1 files changed, 164 insertions, 88 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 41a63462d3eb..7e40c516fe62 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -25,6 +25,7 @@
 #include "print-tree.h"
 #include "transaction.h"
 #include "volumes.h"
+#include "locking.h"
 
 #define BLOCK_GROUP_DATA     EXTENT_WRITEBACK
 #define BLOCK_GROUP_METADATA EXTENT_UPTODATE
@@ -36,7 +37,28 @@ static int finish_current_insert(struct btrfs_trans_handle *trans, struct
                                  btrfs_root *extent_root);
 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
                                btrfs_root *extent_root);
+static struct btrfs_block_group_cache *
+__btrfs_find_block_group(struct btrfs_root *root,
+                         struct btrfs_block_group_cache *hint,
+                         u64 search_start, int data, int owner);
 
+void maybe_lock_mutex(struct btrfs_root *root)
+{
+        if (root != root->fs_info->extent_root &&
+            root != root->fs_info->chunk_root &&
+            root != root->fs_info->dev_root) {
+                mutex_lock(&root->fs_info->alloc_mutex);
+        }
+}
+
+void maybe_unlock_mutex(struct btrfs_root *root)
+{
+        if (root != root->fs_info->extent_root &&
+            root != root->fs_info->chunk_root &&
+            root != root->fs_info->dev_root) {
+                mutex_unlock(&root->fs_info->alloc_mutex);
+        }
+}
 
 static int cache_block_group(struct btrfs_root *root,
                              struct btrfs_block_group_cache *block_group)
@@ -66,6 +88,7 @@ static int cache_block_group(struct btrfs_root *root,
                 return -ENOMEM;
 
         path->reada = 2;
+        path->skip_locking = 1;
         first_free = block_group->key.objectid;
         key.objectid = block_group->key.objectid;
         key.offset = 0;
@@ -290,7 +313,7 @@ no_cache:
                 cache = btrfs_lookup_first_block_group(root->fs_info, last);
         }
         cache_miss = 0;
-        cache = btrfs_find_block_group(root, cache, last, data, 0);
+        cache = __btrfs_find_block_group(root, cache, last, data, 0);
         if (!cache)
                 goto no_cache;
         *cache_ret = cache;
@@ -318,10 +341,10 @@ static int block_group_state_bits(u64 flags)
         return bits;
 }
 
-struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
-                                                 struct btrfs_block_group_cache
-                                                 *hint, u64 search_start,
-                                                 int data, int owner)
+static struct btrfs_block_group_cache *
+__btrfs_find_block_group(struct btrfs_root *root,
+                         struct btrfs_block_group_cache *hint,
+                         u64 search_start, int data, int owner)
 {
         struct btrfs_block_group_cache *cache;
         struct extent_io_tree *block_group_cache;
@@ -411,6 +434,18 @@ found:
         return found_group;
 }
 
+struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
+                                                 struct btrfs_block_group_cache
+                                                 *hint, u64 search_start,
+                                                 int data, int owner)
+{
+
+        struct btrfs_block_group_cache *ret;
+        mutex_lock(&root->fs_info->alloc_mutex);
+        ret = __btrfs_find_block_group(root, hint, search_start, data, owner);
+        mutex_unlock(&root->fs_info->alloc_mutex);
+        return ret;
+}
 static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
                            u64 owner, u64 owner_offset)
 {
@@ -646,7 +681,7 @@ out:
         return ret;
 }
 
-int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
+static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 u64 bytenr, u64 num_bytes,
                                 u64 root_objectid, u64 ref_generation,
@@ -696,6 +731,22 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
         return 0;
 }
 
+int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
+                                struct btrfs_root *root,
+                                u64 bytenr, u64 num_bytes,
+                                u64 root_objectid, u64 ref_generation,
+                                u64 owner, u64 owner_offset)
+{
+        int ret;
+
+        mutex_lock(&root->fs_info->alloc_mutex);
+        ret = __btrfs_inc_extent_ref(trans, root, bytenr, num_bytes,
+                                     root_objectid, ref_generation,
+                                     owner, owner_offset);
+        mutex_unlock(&root->fs_info->alloc_mutex);
+        return ret;
+}
+
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root)
 {
@@ -760,6 +811,10 @@ u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
         struct btrfs_extent_ref *ref_item;
         int level = -1;
 
