Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1160 insertions, 0 deletions

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
new file mode 100644
index 0000000000..9fe4ccca50
--- /dev/null
+++ b/fs/btrfs/delayed-ref.c
@@ -0,0 +1,1160 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2009 Oracle.  All rights reserved.
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include "messages.h"
+#include "ctree.h"
+#include "delayed-ref.h"
+#include "transaction.h"
+#include "qgroup.h"
+#include "space-info.h"
+#include "tree-mod-log.h"
+#include "fs.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.
+ */
+
+bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
+	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
+	bool ret = false;
+	u64 reserved;
+
+	spin_lock(&global_rsv->lock);
+	reserved = global_rsv->reserved;
+	spin_unlock(&global_rsv->lock);
+
+	/*
+	 * Since the global reserve is just kind of magic we don't really want
+	 * to rely on it to save our bacon, so if our size is more than the
+	 * delayed_refs_rsv and the global rsv then it's time to think about
+	 * bailing.
+	 */
+	spin_lock(&delayed_refs_rsv->lock);
+	reserved += delayed_refs_rsv->reserved;
+	if (delayed_refs_rsv->size >= reserved)
+		ret = true;
+	spin_unlock(&delayed_refs_rsv->lock);
+	return ret;
+}
+
+/*
+ * Release a ref head's reservation.
+ *
+ * @fs_info:  the filesystem
+ * @nr:       number of items to drop
+ *
+ * Drops the delayed ref head's count from the delayed refs rsv and free any
+ * excess reservation we had.
+ */
+void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr)
+{
+	struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
+	const u64 num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, nr);
+	u64 released = 0;
+
+	released = btrfs_block_rsv_release(fs_info, block_rsv, num_bytes, NULL);
+	if (released)
+		trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
+					      0, released, 0);
+}
+
+/*
+ * Adjust the size of the delayed refs rsv.
+ *
+ * This is to be called anytime we may have adjusted trans->delayed_ref_updates,
+ * it'll calculate the additional size and add it to the delayed_refs_rsv.
+ */
+void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
+	u64 num_bytes;
+
+	if (!trans->delayed_ref_updates)
+		return;
+
+	num_bytes = btrfs_calc_delayed_ref_bytes(fs_info,
+						 trans->delayed_ref_updates);
+
+	spin_lock(&delayed_rsv->lock);
+	delayed_rsv->size += num_bytes;
+	delayed_rsv->full = false;
+	spin_unlock(&delayed_rsv->lock);
+	trans->delayed_ref_updates = 0;
+}
+
+/*
+ * Transfer bytes to our delayed refs rsv.
+ *
+ * @fs_info:   the filesystem
+ * @num_bytes: number of bytes to transfer
+ *
+ * This transfers up to the num_bytes amount, previously reserved, to the
+ * delayed_refs_rsv.  Any extra bytes are returned to the space info.
+ */
+void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
+				       u64 num_bytes)
+{
+	struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
+	u64 to_free = 0;
+
+	spin_lock(&delayed_refs_rsv->lock);
+	if (delayed_refs_rsv->size > delayed_refs_rsv->reserved) {
+		u64 delta = delayed_refs_rsv->size -
+			delayed_refs_rsv->reserved;
+		if (num_bytes > delta) {
+			to_free = num_bytes - delta;
+			num_bytes = delta;
+		}
+	} else {
+		to_free = num_bytes;
+		num_bytes = 0;
+	}
+
+	if (num_bytes)
+		delayed_refs_rsv->reserved += num_bytes;
+	if (delayed_refs_rsv->reserved >= delayed_refs_rsv->size)
+		delayed_refs_rsv->full = true;
+	spin_unlock(&delayed_refs_rsv->lock);
+
+	if (num_bytes)
+		trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
+					      0, num_bytes, 1);
+	if (to_free)
+		btrfs_space_info_free_bytes_may_use(fs_info,
+				delayed_refs_rsv->space_info, to_free);
+}
+
+/*
+ * Refill based on our delayed refs usage.
