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-rw-r--r--fs/btrfs/delayed-ref.c668
1 files changed, 668 insertions, 0 deletions
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
new file mode 100644
index 000000000000..d6c01c096a40
--- /dev/null
+++ b/fs/btrfs/delayed-ref.c
@@ -0,0 +1,668 @@
+/*
+ * 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/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.
+ *
+ * Right now this code is only used for reference counted trees, but
+ * the long term goal is to get rid of the similar code for delayed
+ * extent tree modifications.
+ */
+
+/*
+ * entries in the rb tree are ordered by the byte number of the extent
+ * and by the byte number of the parent block.
+ */
+static int comp_entry(struct btrfs_delayed_ref_node *ref,
+ u64 bytenr, u64 parent)
+{
+ if (bytenr < ref->bytenr)
+ return -1;
+ if (bytenr > ref->bytenr)
+ return 1;
+ if (parent < ref->parent)
+ return -1;
+ if (parent > ref->parent)
+ return 1;
+ 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,
+ u64 bytenr, u64 parent,
+ struct rb_node *node)
+{
+ struct rb_node **p = &root->rb_node;
+ struct rb_node *parent_node = NULL;
+ struct btrfs_delayed_ref_node *entry;
+ int cmp;
+
+ while (*p) {
+ parent_node = *p;
+ entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
+ rb_node);
+
+ cmp = comp_entry(entry, bytenr, parent);
+ if (cmp < 0)
+ p = &(*p)->rb_left;
+ else if (cmp > 0)
+ p = &(*p)->rb_right;
+ else
+ return entry;
+ }
+
+ entry = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
+ rb_link_node(node, parent_node, p);
+ rb_insert_color(node, root);
+ return NULL;
+}
+
+/*
+ * find an entry based on (bytenr,parent). This returns the delayed
+ * ref if it was able to find one, or NULL if nothing was in that spot
+ */
+static struct btrfs_delayed_ref_node *tree_search(struct rb_root *root,
+ u64 bytenr, u64 parent,
+ struct btrfs_delayed_ref_node **last)
+{
+ struct rb_node *n = root->rb_node;
+ struct btrfs_delayed_ref_node *entry;
+ int cmp;
+
+ while (n) {
+ entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
+ WARN_ON(!entry->in_tree);
+ if (last)
+ *last = entry;
+
+ cmp = comp_entry(entry, bytenr, parent);
+ if (cmp < 0)
+ n = n->rb_left;
+ else if (cmp > 0)
+ n = n->rb_right;
+ else
+ 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_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;
+ tree_search(&delayed_refs->root, start, (u64)-1, &ref);
+ if (ref) {
+ struct btrfs_delayed_ref_node *tmp;
+
+ node = rb_prev(&ref->rb_node);
+ while (node) {
+ tmp = rb_entry(node,
+ struct btrfs_delayed_ref_node,
+ rb_node);
+ if (tmp->bytenr < start)
+ break;
+ ref = tmp;
+ node = rb_prev(&ref->rb_node);
+ }
+ 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;
+}
+
+/*
+ * This checks to see if there are any delayed refs in the
+ * btree for a given bytenr. It returns one if it finds any
+ * and zero otherwise.
+ *
+ * If it only finds a head node, it returns 0.
+ *
+ * The idea is to use this when deciding if you can safely delete an
+ * extent from the extent allocation tree. There may be a pending
+ * ref in the rbtree that adds or removes references, so as long as this
+ * returns one you need to leave the BTRFS_EXTENT_ITEM in the extent
+ * allocation tree.
+ */
+int btrfs_delayed_ref_pending(struct btrfs_trans_handle *trans, u64 bytenr)
+{
+ struct btrfs_delayed_ref_node *ref;
+ struct btrfs_delayed_ref_root *delayed_refs;
+ struct rb_node *prev_node;
+ int ret = 0;
+
+ delayed_refs = &trans->transaction->delayed_refs;
+ spin_lock(&delayed_refs->lock);
+
+ ref = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
+ if (ref) {
+ prev_node = rb_prev(&ref->rb_node);
+ if (!prev_node)
+ goto out;
+ ref = rb_entry(prev_node, struct btrfs_delayed_ref_node,
+ rb_node);
+ if (ref->bytenr == bytenr)
+ ret = 1;
+ }
+out:
+ spin_unlock(&delayed_refs->lock);
+ return ret;
+}
+
+/*
+ * helper function to lookup reference count
+ *
+ * the head node for delayed ref is used to store the sum of all the
+ * reference count modifications queued up in the rbtree. This way you
+ * can check to see what the reference count would be if all of the
+ * delayed refs are processed.