+        /* FIXME, needs locking */
+        BUG();
+
+        mutex_lock(&root->fs_info->alloc_mutex);
         path = btrfs_alloc_path();
 again:
         if (level == -1)
@@ -854,33 +909,9 @@ again:
 
 out:
         btrfs_free_path(path);
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return total_count;
 }
-int btrfs_inc_root_ref(struct btrfs_trans_handle *trans,
-                       struct btrfs_root *root, u64 owner_objectid)
-{
-        u64 generation;
-        u64 key_objectid;
-        u64 level;
-        u32 nritems;
-        struct btrfs_disk_key disk_key;
-
-        level = btrfs_header_level(root->node);
-        generation = trans->transid;
-        nritems = btrfs_header_nritems(root->node);
-        if (nritems > 0) {
-                if (level == 0)
-                        btrfs_item_key(root->node, &disk_key, 0);
-                else
-                        btrfs_node_key(root->node, &disk_key, 0);
-                key_objectid = btrfs_disk_key_objectid(&disk_key);
-        } else {
-                key_objectid = 0;
-        }
-        return btrfs_inc_extent_ref(trans, root, root->node->start,
-                                    root->node->len, owner_objectid,
-                                    generation, level, key_objectid);
-}
 
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct extent_buffer *buf)
@@ -897,6 +928,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
         if (!root->ref_cows)
                 return 0;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
         level = btrfs_header_level(buf);
         nritems = btrfs_header_nritems(buf);
         for (i = 0; i < nritems; i++) {
@@ -913,7 +945,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                         disk_bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
                         if (disk_bytenr == 0)
                                 continue;
-                        ret = btrfs_inc_extent_ref(trans, root, disk_bytenr,
+                        ret = __btrfs_inc_extent_ref(trans, root, disk_bytenr,
                                     btrfs_file_extent_disk_num_bytes(buf, fi),
                                     root->root_key.objectid, trans->transid,
                                     key.objectid, key.offset);
@@ -924,7 +956,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 } else {
                         bytenr = btrfs_node_blockptr(buf, i);
                         btrfs_node_key_to_cpu(buf, &key, i);
-                        ret = btrfs_inc_extent_ref(trans, root, bytenr,
+                        ret = __btrfs_inc_extent_ref(trans, root, bytenr,
                                            btrfs_level_size(root, level - 1),
                                            root->root_key.objectid,
                                            trans->transid,
@@ -935,6 +967,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                         }
                 }
         }
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return 0;
 fail:
         WARN_ON(1);
@@ -965,6 +998,7 @@ fail:
                 }
         }
 #endif
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return ret;
 }
 
@@ -1019,6 +1053,7 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
         if (!path)
                 return -ENOMEM;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
         while(1) {
                 ret = find_first_extent_bit(block_group_cache, last,
                                             &start, &end, BLOCK_GROUP_DIRTY);
@@ -1045,6 +1080,7 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                   BLOCK_GROUP_DIRTY, GFP_NOFS);
         }
         btrfs_free_path(path);
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return werr;
 }
 
@@ -1162,26 +1198,28 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                 space_info->force_alloc = 0;
         }
         if (space_info->full)
-                return 0;
+                goto out;
 
         thresh = div_factor(space_info->total_bytes, 6);
         if (!force &&
            (space_info->bytes_used + space_info->bytes_pinned + alloc_bytes) <
             thresh)
-                return 0;
+                goto out;
 
+        mutex_lock(&extent_root->fs_info->chunk_mutex);
         ret = btrfs_alloc_chunk(trans, extent_root, &start, &num_bytes, flags);
         if (ret == -ENOSPC) {
 printk("space info full %Lu\n", flags);
                 space_info->full = 1;
-                return 0;
+                goto out;
         }
         BUG_ON(ret);
 
         ret = btrfs_make_block_group(trans, extent_root, 0, flags,
                      BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);
         BUG_ON(ret);
-
+        mutex_unlock(&extent_root->fs_info->chunk_mutex);
+out:
         return 0;
 }
 
@@ -1318,6 +1356,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
         struct extent_io_tree *free_space_cache;
         free_space_cache = &root->fs_info->free_space_cache;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
         while(1) {
                 ret = find_first_extent_bit(unpin, 0, &start, &end,
                                             EXTENT_DIRTY);
@@ -1327,6 +1366,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                 clear_extent_dirty(unpin, start, end, GFP_NOFS);
                 set_extent_dirty(free_space_cache, start, end, GFP_NOFS);
         }
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return 0;
 }
 
