Btrfs: Add locking around volume management (device add/remove/balance)
[deliverable/linux.git] / fs / btrfs / extent-tree.c
index df95fb660d4904f3ff38a9d642204ffb2c61966b..8ebfa6be079017fed9608f114c8ed7fcede27b17 100644 (file)
@@ -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 +88,12 @@ static int cache_block_group(struct btrfs_root *root,
                return -ENOMEM;
 
        path->reada = 2;
+       /*
+        * we get into deadlocks with paths held by callers of this function.
+        * since the alloc_mutex is protecting things right now, just
+        * skip the locking here
+        */
+       path->skip_locking = 1;
        first_free = block_group->key.objectid;
        key.objectid = block_group->key.objectid;
        key.offset = 0;
@@ -136,6 +164,35 @@ err:
        return 0;
 }
 
+struct btrfs_block_group_cache *btrfs_lookup_first_block_group(struct
+                                                      btrfs_fs_info *info,
+                                                        u64 bytenr)
+{
+       struct extent_io_tree *block_group_cache;
+       struct btrfs_block_group_cache *block_group = NULL;
+       u64 ptr;
+       u64 start;
+       u64 end;
+       int ret;
+
+       bytenr = max_t(u64, bytenr,
+                      BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE);
+       block_group_cache = &info->block_group_cache;
+       ret = find_first_extent_bit(block_group_cache,
+                                   bytenr, &start, &end,
+                                   BLOCK_GROUP_DATA | BLOCK_GROUP_METADATA |
+                                   BLOCK_GROUP_SYSTEM);
+       if (ret) {
+               return NULL;
+       }
+       ret = get_state_private(block_group_cache, start, &ptr);
+       if (ret)
+               return NULL;
+
+       block_group = (struct btrfs_block_group_cache *)(unsigned long)ptr;
+       return block_group;
+}
+
 struct btrfs_block_group_cache *btrfs_lookup_block_group(struct
                                                         btrfs_fs_info *info,
                                                         u64 bytenr)
@@ -175,7 +232,7 @@ static int block_group_bits(struct btrfs_block_group_cache *cache, u64 bits)
 
 static int noinline find_search_start(struct btrfs_root *root,
                              struct btrfs_block_group_cache **cache_ret,
-                             u64 *start_ret, int num, int data)
+                             u64 *start_ret, u64 num, int data)
 {
        int ret;
        struct btrfs_block_group_cache *cache = *cache_ret;
@@ -188,21 +245,22 @@ static int noinline find_search_start(struct btrfs_root *root,
        u64 search_start = *start_ret;
        int wrapped = 0;
 
-       if (!cache)
-               goto out;
-
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
        free_space_cache = &root->fs_info->free_space_cache;
 
+       if (!cache)
+               goto out;
+
 again:
        ret = cache_block_group(root, cache);
-       if (ret)
+       if (ret) {
                goto out;
+       }
 
        last = max(search_start, cache->key.objectid);
-       if (!block_group_bits(cache, data) || cache->ro) {
+       if (!block_group_bits(cache, data) || cache->ro)
                goto new_group;
-       }
 