+ *
+ * @fs_info: the filesystem
+ * @flush:   control how we can flush for this reservation.
+ *
+ * This will refill the delayed block_rsv up to 1 items size worth of space and
+ * will return -ENOSPC if we can't make the reservation.
+ */
+int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
+				  enum btrfs_reserve_flush_enum flush)
+{
+	struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
+	u64 limit = btrfs_calc_delayed_ref_bytes(fs_info, 1);
+	u64 num_bytes = 0;
+	u64 refilled_bytes;
+	u64 to_free;
+	int ret = -ENOSPC;
+
+	spin_lock(&block_rsv->lock);
+	if (block_rsv->reserved < block_rsv->size) {
+		num_bytes = block_rsv->size - block_rsv->reserved;
+		num_bytes = min(num_bytes, limit);
+	}
+	spin_unlock(&block_rsv->lock);
+
+	if (!num_bytes)
+		return 0;
+
+	ret = btrfs_reserve_metadata_bytes(fs_info, block_rsv, num_bytes, flush);
+	if (ret)
+		return ret;
+
+	/*
+	 * We may have raced with someone else, so check again if we the block
+	 * reserve is still not full and release any excess space.
+	 */
+	spin_lock(&block_rsv->lock);
+	if (block_rsv->reserved < block_rsv->size) {
+		u64 needed = block_rsv->size - block_rsv->reserved;
+
+		if (num_bytes >= needed) {
+			block_rsv->reserved += needed;
+			block_rsv->full = true;
+			to_free = num_bytes - needed;
+			refilled_bytes = needed;
+		} else {
+			block_rsv->reserved += num_bytes;
+			to_free = 0;
+			refilled_bytes = num_bytes;
+		}
+	} else {
+		to_free = num_bytes;
+		refilled_bytes = 0;
+	}
+	spin_unlock(&block_rsv->lock);
+
+	if (to_free > 0)
+		btrfs_space_info_free_bytes_may_use(fs_info, block_rsv->space_info,
+						    to_free);
+
+	if (refilled_bytes > 0)
+		trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv", 0,
+					      refilled_bytes, 1);
+	return 0;
+}
+
+/*
+ * 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_cached *root,
+						   struct rb_node *node)
+{
+	struct rb_node **p = &root->rb_root.rb_node;
+	struct rb_node *parent_node = NULL;
+	struct btrfs_delayed_ref_head *entry;
+	struct btrfs_delayed_ref_head *ins;
+	u64 bytenr;
+	bool leftmost = true;
+
+	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;
+			leftmost = false;
+		} else {
+			return entry;
+		}
+	}
+
+	rb_link_node(node, parent_node, p);
+	rb_insert_color_cached(node, root, leftmost);
+	return NULL;
+}
+
+static struct btrfs_delayed_ref_node* tree_insert(struct rb_root_cached *root,
+		struct btrfs_delayed_ref_node *ins)
+{
+	struct rb_node **p = &root->rb_root.rb_node;
+	struct rb_node *node = &ins->ref_node;
+	struct rb_node *parent_node = NULL;
+	struct btrfs_delayed_ref_node *entry;
+	bool leftmost = true;
+
+	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;
+			leftmost = false;
+		} else {
+			return entry;
+		}
+	}
+
+	rb_link_node(node, parent_node, p);
+	rb_insert_color_cached(node, root, leftmost);
+	return NULL;
+}
+
+static struct btrfs_delayed_ref_head *find_first_ref_head(
+		struct btrfs_delayed_ref_root *dr)
+{
+	struct rb_node *n;
+	struct btrfs_delayed_ref_head *entry;
+
+	n = rb_first_cached(&dr->href_root);
+	if (!n)
+		return NULL;
+
+	entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);
+
+	return entry;
+}
+
+/*
+ * Find a 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 btrfs_delayed_ref_root *dr, u64 bytenr,
+		bool return_bigger)
+{
