (ref1->type < ref2->type)
                return -1;
        if (ref1->type > ref2->type)
                return 1;
        if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
            ref1->type == BTRFS_SHARED_BLOCK_REF_KEY)
                ret = comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref1),
                                     btrfs_delayed_node_to_tree_ref(ref2));
        else
                ret = comp_data_refs(btrfs_delayed_node_to_data_ref(ref1),
                                     btrfs_delayed_node_to_data_ref(ref2));
        if (ret)
                return ret;
        if (check_seq) {
                if (ref1->seq < ref2->seq)
                        return -1;
                if (ref1->seq > ref2->seq)
                        return 1;
        }
        return 0;
}

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

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

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

static struct btrfs_delayed_ref_node* tree_insert(struct rb_root *root,
                struct btrfs_delayed_ref_node *ins)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *node = &ins->ref_node;
        struct rb_node *parent_node = NULL;
        struct btrfs_delayed_ref_node *entry;

        while (*p) {
                int comp;

                parent_node = *p;
                entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
                                 ref_node);
                comp = comp_refs(ins, entry, true);
                if (comp < 0)
                        p = &(*p)->rb_left;
                else if (comp > 0)
                        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->bytenr)
                        n = n->rb_left;
                else if (bytenr > entry->bytenr)
                        n = n->rb_right;
                else
                        return entry;
        }
        if (entry && return_bigger) {
                if (bytenr > entry->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;

        refcount_inc(&head->refs);
        spin_unlock(&delayed_refs->lock);

        mutex_lock(&head->mutex);
        spin_lock(&delayed_refs->lock);
        if (RB_EMPTY_NODE(&head->href_node)) {
                mutex_unlock(&head->mutex);
                btrfs_put_delayed_ref_head(head);
                return -EAGAIN;
        }
        btrfs_put_delayed_ref_head(head);
        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)
{
        assert_spin_locked(&head->lock);
        rb_erase(&ref->ref_node, &head->ref_tree);
        RB_CLEAR_NODE(&ref->ref_node);
        if (!list_empty(&ref->add_list))
                list_del(&ref->add_list);
        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 bool 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 btrfs_delayed_ref_node *next;
        struct rb_node *node = rb_next(&ref->ref_node);
        bool done = false;

        while (!done && node) {
                int mod;

                next = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
                node = rb_next(node);
                if (seq && next->seq >= seq)
                        break;
                if (comp_refs(ref, next, false))
                        break;

                if (ref->action == next->action) {
                        mod = next->ref_mod;
                } else {
                        if (ref->ref_mod < next->ref_mod) {
                                swap(ref, next);
                                done = true;
                        }
                        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 = true;
                } else {
                        /*
                         * 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 btrfs_delayed_ref_node *ref;
        struct rb_node *node;
        u64 seq = 0;

        assert_spin_locked(&head->lock);

        if (RB_EMPTY_ROOT(&head->ref_tree))
                return;

        /* We don't have too many refs to merge for data. */
        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);

again:
        for (node = rb_first(&head->ref_tree); node; node = rb_next(node)) {
                ref = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
                if (seq && ref->seq >= seq)
                        continue;
                if (merge_ref(trans, delayed_refs, head, ref, seq))
                        goto again;
        }
}

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) {
                        btrfs_debug(fs_info,
                                "holding back delayed_ref %#x.%x, lowest is %#x.%x (%p)",
                                (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->bytenr +
                head->num_bytes;
        return head;
}

/*
 * Helper to insert the ref_node to the tail or merge with tail.
 *
 * Return 0 for insert.
 * Return >0 for merge.
 */
static int insert_delayed_ref(struct btrfs_trans_handle *trans,
                              struct btrfs_delayed_ref_root *root,
                              struct btrfs_delayed_ref_head *href,
                              struct btrfs_delayed_ref_node *ref)
{
        struct btrfs_delayed_ref_node *exist;
        int mod;
        int ret = 0;

        spin_lock(&href->lock);
        exist = tree_insert(&href->ref_tree, ref);
        if (!exist)
                goto inserted;

        /* Now we are sure we can merge */
        ret = 1;
        if (exist->action == ref->action) {
                mod = ref->ref_mod;
        } else {
                /* Need to change action */
                if (exist->ref_mod < ref->ref_mod) {
                        exist->action = ref->action;
                        mod = -exist->ref_mod;
                        exist->ref_mod = ref->ref_mod;
                        if (ref->action == BTRFS_ADD_DELAYED_REF)
                                list_add_tail(&exist->add_list,
                                              &href->ref_add_list);
                        else if (ref->action == BTRFS_DROP_DELAYED_REF) {
                                ASSERT(!list_empty(&exist->add_list));
                                list_del(&exist->add_list);
                        } else {
                                ASSERT(0);
                        }
                } else
                        mod = -ref->ref_mod;
        }
        exist->ref_mod += mod;