        spin_lock_irq(&free_space_cache->lock);
        state = find_first_extent_bit_state(free_space_cache, last, EXTENT_DIRTY);
@@ -217,20 +275,17 @@ again:
                start = max(last, state->start);
                last = state->end + 1;
                if (last - start < num) {
-                       if (last == cache->key.objectid + cache->key.offset)
-                               cache_miss = start;
                        do {
                                state = extent_state_next(state);
                        } while(state && !(state->state & EXTENT_DIRTY));
                        continue;
                }
                spin_unlock_irq(&free_space_cache->lock);
-               if (cache->ro)
+               if (cache->ro) {
                        goto new_group;
+               }
                if (start + num > cache->key.objectid + cache->key.offset)
                        goto new_group;
-               if (start + num  > total_fs_bytes)
-                       goto new_group;
                if (!block_group_bits(cache, data)) {
                        printk("block group bits don't match %Lu %d\n", cache->flags, data);
                }
@@ -248,7 +303,7 @@ out:
 new_group:
        last = cache->key.objectid + cache->key.offset;
 wrapped:
-       cache = btrfs_lookup_block_group(root->fs_info, last);
+       cache = btrfs_lookup_first_block_group(root->fs_info, last);
        if (!cache || cache->key.objectid >= total_fs_bytes) {
 no_cache:
                if (!wrapped) {
@@ -261,13 +316,13 @@ no_cache:
        if (cache_miss && !cache->cached) {
                cache_block_group(root, cache);
                last = cache_miss;
-               cache = btrfs_lookup_block_group(root->fs_info, last);
+               cache = btrfs_lookup_first_block_group(root->fs_info, last);
        }
-       cache = btrfs_find_block_group(root, cache, last, data, 0);
+       cache_miss = 0;
+       cache = __btrfs_find_block_group(root, cache, last, data, 0);
        if (!cache)
                goto no_cache;
        *cache_ret = cache;
-       cache_miss = 0;
        goto again;
 }
 
@@ -292,10 +347,10 @@ 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;
@@ -303,28 +358,26 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
        struct btrfs_fs_info *info = root->fs_info;
        u64 used;
        u64 last = 0;
-       u64 hint_last;
        u64 start;
        u64 end;
        u64 free_check;
        u64 ptr;
-       u64 total_fs_bytes;
        int bit;
        int ret;
        int full_search = 0;
        int factor = 10;
+       int wrapped = 0;
 
        block_group_cache = &info->block_group_cache;
-       total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
 
        if (data & BTRFS_BLOCK_GROUP_METADATA)
                factor = 9;
 
        bit = block_group_state_bits(data);
 
-       if (search_start && search_start < total_fs_bytes) {
+       if (search_start) {
                struct btrfs_block_group_cache *shint;
-               shint = btrfs_lookup_block_group(info, search_start);
+               shint = btrfs_lookup_first_block_group(info, search_start);
                if (shint && block_group_bits(shint, data) && !shint->ro) {
                        used = btrfs_block_group_used(&shint->item);
                        if (used + shint->pinned <
@@ -333,24 +386,18 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
                        }
                }
        }
-       if (hint && !hint->ro && block_group_bits(hint, data) &&
-           hint->key.objectid < total_fs_bytes) {
+       if (hint && !hint->ro && block_group_bits(hint, data)) {
                used = btrfs_block_group_used(&hint->item);
                if (used + hint->pinned <
                    div_factor(hint->key.offset, factor)) {
                        return hint;
                }
                last = hint->key.objectid + hint->key.offset;
-               hint_last = last;
        } else {
                if (hint)
-                       hint_last = max(hint->key.objectid, search_start);
+                       last = max(hint->key.objectid, search_start);
                else
-                       hint_last = search_start;
-
-               if (hint_last >= total_fs_bytes)
-                       hint_last = search_start;
-               last = hint_last;
+                       last = search_start;
        }
 again:
        while(1) {
@@ -360,23 +407,17 @@ again:
                        break;
 
                ret = get_state_private(block_group_cache, start, &ptr);
-               if (ret)
-                       break;
+               if (ret) {
+                       last = end + 1;
+                       continue;
+               }
 
                cache = (struct btrfs_block_group_cache *)(unsigned long)ptr;
                last = cache->key.objectid + cache->key.offset;
                used = btrfs_block_group_used(&cache->item);
 