+	struct rb_root *root = &dr->href_root.rb_root;
+	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)
+				return NULL;
+			entry = rb_entry(n, struct btrfs_delayed_ref_head,
+					 href_node);
+		}
+		return entry;
+	}
+	return NULL;
+}
+
+int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
+			   struct btrfs_delayed_ref_head *head)
+{
+	lockdep_assert_held(&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_delayed_ref_root *delayed_refs,
+				    struct btrfs_delayed_ref_head *head,
+				    struct btrfs_delayed_ref_node *ref)
+{
+	lockdep_assert_held(&head->lock);
+	rb_erase_cached(&ref->ref_node, &head->ref_tree);
+	RB_CLEAR_NODE(&ref->ref_node);
+	if (!list_empty(&ref->add_list))
+		list_del(&ref->add_list);
+	btrfs_put_delayed_ref(ref);
+	atomic_dec(&delayed_refs->num_entries);
+}
+
+static bool merge_ref(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(delayed_refs, head, next);
+		ref->ref_mod += mod;
+		if (ref->ref_mod == 0) {
+			drop_delayed_ref(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_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;
+
+	lockdep_assert_held(&head->lock);
+
+	if (RB_EMPTY_ROOT(&head->ref_tree.rb_root))
+		return;
+
+	/* We don't have too many refs to merge for data. */
+	if (head->is_data)
+		return;
+
+	seq = btrfs_tree_mod_log_lowest_seq(fs_info);
+again:
+	for (node = rb_first_cached(&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(delayed_refs, head, ref, seq))
+			goto again;
+	}
+}
+
+int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq)
+{
+	int ret = 0;
+	u64 min_seq = btrfs_tree_mod_log_lowest_seq(fs_info);
+
+	if (min_seq != 0 && seq >= min_seq) {
+		btrfs_debug(fs_info,
+			    "holding back delayed_ref %llu, lowest is %llu",
+			    seq, min_seq);
+		ret = 1;
+	}
+
+	return ret;
+}
+
+struct btrfs_delayed_ref_head *btrfs_select_ref_head(
+		struct btrfs_delayed_ref_root *delayed_refs)
+{
+	struct btrfs_delayed_ref_head *head;
+
+	lockdep_assert_held(&delayed_refs->lock);
+again:
+	head = find_ref_head(delayed_refs, delayed_refs->run_delayed_start,
+			     true);
+	if (!head && delayed_refs->run_delayed_start != 0) {
+		delayed_refs->run_delayed_start = 0;
+		head = find_first_ref_head(delayed_refs);
+	}
+	if (!head)
+		return NULL;
+
+	while (head->processing) {
+		struct rb_node *node;
+
+		node = rb_next(&head->href_node);
+		if (!node) {
+			if (delayed_refs->run_delayed_start == 0)
+				return NULL;
+			delayed_refs->run_delayed_start = 0;
+			goto again;
+		}
+		head = rb_entry(node, struct btrfs_delayed_ref_head,
+				href_node);
+	}
+
+	head->processing = true;
+	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;
+}
+
+void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
+			   struct btrfs_delayed_ref_head *head)
+{
+	lockdep_assert_held(&delayed_refs->lock);
+	lockdep_assert_held(&head->lock);
+
+	rb_erase_cached(&head->href_node, &delayed_refs->href_root);
+	RB_CLEAR_NODE(&head->href_node);
+	atomic_dec(&delayed_refs->num_entries);
+	delayed_refs->num_heads--;
+	if (!head->processing)
+		delayed_refs->num_heads_ready--;
+}
+
+/*
+ * Helper to insert the ref_node to the tail or merge with tail.
+ *
+ * Return false if the ref was inserted.
+ * Return true if the ref was merged into an existing one (and therefore can be
+ * freed by the caller).
