1 files changed, 585 insertions, 0 deletions

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
new file mode 100644
index 000000000000..874565a1f634
--- /dev/null
+++ b/fs/btrfs/delayed-ref.c
@@ -0,0 +1,585 @@
+/*
+ * 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 <linux/ftrace.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 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);
+
+                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;
+}
+
+/*
+ * Locking on delayed refs is done by taking a lock on the head node,
+ * which has the (impossible) parent id of (u64)-1.  Once a lock is held
+ * on the head node, you're allowed (and required) to process all the
+ * delayed refs for a given byte number in the tree.
+ *
+ * This will walk forward in the rbtree until it finds a head node it
+ * is able to lock.  It might not lock the delayed ref you asked for,
+ * and so it will return the one it did lock in next_ret and return 0.
+ *
+ * If no locks are taken, next_ret is set to null and 1 is returned.  This
+ * means there are no more unlocked head nodes in the rbtree.
+ */
+int btrfs_lock_delayed_ref(struct btrfs_trans_handle *trans,
+                           struct btrfs_delayed_ref_node *ref,
+                           struct btrfs_delayed_ref_head **next_ret)
+{
+        struct rb_node *node;
+        struct btrfs_delayed_ref_head *head;
+        int ret = 0;
+
+        while (1) {
+                if (btrfs_delayed_ref_is_head(ref)) {
+                        head = btrfs_delayed_node_to_head(ref);
+                        if (mutex_trylock(&head->mutex)) {
+                                *next_ret = head;
+                                ret = 0;
+                                break;
+                        }
+                }
+                node = rb_next(&ref->rb_node);
+                if (!node) {
+                        ret = 1;
+                        *next_ret = NULL;
+                        break;
+                }
+                ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
+        }
+        return ret;
+}
+
+/*
+ * 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);
+        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);
+        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;
+        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 && 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;
+                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;
+                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 {
+                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;
+}
+
+/*
+ * 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_ADD_DELAYED_REF, 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;
+}