-               if (cache->key.objectid > total_fs_bytes)
-                       break;
-
                if (!cache->ro && block_group_bits(cache, data)) {
-                       if (full_search)
-                               free_check = cache->key.offset;
-                       else
-                               free_check = div_factor(cache->key.offset,
-                                                       factor);
-
+                       free_check = div_factor(cache->key.offset, factor);
                        if (used + cache->pinned < free_check) {
                                found_group = cache;
                                goto found;
@@ -384,15 +425,33 @@ again:
                }
                cond_resched();
        }
-       if (!full_search) {
+       if (!wrapped) {
+               last = search_start;
+               wrapped = 1;
+               goto again;
+       }
+       if (!full_search && factor < 10) {
                last = search_start;
                full_search = 1;
+               factor = 10;
                goto again;
        }
 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)
 {
@@ -628,7 +687,7 @@ 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,
@@ -678,6 +737,22 @@ 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)
 {
@@ -742,6 +817,10 @@ 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)
@@ -836,33 +915,9 @@ 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)
@@ -879,6 +934,7 @@ 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++) {
@@ -895,7 +951,7 @@ 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);
@@ -906,7 +962,7 @@ 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,
@@ -917,6 +973,7 @@ 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);
@@ -947,6 +1004,7 @@ fail:
                }
        }
 #endif
+       mutex_unlock(&root->fs_info->alloc_mutex);
        return ret;
 }
 
@@ -1001,6 +1059,7 @@ 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);
@@ -1027,6 +1086,7 @@ 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;
 }
 
@@ -1070,6 +1130,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
        found->bytes_used = bytes_used;
        found->bytes_pinned = 0;
        found->full = 0;
+       found->force_alloc = 0;
        *space_info = found;
        return 0;
 }
@@ -1120,7 +1181,7 @@ static u64 reduce_alloc_profile(struct btrfs_root *root, u64 flags)
 
 static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                          struct btrfs_root *extent_root, u64 alloc_bytes,
-                         u64 flags)
+                         u64 flags, int force)
 {
        struct btrfs_space_info *space_info;
        u64 thresh;
@@ -1138,27 +1199,34 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
        }
        BUG_ON(!space_info);
 
+       if (space_info->force_alloc) {
+               force = 1;
+               space_info->force_alloc = 0;
+       }
        if (space_info->full)
-               return 0;
+               goto out;
 
        thresh = div_factor(space_info->total_bytes, 6);
-       if ((space_info->bytes_used + space_info->bytes_pinned + alloc_bytes) <
+       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_unlock;
        }
-
        BUG_ON(ret);
 
        ret = btrfs_make_block_group(trans, extent_root, 0, flags,
                     BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);
        BUG_ON(ret);
-
+out_unlock:
+       mutex_unlock(&extent_root->fs_info->chunk_mutex);
+out:
        return 0;
 }
 
@@ -1175,6 +1243,7 @@ static int update_block_group(struct btrfs_trans_handle *trans,
        u64 start;
        u64 end;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        while(total) {
                cache = btrfs_lookup_block_group(info, bytenr);
                if (!cache) {
@@ -1230,6 +1299,7 @@ static int update_pinned_extents(struct btrfs_root *root,
        struct btrfs_block_group_cache *cache;
        struct btrfs_fs_info *fs_info = root->fs_info;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        if (pin) {
                set_extent_dirty(&fs_info->pinned_extents,
                                bytenr, bytenr + num - 1, GFP_NOFS);
@@ -1295,6 +1365,7 @@ 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);
@@ -1304,6 +1375,7 @@ 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;
 }
 
@@ -1322,6 +1394,7 @@ static int finish_current_insert(struct btrfs_trans_handle *trans,
        int level;
        int err = 0;
 