+ */
+static bool insert_delayed_ref(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;
+
+	spin_lock(&href->lock);
+	exist = tree_insert(&href->ref_tree, ref);
+	if (!exist) {
+		if (ref->action == BTRFS_ADD_DELAYED_REF)
+			list_add_tail(&ref->add_list, &href->ref_add_list);
+		atomic_inc(&root->num_entries);
+		spin_unlock(&href->lock);
+		return false;
+	}
+
+	/* Now we are sure we can merge */
+	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(root, href, exist);
+	spin_unlock(&href->lock);
+	return true;
+}
+
+/*
+ * 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_trans_handle *trans,
+			 struct btrfs_delayed_ref_head *existing,
+			 struct btrfs_delayed_ref_head *update)
+{
+	struct btrfs_delayed_ref_root *delayed_refs =
+		&trans->transaction->delayed_refs;
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	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;
+	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) {
+		u64 csum_leaves =
+			btrfs_csum_bytes_to_leaves(fs_info,
+						   existing->num_bytes);
+
+		if (existing->total_ref_mod >= 0 && old_ref_mod < 0) {
+			delayed_refs->pending_csums -= existing->num_bytes;
+			btrfs_delayed_refs_rsv_release(fs_info, csum_leaves);
+		}
+		if (existing->total_ref_mod < 0 && old_ref_mod >= 0) {
+			delayed_refs->pending_csums += existing->num_bytes;
+			trans->delayed_ref_updates += csum_leaves;
+		}
+	}
+
+	spin_unlock(&existing->lock);
+}
+
+static void init_delayed_ref_head(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, bool is_data,
+				  bool is_system)
+{
+	int count_mod = 1;
+	bool must_insert_reserved = false;
+
+	/* If reserved is provided, it must be a data extent. */
+	BUG_ON(!is_data && reserved);
+
+	switch (action) {
+	case BTRFS_UPDATE_DELAYED_HEAD:
+		count_mod = 0;
+		break;
+	case BTRFS_DROP_DELAYED_REF:
+		/*
+		 * The head node stores the sum of all the mods, so dropping a ref
+		 * should drop the sum in the head node by one.
+		 */
+		count_mod = -1;
+		break;
+	case BTRFS_ADD_DELAYED_EXTENT:
+		/*
+		 * 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.
+		 */
+		must_insert_reserved = true;
+		break;
+	}
+
+	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_CACHED;
+	INIT_LIST_HEAD(&head_ref->ref_add_list);
+	RB_CLEAR_NODE(&head_ref->href_node);
+	head_ref->processing = false;
+	head_ref->total_ref_mod = count_mod;
+	spin_lock_init(&head_ref->lock);
+	mutex_init(&head_ref->mutex);
+
+	if (qrecord) {
+		if (ref_root && reserved) {
+			qrecord->data_rsv = reserved;
+			qrecord->data_rsv_refroot = ref_root;
+		}
+		qrecord->bytenr = bytenr;
+		qrecord->num_bytes = num_bytes;
+		qrecord->old_roots = NULL;
+	}
+}
+
+/*
+ * 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_trans_handle *trans,
+		     struct btrfs_delayed_ref_head *head_ref,
+		     struct btrfs_qgroup_extent_record *qrecord,
+		     int action, bool *qrecord_inserted_ret)
+{
+	struct btrfs_delayed_ref_head *existing;
+	struct btrfs_delayed_ref_root *delayed_refs;
+	bool qrecord_inserted = false;
+
+	delayed_refs = &trans->transaction->delayed_refs;
+
+	/* Record qgroup extent info if provided */
+	if (qrecord) {
+		if (btrfs_qgroup_trace_extent_nolock(trans->fs_info,
+					delayed_refs, qrecord))
+			kfree(qrecord);
+		else
+			qrecord_inserted = true;
+	}
+
+	trace_add_delayed_ref_head(trans->fs_info, head_ref, action);
+
+	existing = htree_insert(&delayed_refs->href_root,
+				&head_ref->href_node);
+	if (existing) {
+		update_existing_head_ref(trans, existing, head_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 {
+		if (head_ref->is_data && head_ref->ref_mod < 0) {
+			delayed_refs->pending_csums += head_ref->num_bytes;
+			trans->delayed_ref_updates +=
+				btrfs_csum_bytes_to_leaves(trans->fs_info,
+							   head_ref->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;
+
+	return head_ref;
+}
+
+/*
+ * init_delayed_ref_common - Initialize the structure which represents a
+ *			     modification to a an extent.