@@ -1363,18 +1403,24 @@ static int finish_current_insert(struct btrfs_trans_handle *trans,
                                   GFP_NOFS);
                 eb = read_tree_block(extent_root, ins.objectid, ins.offset,
                                      trans->transid);
+                btrfs_tree_lock(eb);
                 level = btrfs_header_level(eb);
                 if (level == 0) {
                         btrfs_item_key(eb, &first, 0);
                 } else {
                         btrfs_node_key(eb, &first, 0);
                 }
+                btrfs_tree_unlock(eb);
+                free_extent_buffer(eb);
+                /*
+                 * the first key is just a hint, so the race we've created
+                 * against reading it is fine
+                 */
                 err = btrfs_insert_extent_backref(trans, extent_root, path,
                                           start, extent_root->root_key.objectid,
                                           0, level,
                                           btrfs_disk_key_objectid(&first));
                 BUG_ON(err);
-                free_extent_buffer(eb);
         }
         btrfs_free_path(path);
         return 0;
@@ -1384,12 +1430,14 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
                           int pending)
 {
         int err = 0;
-        struct extent_buffer *buf;
 
         if (!pending) {
+#if 0
+                struct extent_buffer *buf;
                 buf = btrfs_find_tree_block(root, bytenr, num_bytes);
                 if (buf) {
-                        if (btrfs_buffer_uptodate(buf, 0)) {
+                        if (!btrfs_try_tree_lock(buf) &&
+                            btrfs_buffer_uptodate(buf, 0)) {
                                 u64 transid =
                                     root->fs_info->running_transaction->transid;
                                 u64 header_transid =
@@ -1398,12 +1446,15 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
                                     !btrfs_header_flag(buf,
                                                BTRFS_HEADER_FLAG_WRITTEN)) {
                                         clean_tree_block(NULL, root, buf);
+                                        btrfs_tree_unlock(buf);
                                         free_extent_buffer(buf);
                                         return 1;
                                 }
+                                btrfs_tree_unlock(buf);
                         }
                         free_extent_buffer(buf);
                 }
+#endif
                 update_pinned_extents(root, bytenr, num_bytes, 1);
         } else {
                 set_extent_bits(&root->fs_info->pending_del,
@@ -1586,10 +1637,11 @@ static int del_pending_extents(struct btrfs_trans_handle *trans, struct
 /*
  * remove an extent from the root, returns 0 on success
  */
-int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-                      *root, u64 bytenr, u64 num_bytes,
-                      u64 root_objectid, u64 ref_generation,
-                      u64 owner_objectid, u64 owner_offset, int pin)
+static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
+                               struct btrfs_root *root, u64 bytenr,
+                               u64 num_bytes, u64 root_objectid,
+                               u64 ref_generation, u64 owner_objectid,
+                               u64 owner_offset, int pin)
 {
         struct btrfs_root *extent_root = root->fs_info->extent_root;
         int pending_ret;
@@ -1610,6 +1662,22 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
         return ret ? ret : pending_ret;
 }
 
+int btrfs_free_extent(struct btrfs_trans_handle *trans,
+                      struct btrfs_root *root, u64 bytenr,
+                      u64 num_bytes, u64 root_objectid,
+                      u64 ref_generation, u64 owner_objectid,
+                      u64 owner_offset, int pin)
+{
+        int ret;
+
+        maybe_lock_mutex(root);
+        ret = __btrfs_free_extent(trans, root, bytenr, num_bytes,
+                                  root_objectid, ref_generation,
+                                  owner_objectid, owner_offset, pin);
+        maybe_unlock_mutex(root);
+        return ret;
+}
+
 static u64 stripe_align(struct btrfs_root *root, u64 val)
 {
         u64 mask = ((u64)root->stripesize - 1);
@@ -1679,12 +1747,12 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                 block_group = btrfs_lookup_first_block_group(info, hint_byte);
                 if (!block_group)
                         hint_byte = search_start;
-                block_group = btrfs_find_block_group(root, block_group,
+                block_group = __btrfs_find_block_group(root, block_group,
                                                      hint_byte, data, 1);
                 if (last_ptr && *last_ptr == 0 && block_group)
                         hint_byte = block_group->key.objectid;
         } else {
-                block_group = btrfs_find_block_group(root,
+                block_group = __btrfs_find_block_group(root,
                                                      trans->block_group,
                                                      search_start, data, 1);
         }
@@ -1806,7 +1874,7 @@ enospc:
         }
         block_group = btrfs_lookup_first_block_group(info, search_start);
         cond_resched();
-        block_group = btrfs_find_block_group(root, block_group,
+        block_group = __btrfs_find_block_group(root, block_group,
                                              search_start, data, 0);
         goto check_failed;
 