        /* remove existing tail if its ref_mod is zero */
        if (exist->ref_mod == 0)
                drop_delayed_ref(trans, root, href, exist);
        spin_unlock(&href->lock);
        return ret;
inserted:
        if (ref->action == BTRFS_ADD_DELAYED_REF)
                list_add_tail(&ref->add_list, &href->ref_add_list);
        atomic_inc(&root->num_entries);
        trans->delayed_ref_updates++;
        spin_unlock(&href->lock);
        return ret;
}

/*
 * 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_root *delayed_refs,
                         struct btrfs_delayed_ref_head *existing,
                         struct btrfs_delayed_ref_head *update,
                         int *old_ref_mod_ret)
{
        int old_ref_mod;

        BUG_ON(existing->is_data != update->is_data);

        spin_lock(&existing->lock);
        if (update->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->must_insert_reserved = update->must_insert_reserved;

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

        }

        if (update->extent_op) {
                if (!existing->extent_op) {
                        existing->extent_op = update->extent_op;
                } else {
                        if (update->extent_op->update_key) {
                                memcpy(&existing->extent_op->key,
                                       &update->extent_op->key,
                                       sizeof(update->extent_op->key));
                                existing->extent_op->update_key = true;
                        }
                        if (update->extent_op->update_flags) {
                                existing->extent_op->flags_to_set |=
                                        update->extent_op->flags_to_set;
                                existing->extent_op->update_flags = true;
                        }
                        btrfs_free_delayed_extent_op(update->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.
         */
        old_ref_mod = existing->total_ref_mod;
        if (old_ref_mod_ret)
                *old_ref_mod_ret = old_ref_mod;
        existing->ref_mod += update->ref_mod;
        existing->total_ref_mod += update->ref_mod;

        /*
         * If we are going to from a positive ref mod to a negative or vice
         * versa we need to make sure to adjust pending_csums accordingly.
         */
        if (existing->is_data) {
                if (existing->total_ref_mod >= 0 && old_ref_mod < 0)
                        delayed_refs->pending_csums -= existing->num_bytes;
                if (existing->total_ref_mod < 0 && old_ref_mod >= 0)
                        delayed_refs->pending_csums += existing->num_bytes;
        }
        spin_unlock(&existing->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_head *head_ref,
                     struct btrfs_qgroup_extent_record *qrecord,
                     u64 bytenr, u64 num_bytes, u64 ref_root, u64 reserved,
                     int action, int is_data, int is_system,
                     int *qrecord_inserted_ret,
                     int *old_ref_mod, int *new_ref_mod)

{
        struct btrfs_delayed_ref_head *existing;
        struct btrfs_delayed_ref_root *delayed_refs;
        int count_mod = 1;
        int must_insert_reserved = 0;
        int qrecord_inserted = 0;

        /* If reserved is provided, it must be a data extent. */
        BUG_ON(!is_data && reserved);

        /*
         * 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;

        refcount_set(&head_ref->refs, 1);
        head_ref->bytenr = bytenr;
        head_ref->num_bytes = num_bytes;
        head_ref->ref_mod = count_mod;
        head_ref->must_insert_reserved = must_insert_reserved;
        head_ref->is_data = is_data;
        head_ref->is_system = is_system;
        head_ref->ref_tree = RB_ROOT;
        INIT_LIST_HEAD(&head_ref->ref_add_list);
        RB_CLEAR_NODE(&head_ref->href_node);
        head_ref->processing = 0;
        head_ref->total_ref_mod = count_mod;
        head_ref->qgroup_reserved = 0;
        head_ref->qgroup_ref_root = 0;
        spin_lock_init(&head_ref->lock);
        mutex_init(&head_ref->mutex);