+ *
+ * @fs_info:    Internal to the mounted filesystem mount structure.
+ *
+ * @ref:	The structure which is going to be initialized.
+ *
+ * @bytenr:	The logical address of the extent for which a modification is
+ *		going to be recorded.
+ *
+ * @num_bytes:  Size of the extent whose modification is being recorded.
+ *
+ * @ref_root:	The id of the root where this modification has originated, this
+ *		can be either one of the well-known metadata trees or the
+ *		subvolume id which references this extent.
+ *
+ * @action:	Can be one of BTRFS_ADD_DELAYED_REF/BTRFS_DROP_DELAYED_REF or
+ *		BTRFS_ADD_DELAYED_EXTENT
+ *
+ * @ref_type:	Holds the type of the extent which is being recorded, can be
+ *		one of BTRFS_SHARED_BLOCK_REF_KEY/BTRFS_TREE_BLOCK_REF_KEY
+ *		when recording a metadata extent or BTRFS_SHARED_DATA_REF_KEY/
+ *		BTRFS_EXTENT_DATA_REF_KEY when recording data extent
+ */
+static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
+				    struct btrfs_delayed_ref_node *ref,
+				    u64 bytenr, u64 num_bytes, u64 ref_root,
+				    int action, u8 ref_type)
+{
+	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);
+
+	refcount_set(&ref->refs, 1);
+	ref->bytenr = bytenr;
+	ref->num_bytes = num_bytes;
+	ref->ref_mod = 1;
+	ref->action = action;
+	ref->seq = seq;
+	ref->type = ref_type;
+	RB_CLEAR_NODE(&ref->ref_node);
+	INIT_LIST_HEAD(&ref->add_list);
+}
+
+/*
+ * 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_trans_handle *trans,
+			       struct btrfs_ref *generic_ref,
+			       struct btrfs_delayed_extent_op *extent_op)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	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;
+	bool qrecord_inserted;
+	bool is_system;
+	bool merged;
+	int action = generic_ref->action;
+	int level = generic_ref->tree_ref.level;
+	u64 bytenr = generic_ref->bytenr;
+	u64 num_bytes = generic_ref->len;
+	u64 parent = generic_ref->parent;
+	u8 ref_type;
+
+	is_system = (generic_ref->tree_ref.owning_root == BTRFS_CHUNK_TREE_OBJECTID);
+
+	ASSERT(generic_ref->type == BTRFS_REF_METADATA && generic_ref->action);
+	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;
+	}
+
+	if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
+	    !generic_ref->skip_qgroup) {
+		record = kzalloc(sizeof(*record), GFP_NOFS);
+		if (!record) {
+			kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
+			kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
+			return -ENOMEM;
+		}
+	}
+
+	if (parent)
+		ref_type = BTRFS_SHARED_BLOCK_REF_KEY;
+	else
+		ref_type = BTRFS_TREE_BLOCK_REF_KEY;
+
+	init_delayed_ref_common(fs_info, &ref->node, bytenr, num_bytes,
+				generic_ref->tree_ref.owning_root, action,
+				ref_type);
+	ref->root = generic_ref->tree_ref.owning_root;
+	ref->parent = parent;
+	ref->level = level;
+
+	init_delayed_ref_head(head_ref, record, bytenr, num_bytes,
+			      generic_ref->tree_ref.owning_root, 0, action,
+			      false, is_system);
+	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(trans, head_ref, record,
+					action, &qrecord_inserted);
+
+	merged = insert_delayed_ref(delayed_refs, head_ref, &ref->node);
+	spin_unlock(&delayed_refs->lock);
+
+	/*
+	 * Need to update the delayed_refs_rsv with any changes we may have
+	 * made.