@@ -1843,6 +1911,8 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
         struct btrfs_path *path;
         struct btrfs_key keys[2];
 
+        maybe_lock_mutex(root);
+
         if (data) {
                 alloc_profile = info->avail_data_alloc_bits &
                                 info->data_alloc_profile;
@@ -1892,9 +1962,10 @@ again:
         if (ret) {
                 printk("allocation failed flags %Lu\n", data);
         }
-        BUG_ON(ret);
-        if (ret)
-                return ret;
+        if (ret) {
+                BUG();
+                goto out;
+        }
 
         /* block accounting for super block */
         super_used = btrfs_super_bytes_used(&info->super_copy);
@@ -1953,11 +2024,11 @@ again:
         finish_current_insert(trans, extent_root);
         pending_ret = del_pending_extents(trans, extent_root);
 
-        if (ret) {
-                return ret;
-        }
+        if (ret)
+                goto out;
         if (pending_ret) {
-                return pending_ret;
+                ret = pending_ret;
+                goto out;
         }
 
 update_block:
@@ -1967,9 +2038,10 @@ update_block:
                        ins->objectid, ins->offset);
                 BUG();
         }
-        return 0;
+out:
+        maybe_unlock_mutex(root);
+        return ret;
 }
-
 /*
  * helper function to allocate a block for a given tree
  * returns the tree buffer or NULL.
@@ -1977,28 +2049,6 @@ update_block:
 struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                              struct btrfs_root *root,
                                              u32 blocksize,
-                                             u64 root_objectid, u64 hint,
-                                             u64 empty_size)
-{
-        u64 ref_generation;
-
-        if (root->ref_cows)
-                ref_generation = trans->transid;
-        else
-                ref_generation = 0;
-
-
-        return __btrfs_alloc_free_block(trans, root, blocksize, root_objectid,
-                                        ref_generation, 0, 0, hint, empty_size);
-}
-
-/*
- * helper function to allocate a block for a given tree
- * returns the tree buffer or NULL.
- */
-struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
-                                             struct btrfs_root *root,
-                                             u32 blocksize,
                                              u64 root_objectid,
                                              u64 ref_generation,
                                              u64 first_objectid,
@@ -2026,6 +2076,7 @@ struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                 return ERR_PTR(-ENOMEM);
         }
         btrfs_set_header_generation(buf, trans->transid);
+        btrfs_tree_lock(buf);
         clean_tree_block(trans, root, buf);
         btrfs_set_buffer_uptodate(buf);
 
@@ -2076,7 +2127,7 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
                 disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                 if (disk_bytenr == 0)
                         continue;
-                ret = btrfs_free_extent(trans, root, disk_bytenr,
+                ret = __btrfs_free_extent(trans, root, disk_bytenr,
                                 btrfs_file_extent_disk_num_bytes(leaf, fi),
                                 leaf_owner, leaf_generation,
                                 key.objectid, key.offset, 0);
@@ -2151,6 +2202,8 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
         int ret;
         u32 refs;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
+
         WARN_ON(*level < 0);
         WARN_ON(*level >= BTRFS_MAX_LEVEL);
         ret = lookup_extent_ref(trans, root,
@@ -2182,6 +2235,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                 bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                 ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
                 blocksize = btrfs_level_size(root, *level - 1);
+
                 ret = lookup_extent_ref(trans, root, bytenr, blocksize, &refs);
                 BUG_ON(ret);
                 if (refs != 1) {
@@ -2189,7 +2243,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                         root_owner = btrfs_header_owner(parent);
                         root_gen = btrfs_header_generation(parent);
                         path->slots[*level]++;
-                        ret = btrfs_free_extent(trans, root, bytenr,
+                        ret = __btrfs_free_extent(trans, root, bytenr,
                                                 blocksize, root_owner,
                                                 root_gen, 0, 0, 1);
                         BUG_ON(ret);
@@ -2201,9 +2255,11 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                         reada_walk_down(root, cur, path->slots[*level]);
 
                         mutex_unlock(&root->fs_info->fs_mutex);
+                        mutex_unlock(&root->fs_info->alloc_mutex);
                         next = read_tree_block(root, bytenr, blocksize,
                                                ptr_gen);
                         mutex_lock(&root->fs_info->fs_mutex);
+                        mutex_lock(&root->fs_info->alloc_mutex);
 