+       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
        btrfs_set_stack_extent_refs(&extent_item, 1);
        btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
        path = btrfs_alloc_path();
@@ -1338,19 +1411,26 @@ static int finish_current_insert(struct btrfs_trans_handle *trans,
                                        &extent_item, sizeof(extent_item));
                clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
                                  GFP_NOFS);
-               eb = read_tree_block(extent_root, ins.objectid, ins.offset);
+               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;
@@ -1360,12 +1440,14 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
                          int pending)
 {
        int err = 0;
-       struct extent_buffer *buf;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        if (!pending) {
+               struct extent_buffer *buf;
                buf = btrfs_find_tree_block(root, bytenr, num_bytes);
                if (buf) {
-                       if (btrfs_buffer_uptodate(buf)) {
+                       if (!btrfs_try_tree_lock(buf) &&
+                           btrfs_buffer_uptodate(buf, 0)) {
                                u64 transid =
                                    root->fs_info->running_transaction->transid;
                                u64 header_transid =
@@ -1374,9 +1456,11 @@ 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);
                }
@@ -1411,6 +1495,7 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
        struct btrfs_extent_item *ei;
        u32 refs;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        key.objectid = bytenr;
        btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
        key.offset = num_bytes;
@@ -1502,9 +1587,11 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                }
 
                /* block accounting for super block */
+               spin_lock_irq(&info->delalloc_lock);
                super_used = btrfs_super_bytes_used(&info->super_copy);
                btrfs_set_super_bytes_used(&info->super_copy,
                                           super_used - num_bytes);
+               spin_unlock_irq(&info->delalloc_lock);
 
                /* block accounting for root item */
                root_used = btrfs_root_used(&root->root_item);
@@ -1538,6 +1625,7 @@ static int del_pending_extents(struct btrfs_trans_handle *trans, struct
        struct extent_io_tree *pending_del;
        struct extent_io_tree *pinned_extents;
 
+       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
        pending_del = &extent_root->fs_info->pending_del;
        pinned_extents = &extent_root->fs_info->pinned_extents;
 
@@ -1562,10 +1650,11 @@ 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;
@@ -1586,6 +1675,22 @@ 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);
@@ -1618,11 +1723,16 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
        struct btrfs_block_group_cache *block_group;
        int full_scan = 0;
        int wrapped = 0;
+       int chunk_alloc_done = 0;
        int empty_cluster = 2 * 1024 * 1024;
+       int allowed_chunk_alloc = 0;
 
        WARN_ON(num_bytes < root->sectorsize);
        btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);
 
+       if (orig_root->ref_cows || empty_size)
+               allowed_chunk_alloc = 1;
+
        if (data & BTRFS_BLOCK_GROUP_METADATA) {
                last_ptr = &root->fs_info->last_alloc;
                empty_cluster = 256 * 1024;
@@ -1647,15 +1757,15 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                search_end = btrfs_super_total_bytes(&info->super_copy);
 
        if (hint_byte) {
-               block_group = btrfs_lookup_block_group(info, hint_byte);
+               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);
        }
@@ -1665,17 +1775,28 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
 
 check_failed:
        if (!block_group) {
-               block_group = btrfs_lookup_block_group(info, search_start);
+               block_group = btrfs_lookup_first_block_group(info,
+                                                            search_start);
                if (!block_group)
-                       block_group = btrfs_lookup_block_group(info,
+                       block_group = btrfs_lookup_first_block_group(info,
                                                       orig_search_start);
        }
+       if (full_scan && !chunk_alloc_done) {
+               if (allowed_chunk_alloc) {
+                       do_chunk_alloc(trans, root,
+                                    num_bytes + 2 * 1024 * 1024, data, 1);
+                       allowed_chunk_alloc = 0;
+               } else if (block_group && block_group_bits(block_group, data)) {
+                       block_group->space_info->force_alloc = 1;
+               }
+               chunk_alloc_done = 1;
+       }
        ret = find_search_start(root, &block_group, &search_start,
                                total_needed, data);
        if (ret == -ENOSPC && last_ptr && *last_ptr) {
                *last_ptr = 0;
-               block_group = btrfs_lookup_block_group(info,
-                                                      orig_search_start);
+               block_group = btrfs_lookup_first_block_group(info,
+                                                            orig_search_start);
                search_start = orig_search_start;
                ret = find_search_start(root, &block_group, &search_start,
                                        total_needed, data);
@@ -1691,7 +1812,7 @@ check_failed:
                        empty_size += empty_cluster;
                        total_needed += empty_size;
                }
-               block_group = btrfs_lookup_block_group(info,
+               block_group = btrfs_lookup_first_block_group(info,
                                                       orig_search_start);
                search_start = orig_search_start;
                ret = find_search_start(root, &block_group,
@@ -1764,9 +1885,9 @@ enospc:
                } else
                        wrapped = 1;
        }
-       block_group = btrfs_lookup_block_group(info, search_start);
+       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;
 