+ */
+int btrfs_lookup_extent_ref(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, u64 bytenr,
+ u64 num_bytes, u32 *refs)
+{
+ struct btrfs_delayed_ref_node *ref;
+ struct btrfs_delayed_ref_head *head;
+ struct btrfs_delayed_ref_root *delayed_refs;
+ struct btrfs_path *path;
+ struct extent_buffer *leaf;
+ struct btrfs_extent_item *ei;
+ struct btrfs_key key;
+ u32 num_refs;
+ int ret;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ key.objectid = bytenr;
+ key.type = BTRFS_EXTENT_ITEM_KEY;
+ key.offset = num_bytes;
+ delayed_refs = &trans->transaction->delayed_refs;
+again:
+ ret = btrfs_search_slot(trans, root->fs_info->extent_root,
+ &key, path, 0, 0);
+ if (ret < 0)
+ goto out;
+
+ if (ret == 0) {
+ leaf = path->nodes[0];
+ ei = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_extent_item);
+ num_refs = btrfs_extent_refs(leaf, ei);
+ } else {
+ num_refs = 0;
+ ret = 0;
+ }
+
+ spin_lock(&delayed_refs->lock);
+ ref = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
+ if (ref) {
+ head = btrfs_delayed_node_to_head(ref);
+ if (mutex_trylock(&head->mutex)) {
+ num_refs += ref->ref_mod;
+ mutex_unlock(&head->mutex);
+ *refs = num_refs;
+ goto out;
+ }
+
+ atomic_inc(&ref->refs);
+ spin_unlock(&delayed_refs->lock);
+
+ btrfs_release_path(root->fs_info->extent_root, path);
+
+ mutex_lock(&head->mutex);
+ mutex_unlock(&head->mutex);
+ btrfs_put_delayed_ref(ref);
+ goto again;
+ } else {
+ *refs = num_refs;
+ }
+out:
+ spin_unlock(&delayed_refs->lock);
+ btrfs_free_path(path);
+ return ret;
+}
+
+/*
+ * 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)
+{
+ struct btrfs_delayed_ref *existing_ref;
+ struct btrfs_delayed_ref *ref;
+
+ existing_ref = btrfs_delayed_node_to_ref(existing);
+ ref = btrfs_delayed_node_to_ref(update);
+
+ if (ref->pin)
+ existing_ref->pin = 1;
+
+ if (ref->action != existing_ref->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 {
+ if (existing_ref->action == BTRFS_ADD_DELAYED_REF) {
+ /* if we're adding refs, make sure all the
+ * details match up. The extent could
+ * have been totally freed and reallocated
+ * by a different owner before the delayed
+ * ref entries were removed.
+ */
+ existing_ref->owner_objectid = ref->owner_objectid;
+ existing_ref->generation = ref->generation;
+ existing_ref->root = ref->root;
+ existing->num_bytes = update->num_bytes;
+ }
+ /*
+ * 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);
+
+ 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;
+
+ }
+
+ /*
+ * update the reference mod on the head to reflect this new operation
+ */
+ existing->ref_mod += update->ref_mod;
+}
+
+/*
+ * helper function to actually insert a delayed ref into the rbtree.
+ * this does all the dirty work in terms of maintaining the correct
+ * overall modification count in the head node and properly dealing
+ * with updating existing nodes as new modifications are queued.
+ */
+static noinline int __btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
+ struct btrfs_delayed_ref_node *ref,
+ u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
+ u64 ref_generation, u64 owner_objectid, int action,
+ int pin)
+{
+ struct btrfs_delayed_ref_node *existing;
+ struct btrfs_delayed_ref *full_ref;
+ 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 (parent == (u64)-1) {
+ if (action == BTRFS_DROP_DELAYED_REF)
+ count_mod = -1;
+ else if (action == BTRFS_UPDATE_DELAYED_HEAD)
+ count_mod = 0;
+ }
+
+ /*
+ * 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;
+ action = BTRFS_ADD_DELAYED_REF;
+ } 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->parent = parent;
+ ref->ref_mod = count_mod;
+ ref->in_tree = 1;
+ ref->num_bytes = num_bytes;
+
+ if (btrfs_delayed_ref_is_head(ref)) {
+ head_ref = btrfs_delayed_node_to_head(ref);
+ head_ref->must_insert_reserved = must_insert_reserved;
+ INIT_LIST_HEAD(&head_ref->cluster);
+ mutex_init(&head_ref->mutex);
+ } else {
+ full_ref = btrfs_delayed_node_to_ref(ref);
+ full_ref->root = ref_root;
+ full_ref->generation = ref_generation;
+ full_ref->owner_objectid = owner_objectid;
+ full_ref->pin = pin;
+ full_ref->action = action;
+ }
+
+ existing = tree_insert(&delayed_refs->root, bytenr,
+ parent, &ref->rb_node);
+
+ if (existing) {
+ if (btrfs_delayed_ref_is_head(ref))
+ update_existing_head_ref(existing, ref);
+ else
+ update_existing_ref(trans, delayed_refs, existing, ref);
+
+ /*
+ * we've updated the existing ref, free the newly
+ * allocated ref
+ */
+ kfree(ref);
+ } else {
+ if (btrfs_delayed_ref_is_head(ref)) {
+ delayed_refs->num_heads++;
+ delayed_refs->num_heads_ready++;
+ }
+ delayed_refs->num_entries++;
+ trans->delayed_ref_updates++;
+ }
+ return 0;
+}
+
+/*
+ * add a delayed ref to the tree. This does all of the accounting required
+ * to make sure the delayed ref is eventually processed before this
+ * transaction commits.