        /* Record qgroup extent info if provided */
        if (qrecord) {
                if (ref_root && reserved) {
                        head_ref->qgroup_ref_root = ref_root;
                        head_ref->qgroup_reserved = reserved;
                }

                qrecord->bytenr = bytenr;
                qrecord->num_bytes = num_bytes;
                qrecord->old_roots = NULL;

                if(btrfs_qgroup_trace_extent_nolock(fs_info,
                                        delayed_refs, qrecord))
                        kfree(qrecord);
                else
                        qrecord_inserted = 1;
        }

        trace_add_delayed_ref_head(fs_info, head_ref, action);

        existing = htree_insert(&delayed_refs->href_root,
                                &head_ref->href_node);
        if (existing) {
                WARN_ON(ref_root && reserved && existing->qgroup_ref_root
                        && existing->qgroup_reserved);
                update_existing_head_ref(delayed_refs, existing, head_ref,
                                         old_ref_mod);
                /*
                 * 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 {
                if (old_ref_mod)
                        *old_ref_mod = 0;
                if (is_data && count_mod < 0)
                        delayed_refs->pending_csums += num_bytes;
                delayed_refs->num_heads++;
                delayed_refs->num_heads_ready++;
                atomic_inc(&delayed_refs->num_entries);
                trans->delayed_ref_updates++;
        }
        if (qrecord_inserted_ret)
                *qrecord_inserted_ret = qrecord_inserted;
        if (new_ref_mod)
                *new_ref_mod = head_ref->total_ref_mod;
        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)
{
        struct btrfs_delayed_tree_ref *full_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        u64 seq = 0;
        int ret;

        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 */
        refcount_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->seq = seq;
        RB_CLEAR_NODE(&ref->ref_node);
        INIT_LIST_HEAD(&ref->add_list);

        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(fs_info, ref, full_ref, action);

        ret = insert_delayed_ref(trans, delayed_refs, head_ref, ref);

        /*
         * XXX: memory should be freed at the same level allocated.
         * But bad practice is anywhere... Follow it now. Need cleanup.
         */
        if (ret > 0)
                kmem_cache_free(btrfs_delayed_tree_ref_cachep, full_ref);
}

/*
 * 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)
{
        struct btrfs_delayed_data_ref *full_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        u64 seq = 0;
        int ret;

        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 */
        refcount_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->seq = seq;
        RB_CLEAR_NODE(&ref->ref_node);
        INIT_LIST_HEAD(&ref->add_list);

        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(fs_info, ref, full_ref, action);

        ret = insert_delayed_ref(trans, delayed_refs, head_ref, ref);
        if (ret > 0)
                kmem_cache_free(btrfs_delayed_data_ref_cachep, full_ref);
}

/*
 * 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 *old_ref_mod, int *new_ref_mod)
{
        struct btrfs_delayed_tree_ref *ref;
        struct btrfs_delayed_ref_head *head_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_qgroup_extent_record *record = NULL;
        int qrecord_inserted;
        int is_system = (ref_root == BTRFS_CHUNK_TREE_OBJECTID);

        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)
                goto free_ref;

        if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
            is_fstree(ref_root)) {
                record = kmalloc(sizeof(*record), GFP_NOFS);
                if (!record)
                        goto free_head_ref;
        }

        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, record,
                                        bytenr, num_bytes, 0, 0, action, 0,
                                        is_system, &qrecord_inserted,
                                        old_ref_mod, new_ref_mod);

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

        if (qrecord_inserted)
                btrfs_qgroup_trace_extent_post(fs_info, record);

        return 0;

free_head_ref:
        kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
free_ref:
        kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);

        return -ENOMEM;
}

/*
 * 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, u64 reserved, int action,
                               int *old_ref_mod, int *new_ref_mod)
{
        struct btrfs_delayed_data_ref *ref;
        struct btrfs_delayed_ref_head *head_ref;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct btrfs_qgroup_extent_record *record = NULL;
        int qrecord_inserted;

        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;
        }

        if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
            is_fstree(ref_root)) {
                record = kmalloc(sizeof(*record), GFP_NOFS);
                if (!record) {
                        kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
                        kmem_cache_free(btrfs_delayed_ref_head_cachep,
                                        head_ref);
                        return -ENOMEM;
                }
        }

        head_ref->extent_op = NULL;

        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, record,
                                        bytenr, num_bytes, ref_root, reserved,
                                        action, 1, 0, &qrecord_inserted,
                                        old_ref_mod, new_ref_mod);

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

        if (qrecord_inserted)
                return btrfs_qgroup_trace_extent_post(fs_info, record);
        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);

        /*
         * extent_ops just modify the flags of an extent and they don't result
         * in ref count changes, hence it's safe to pass false/0 for is_system
         * argument
         */
        add_delayed_ref_head(fs_info, trans, head_ref, NULL, bytenr,
                             num_bytes, 0, 0, BTRFS_UPDATE_DELAYED_HEAD,
                             extent_op->is_data, 0, NULL, NULL, NULL);

        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_delayed_ref_root *delayed_refs, u64 bytenr)
{
        return find_ref_head(&delayed_refs->href_root, bytenr, 0);
}

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

int __init 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_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_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_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_MEM_SPREAD, NULL);
        if (!btrfs_delayed_extent_op_cachep)
                goto fail;

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