@@ -1803,6 +1924,8 @@ 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;
@@ -1818,17 +1941,21 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
        }
 again:
        data = reduce_alloc_profile(root, data);
-       if (root->ref_cows) {
+       /*
+        * the only place that sets empty_size is btrfs_realloc_node, which
+        * is not called recursively on allocations
+        */
+       if (empty_size || root->ref_cows) {
                if (!(data & BTRFS_BLOCK_GROUP_METADATA)) {
                        ret = do_chunk_alloc(trans, root->fs_info->extent_root,
-                                            2 * 1024 * 1024,
-                                            BTRFS_BLOCK_GROUP_METADATA |
-                                            (info->metadata_alloc_profile &
-                                             info->avail_metadata_alloc_bits));
+                                    2 * 1024 * 1024,
+                                    BTRFS_BLOCK_GROUP_METADATA |
+                                    (info->metadata_alloc_profile &
+                                     info->avail_metadata_alloc_bits), 0);
                        BUG_ON(ret);
                }
                ret = do_chunk_alloc(trans, root->fs_info->extent_root,
-                                    num_bytes + 2 * 1024 * 1024, data);
+                                    num_bytes + 2 * 1024 * 1024, data, 0);
                BUG_ON(ret);
        }
 
@@ -1841,18 +1968,23 @@ again:
        if (ret == -ENOSPC && num_bytes > min_alloc_size) {
                num_bytes = num_bytes >> 1;
                num_bytes = max(num_bytes, min_alloc_size);
+               do_chunk_alloc(trans, root->fs_info->extent_root,
+                              num_bytes, data, 1);
                goto 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 */
+       spin_lock_irq(&info->delalloc_lock);
        super_used = btrfs_super_bytes_used(&info->super_copy);
        btrfs_set_super_bytes_used(&info->super_copy, super_used + num_bytes);
+       spin_unlock_irq(&info->delalloc_lock);
 
        /* block accounting for root item */
        root_used = btrfs_root_used(&root->root_item);
@@ -1907,11 +2039,11 @@ 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:
@@ -1921,36 +2053,15 @@ 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.
  */
 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,
@@ -1980,6 +2091,7 @@ 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);
 
@@ -1990,8 +2102,6 @@ struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 
        set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
                         buf->start + buf->len - 1, GFP_NOFS);
-       if (!btrfs_test_opt(root, SSD))
-               btrfs_set_buffer_defrag(buf);
        trans->blocks_used++;
        return buf;
 }
@@ -2030,7 +2140,7 @@ 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);
@@ -2075,16 +2185,30 @@ static void noinline reada_walk_down(struct btrfs_root *root,
                                continue;
                        }
                }
-               mutex_unlock(&root->fs_info->fs_mutex);
-               ret = readahead_tree_block(root, bytenr, blocksize);
+               ret = readahead_tree_block(root, bytenr, blocksize,
+                                          btrfs_node_ptr_generation(node, i));
                last = bytenr + blocksize;
                cond_resched();
-               mutex_lock(&root->fs_info->fs_mutex);
                if (ret)
                        break;
        }
 }
 