                         /* we've dropped the lock, double check */
                         ret = lookup_extent_ref(trans, root, bytenr,
@@ -2216,7 +2272,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 
                                 path->slots[*level]++;
                                 free_extent_buffer(next);
-                                ret = btrfs_free_extent(trans, root, bytenr,
+                                ret = __btrfs_free_extent(trans, root, bytenr,
                                                         blocksize,
                                                         root_owner,
                                                         root_gen, 0, 0, 1);
@@ -2244,13 +2300,14 @@ out:
         }
 
         root_gen = btrfs_header_generation(parent);
-        ret = btrfs_free_extent(trans, root, path->nodes[*level]->start,
+        ret = __btrfs_free_extent(trans, root, path->nodes[*level]->start,
                                 path->nodes[*level]->len,
                                 root_owner, root_gen, 0, 0, 1);
         free_extent_buffer(path->nodes[*level]);
         path->nodes[*level] = NULL;
         *level += 1;
         BUG_ON(ret);
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return 0;
 }
 
@@ -2350,6 +2407,12 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                 btrfs_node_key(node, &found_key, path->slots[level]);
                 WARN_ON(memcmp(&found_key, &root_item->drop_progress,
                                sizeof(found_key)));
+                for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
+                        if (path->nodes[i] && path->locks[i]) {
+                                path->locks[i] = 0;
+                                btrfs_tree_unlock(path->nodes[i]);
+                        }
+                }
         }
         while(1) {
                 wret = walk_down_tree(trans, root, path, &level);
@@ -2383,6 +2446,8 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
         u64 end;
         u64 ptr;
         int ret;
+
+        mutex_lock(&info->alloc_mutex);
         while(1) {
                 ret = find_first_extent_bit(&info->block_group_cache, 0,
                                             &start, &end, (unsigned int)-1);
@@ -2402,6 +2467,7 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
                 clear_extent_dirty(&info->free_space_cache, start,
                                    end, GFP_NOFS);
         }
+        mutex_unlock(&info->alloc_mutex);
         return 0;
 }
 
@@ -2678,6 +2744,7 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
 
                 eb = read_tree_block(found_root, extent_key->objectid,
                                      extent_key->offset, 0);
+                btrfs_tree_lock(eb);
                 level = btrfs_header_level(eb);
 
                 if (level == 0)
@@ -2685,6 +2752,7 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                 else
                         btrfs_node_key_to_cpu(eb, &found_key, 0);
 
+                btrfs_tree_unlock(eb);
                 free_extent_buffer(eb);
 
                 ret = find_root_for_ref(extent_root, path, &found_key,
@@ -2888,6 +2956,7 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
         int ret;
         int progress;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
         shrink_block_group = btrfs_lookup_block_group(root->fs_info,
                                                       shrink_start);
         BUG_ON(!shrink_block_group);
@@ -3044,20 +3113,22 @@ next:
                            (unsigned int)-1, GFP_NOFS);
 out:
         btrfs_free_path(path);
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return ret;
 }
 
 int find_first_block_group(struct btrfs_root *root, struct btrfs_path *path,
                            struct btrfs_key *key)
 {
-        int ret;
+        int ret = 0;
         struct btrfs_key found_key;
         struct extent_buffer *leaf;
         int slot;
 
         ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
         if (ret < 0)
-                return ret;
+                goto out;
+
         while(1) {
                 slot = path->slots[0];
                 leaf = path->nodes[0];
@@ -3066,18 +3137,20 @@ int find_first_block_group(struct btrfs_root *root, struct btrfs_path *path,
                         if (ret == 0)
                                 continue;
                         if (ret < 0)
-                                goto error;
+                                goto out;
                         break;
                 }
                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 
                 if (found_key.objectid >= key->objectid &&
-                    found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY)
-                        return 0;
+                    found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
+                        ret = 0;
+                        goto out;
+                }
                 path->slots[0]++;
         }
         ret = -ENOENT;
-error:
+out:
         return ret;
 }
 
@@ -3103,6 +3176,7 @@ int btrfs_read_block_groups(struct btrfs_root *root)
         if (!path)
                 return -ENOMEM;
 
+        mutex_lock(&root->fs_info->alloc_mutex);
         while(1) {
                 ret = find_first_block_group(root, path, &key);
                 if (ret > 0) {
@@ -3158,6 +3232,7 @@ int btrfs_read_block_groups(struct btrfs_root *root)
         ret = 0;
 error:
         btrfs_free_path(path);
+        mutex_unlock(&root->fs_info->alloc_mutex);
         return ret;
 }
 
@@ -3205,5 +3280,6 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
         ret = del_pending_extents(trans, extent_root);
         BUG_ON(ret);
         set_avail_alloc_bits(extent_root->fs_info, type);
+
         return 0;
 }