+ */
+int btrfs_add_delayed_ref(struct btrfs_trans_handle *trans,
+ u64 bytenr, u64 num_bytes, u64 parent, u64 ref_root,
+ u64 ref_generation, u64 owner_objectid, int action,
+ int pin)
+{
+ struct btrfs_delayed_ref *ref;
+ struct btrfs_delayed_ref_head *head_ref;
+ struct btrfs_delayed_ref_root *delayed_refs;
+ int ret;
+
+ ref = kmalloc(sizeof(*ref), GFP_NOFS);
+ if (!ref)
+ return -ENOMEM;
+
+ /*
+ * the parent = 0 case comes from cases where we don't actually
+ * know the parent yet. It will get updated later via a add/drop
+ * pair.
+ */
+ if (parent == 0)
+ parent = bytenr;
+
+ head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
+ if (!head_ref) {
+ kfree(ref);
+ return -ENOMEM;
+ }
+ 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
+ */
+ ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
+ (u64)-1, 0, 0, 0, action, pin);
+ BUG_ON(ret);
+
+ ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
+ parent, ref_root, ref_generation,
+ owner_objectid, action, pin);
+ BUG_ON(ret);
+ 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 = tree_search(&delayed_refs->root, bytenr, (u64)-1, NULL);
+ if (ref)
+ return btrfs_delayed_node_to_head(ref);
+ return NULL;
+}
+
+/*
+ * add a delayed ref to the tree. This does all of the accounting required
+ * to make sure the delayed ref is eventually processed before this
+ * transaction commits.
+ *
+ * The main point of this call is to add and remove a backreference in a single
+ * shot, taking the lock only once, and only searching for the head node once.
+ *
+ * It is the same as doing a ref add and delete in two separate calls.
+ */
+int btrfs_update_delayed_ref(struct btrfs_trans_handle *trans,
+ u64 bytenr, u64 num_bytes, u64 orig_parent,
+ u64 parent, u64 orig_ref_root, u64 ref_root,
+ u64 orig_ref_generation, u64 ref_generation,
+ u64 owner_objectid, int pin)
+{
+ struct btrfs_delayed_ref *ref;
+ struct btrfs_delayed_ref *old_ref;
+ struct btrfs_delayed_ref_head *head_ref;
+ struct btrfs_delayed_ref_root *delayed_refs;
+ int ret;
+
+ ref = kmalloc(sizeof(*ref), GFP_NOFS);
+ if (!ref)
+ return -ENOMEM;
+
+ old_ref = kmalloc(sizeof(*old_ref), GFP_NOFS);
+ if (!old_ref) {
+ kfree(ref);
+ return -ENOMEM;
+ }
+
+ /*
+ * the parent = 0 case comes from cases where we don't actually
+ * know the parent yet. It will get updated later via a add/drop
+ * pair.
+ */
+ if (parent == 0)
+ parent = bytenr;
+ if (orig_parent == 0)
+ orig_parent = bytenr;
+
+ head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
+ if (!head_ref) {
+ kfree(ref);
+ kfree(old_ref);
+ return -ENOMEM;
+ }
+ 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
+ */
+ ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
+ (u64)-1, 0, 0, 0,
+ BTRFS_UPDATE_DELAYED_HEAD, 0);
+ BUG_ON(ret);
+
+ ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
+ parent, ref_root, ref_generation,
+ owner_objectid, BTRFS_ADD_DELAYED_REF, 0);
+ BUG_ON(ret);
+
+ ret = __btrfs_add_delayed_ref(trans, &old_ref->node, bytenr, num_bytes,
+ orig_parent, orig_ref_root,
+ orig_ref_generation, owner_objectid,
+ BTRFS_DROP_DELAYED_REF, pin);
+ BUG_ON(ret);
+ spin_unlock(&delayed_refs->lock);
+ return 0;
+}