+	 */
+	btrfs_update_delayed_refs_rsv(trans);
+
+	trace_add_delayed_tree_ref(fs_info, &ref->node, ref,
+				   action == BTRFS_ADD_DELAYED_EXTENT ?
+				   BTRFS_ADD_DELAYED_REF : action);
+	if (merged)
+		kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
+
+	if (qrecord_inserted)
+		btrfs_qgroup_trace_extent_post(trans, record);
+
+	return 0;
+}
+
+/*
+ * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
+ */
+int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
+			       struct btrfs_ref *generic_ref,
+			       u64 reserved)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	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;
+	bool qrecord_inserted;
+	int action = generic_ref->action;
+	bool merged;
+	u64 bytenr = generic_ref->bytenr;
+	u64 num_bytes = generic_ref->len;
+	u64 parent = generic_ref->parent;
+	u64 ref_root = generic_ref->data_ref.owning_root;
+	u64 owner = generic_ref->data_ref.ino;
+	u64 offset = generic_ref->data_ref.offset;
+	u8 ref_type;
+
+	ASSERT(generic_ref->type == BTRFS_REF_DATA && action);
+	ref = kmem_cache_alloc(btrfs_delayed_data_ref_cachep, GFP_NOFS);
+	if (!ref)
+		return -ENOMEM;
+
+	if (parent)
+	        ref_type = BTRFS_SHARED_DATA_REF_KEY;
+	else
+	        ref_type = BTRFS_EXTENT_DATA_REF_KEY;
+	init_delayed_ref_common(fs_info, &ref->node, bytenr, num_bytes,
+				ref_root, action, ref_type);
+	ref->root = ref_root;
+	ref->parent = parent;
+	ref->objectid = owner;
+	ref->offset = offset;
+
+
+	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) &&
+	    !generic_ref->skip_qgroup) {
+		record = kzalloc(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;
+		}
+	}
+
+	init_delayed_ref_head(head_ref, record, bytenr, num_bytes, ref_root,
+			      reserved, action, true, false);
+	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(trans, head_ref, record,
+					action, &qrecord_inserted);
+
+	merged = insert_delayed_ref(delayed_refs, head_ref, &ref->node);
+	spin_unlock(&delayed_refs->lock);
+
+	/*
+	 * Need to update the delayed_refs_rsv with any changes we may have
+	 * made.
+	 */
+	btrfs_update_delayed_refs_rsv(trans);
+
+	trace_add_delayed_data_ref(trans->fs_info, &ref->node, ref,
+				   action == BTRFS_ADD_DELAYED_EXTENT ?
+				   BTRFS_ADD_DELAYED_REF : action);
+	if (merged)
+		kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
+
+
+	if (qrecord_inserted)
+		return btrfs_qgroup_trace_extent_post(trans, record);
+	return 0;
+}
+
+int btrfs_add_delayed_extent_op(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;
+
+	init_delayed_ref_head(head_ref, NULL, bytenr, num_bytes, 0, 0,
+			      BTRFS_UPDATE_DELAYED_HEAD, false, false);
+	head_ref->extent_op = extent_op;
+
+	delayed_refs = &trans->transaction->delayed_refs;
+	spin_lock(&delayed_refs->lock);
+
+	add_delayed_ref_head(trans, head_ref, NULL, BTRFS_UPDATE_DELAYED_HEAD,
+			     NULL);
+
+	spin_unlock(&delayed_refs->lock);
+
+	/*
+	 * Need to update the delayed_refs_rsv with any changes we may have
+	 * made.
+	 */
+	btrfs_update_delayed_refs_rsv(trans);
+	return 0;
+}
+
+/*
+ * This does a simple search for the head node for a given extent.  Returns the
+ * head node if found, or NULL if not.
+ */
+struct btrfs_delayed_ref_head *
+btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs, u64 bytenr)
+{
+	lockdep_assert_held(&delayed_refs->lock);
+
+	return find_ref_head(delayed_refs, bytenr, false);
+}
+
+void __cold 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;
+}