init android origin source code

1 files changed, 759 insertions, 0 deletions

diff --git a/ANDROID_3.4.5/fs/btrfs/delayed-ref.c b/ANDROID_3.4.5/fs/btrfs/delayed-ref.c
new file mode 100644
index 00000000..69f22e3a
--- /dev/null
+++ b/ANDROID_3.4.5/fs/btrfs/delayed-ref.c
@@ -0,0 +1,759 @@
+/*
+ * 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"
+
+/*
+ * 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)
+{
+	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 *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)
+{
+	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;
+	/* merging of sequenced refs is not allowed */
+	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));
+	} 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);
+		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;
+}
+
+/*
+ * 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_node *find_ref_head(struct rb_root *root,
+				  u64 bytenr,
+				  struct btrfs_delayed_ref_node **last,
+				  int return_bigger)
+{
+	struct rb_node *n;
+	struct btrfs_delayed_ref_node *entry;
+	int cmp = 0;
+
+again:
+	n = root->rb_node;
+	entry = NULL;
+	while (n) {
+		entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
+		WARN_ON(!entry->in_tree);
+		if (last)
+			*last = entry;
+
+		if (bytenr < entry->bytenr)
+			cmp = -1;
+		else if (bytenr > entry->bytenr)
+			cmp = 1;
+		else if (!btrfs_delayed_ref_is_head(entry))
+			cmp = 1;
+		else
+			cmp = 0;
+
+		if (cmp < 0)
+			n = n->rb_left;
+		else if (cmp > 0)
+			n = n->rb_right;
+		else
+			return entry;
+	}
+	if (entry && return_bigger) {
+		if (cmp > 0) {
+			n = rb_next(&entry->rb_node);
+			if (!n)
+				n = rb_first(root);
+			entry = rb_entry(n, struct btrfs_delayed_ref_node,
+					 rb_node);
+			bytenr = entry->bytenr;
+			return_bigger = 0;
+			goto again;
+		}
+		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;
+}
+
+int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
+			    u64 seq)
+{
+	struct seq_list *elem;
+
+	assert_spin_locked(&delayed_refs->lock);
+	if (list_empty(&delayed_refs->seq_head))
+		return 0;
+
+	elem = list_first_entry(&delayed_refs->seq_head, struct seq_list, list);
+	if (seq >= elem->seq) {
+		pr_debug("holding back delayed_ref %llu, lowest is %llu (%p)\n",
+			 seq, elem->seq, delayed_refs);
+		return 1;
+	}
+	return 0;
+}
+
+int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
+			   struct list_head *cluster, u64 start)
+{
+	int count = 0;
+	struct btrfs_delayed_ref_root *delayed_refs;
+	struct rb_node *node;
+	struct btrfs_delayed_ref_node *ref;
+	struct btrfs_delayed_ref_head *head;
+
+	delayed_refs = &trans->transaction->delayed_refs;
+	if (start == 0) {
+		node = rb_first(&delayed_refs->root);
+	} else {
+		ref = NULL;
+		find_ref_head(&delayed_refs->root, start + 1, &ref, 1);
+		if (ref) {
+			node = &ref->rb_node;
+		} else
+			node = rb_first(&delayed_refs->root);
+	}
+again:
+	while (node && count < 32) {
+		ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
+		if (btrfs_delayed_ref_is_head(ref)) {
+			head = btrfs_delayed_node_to_head(ref);
+			if (list_empty(&head->cluster)) {
+				list_add_tail(&head->cluster, cluster);
+				delayed_refs->run_delayed_start =
+					head->node.bytenr;
+				count++;
+
+				WARN_ON(delayed_refs->num_heads_ready == 0);
+				delayed_refs->num_heads_ready--;
+			} else if (count) {
+				/* the goal of the clustering is to find extents
+				 * that are likely to end up in the same extent
+				 * leaf on disk.  So, we don't want them spread
+				 * all over the tree.  Stop now if we've hit
+				 * a head that was already in use
+				 */
+				break;
+			}
+		}
+		node = rb_next(node);
+	}
+	if (count) {
+		return 0;
+	} else if (start) {
+		/*
+		 * we've gone to the end of the rbtree without finding any
+		 * clusters.  start from the beginning and try again
+		 */
+		start = 0;
+		node = rb_first(&delayed_refs->root);
+		goto again;
+	}
+	return 1;
+}
+
+/*
+ * 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_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) {
+			rb_erase(&existing->rb_node,
+				 &delayed_refs->root);
+			existing->in_tree = 0;
+			btrfs_put_delayed_ref(existing);
+			delayed_refs->num_entries--;
+			if (trans->delayed_ref_updates)
+				trans->delayed_ref_updates--;
+		} 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);
+
+	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;
+			}
+			kfree(ref->extent_op);
+		}
+	}
+	/*
+	 * update the reference mod on the head to reflect this new operation
+	 */
+	existing->ref_mod += update->ref_mod;
+}
+
+/*
+ * 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 void 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_node *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;
+
+	INIT_LIST_HEAD(&head_ref->cluster);
+	mutex_init(&head_ref->mutex);
+
+	trace_btrfs_delayed_ref_head(ref, head_ref, action);
+
+	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
+
+	if (existing) {
+		update_existing_head_ref(existing, ref);
+		/*
+		 * we've updated the existing ref, free the newly
+		 * allocated ref
+		 */
+		kfree(head_ref);
+	} else {
+		delayed_refs->num_heads++;
+		delayed_refs->num_heads_ready++;
+		delayed_refs->num_entries++;
+		trans->delayed_ref_updates++;
+	}
+}
+
+/*
+ * 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_node *ref,
+					 u64 bytenr, u64 num_bytes, u64 parent,
+					 u64 ref_root, int level, int action,
+					 int for_cow)
+{
+	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;
+
+	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;
+
+	if (need_ref_seq(for_cow, ref_root))
+		seq = inc_delayed_seq(delayed_refs);
+	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_btrfs_delayed_tree_ref(ref, full_ref, action);
+
+	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
+
+	if (existing) {
+		update_existing_ref(trans, delayed_refs, existing, ref);
+		/*
+		 * we've updated the existing ref, free the newly
+		 * allocated ref
+		 */
+		kfree(full_ref);
+	} else {
+		delayed_refs->num_entries++;
+		trans->delayed_ref_updates++;
+	}
+}
+
+/*
+ * 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_node *ref,
+					 u64 bytenr, u64 num_bytes, u64 parent,
+					 u64 ref_root, u64 owner, u64 offset,
+					 int action, int for_cow)
+{
+	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;
+
+	/* 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;
+
+	if (need_ref_seq(for_cow, ref_root))
+		seq = inc_delayed_seq(delayed_refs);
+	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_btrfs_delayed_data_ref(ref, full_ref, action);
+
+	existing = tree_insert(&delayed_refs->root, &ref->rb_node);
+
+	if (existing) {
+		update_existing_ref(trans, delayed_refs, existing, ref);
+		/*
+		 * we've updated the existing ref, free the newly
+		 * allocated ref
+		 */
+		kfree(full_ref);
+	} else {
+		delayed_refs->num_entries++;
+		trans->delayed_ref_updates++;
+	}
+}
+
+/*
+ * 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 for_cow)
+{
+	struct btrfs_delayed_tree_ref *ref;
+	struct btrfs_delayed_ref_head *head_ref;
+	struct btrfs_delayed_ref_root *delayed_refs;
+
+	BUG_ON(extent_op && extent_op->is_data);
+	ref = kmalloc(sizeof(*ref), GFP_NOFS);
+	if (!ref)
+		return -ENOMEM;
+
+	head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
+	if (!head_ref) {
+		kfree(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
+	 */
+	add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
+				   num_bytes, action, 0);
+
+	add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
+				   num_bytes, parent, ref_root, level, action,
+				   for_cow);
+	if (!need_ref_seq(for_cow, ref_root) &&
+	    waitqueue_active(&delayed_refs->seq_wait))
+		wake_up(&delayed_refs->seq_wait);
+	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 for_cow)
+{
+	struct btrfs_delayed_data_ref *ref;
+	struct btrfs_delayed_ref_head *head_ref;
+	struct btrfs_delayed_ref_root *delayed_refs;
+
+	BUG_ON(extent_op && !extent_op->is_data);
+	ref = kmalloc(sizeof(*ref), GFP_NOFS);
+	if (!ref)
+		return -ENOMEM;
+
+	head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
+	if (!head_ref) {
+		kfree(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
+	 */
+	add_delayed_ref_head(fs_info, trans, &head_ref->node, bytenr,
+				   num_bytes, action, 1);
+
+	add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
+				   num_bytes, parent, ref_root, owner, offset,
+				   action, for_cow);
+	if (!need_ref_seq(for_cow, ref_root) &&
+	    waitqueue_active(&delayed_refs->seq_wait))
+		wake_up(&delayed_refs->seq_wait);
+	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 = kmalloc(sizeof(*head_ref), 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);
+
+	if (waitqueue_active(&delayed_refs->seq_wait))
+		wake_up(&delayed_refs->seq_wait);
+	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_node *ref;
+	struct btrfs_delayed_ref_root *delayed_refs;
+
+	delayed_refs = &trans->transaction->delayed_refs;
+	ref = find_ref_head(&delayed_refs->root, bytenr, NULL, 0);
+	if (ref)
+		return btrfs_delayed_node_to_head(ref);
+	return NULL;
+}