+/*
+ * we want to avoid as much random IO as we can with the alloc mutex
+ * held, so drop the lock and do the lookup, then do it again with the
+ * lock held.
+ */
+int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
+                             u32 *refs)
+{
+       mutex_unlock(&root->fs_info->alloc_mutex);
+       lookup_extent_ref(NULL, root, start, len, refs);
+       cond_resched();
+       mutex_lock(&root->fs_info->alloc_mutex);
+       return lookup_extent_ref(NULL, root, start, len, refs);
+}
+
 /*
  * helper function for drop_snapshot, this walks down the tree dropping ref
  * counts as it goes.
@@ -2096,6 +2220,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
        u64 root_owner;
        u64 root_gen;
        u64 bytenr;
+       u64 ptr_gen;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        struct extent_buffer *parent;
@@ -2103,10 +2228,11 @@ 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,
-                               path->nodes[*level]->start,
+       ret = drop_snap_lookup_refcount(root, path->nodes[*level]->start,
                                path->nodes[*level]->len, &refs);
        BUG_ON(ret);
        if (refs > 1)
@@ -2132,31 +2258,37 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
                        break;
                }
                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);
+
+               ret = drop_snap_lookup_refcount(root, bytenr, blocksize, &refs);
                BUG_ON(ret);
                if (refs != 1) {
                        parent = path->nodes[*level];
                        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);
                        continue;
                }
                next = btrfs_find_tree_block(root, bytenr, blocksize);
-               if (!next || !btrfs_buffer_uptodate(next)) {
+               if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
                        free_extent_buffer(next);
-                       reada_walk_down(root, cur, path->slots[*level]);
+                       mutex_unlock(&root->fs_info->alloc_mutex);
 
-                       mutex_unlock(&root->fs_info->fs_mutex);
-                       next = read_tree_block(root, bytenr, blocksize);
-                       mutex_lock(&root->fs_info->fs_mutex);
+                       if (path->slots[*level] == 0)
+                               reada_walk_down(root, cur, path->slots[*level]);
+
+                       next = read_tree_block(root, bytenr, blocksize,
+                                              ptr_gen);
+                       cond_resched();
+                       mutex_lock(&root->fs_info->alloc_mutex);
 
                        /* we've dropped the lock, double check */
-                       ret = lookup_extent_ref(trans, root, bytenr,
+                       ret = drop_snap_lookup_refcount(root, bytenr,
                                                blocksize, &refs);
                        BUG_ON(ret);
                        if (refs != 1) {
@@ -2166,15 +2298,13 @@ 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);
                                BUG_ON(ret);
                                continue;
                        }
-               } else if (next) {
-                       btrfs_verify_block_csum(root, next);
                }
                WARN_ON(*level <= 0);
                if (path->nodes[*level-1])
@@ -2196,13 +2326,15 @@ 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);
+       cond_resched();
        return 0;
 }
 
@@ -2276,6 +2408,7 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
        int orig_level;
        struct btrfs_root_item *root_item = &root->root_item;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->drop_mutex));
        path = btrfs_alloc_path();
        BUG_ON(!path);
 
@@ -2302,6 +2435,16 @@ 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)));
+               /*
+                * unlock our path, this is safe because only this
+                * function is allowed to delete this snapshot
+                */
+               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);
@@ -2315,8 +2458,10 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                        break;
                if (wret < 0)
                        ret = wret;
-               ret = -EAGAIN;
-               break;
+               if (trans->transaction->in_commit) {
+                       ret = -EAGAIN;
+                       break;
+               }
        }
        for (i = 0; i <= orig_level; i++) {
                if (path->nodes[i]) {
@@ -2335,6 +2480,8 @@ 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);
@@ -2354,6 +2501,7 @@ 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;
 }
 
@@ -2474,7 +2622,6 @@ static int find_root_for_ref(struct btrfs_root *root,
        u64 root_search_start = BTRFS_FS_TREE_OBJECTID;
        u64 found_bytenr;
        int ret;
-       int i;
 
        root_location.offset = (u64)-1;
        root_location.type = BTRFS_ROOT_ITEM_KEY;
@@ -2498,12 +2645,6 @@ static int find_root_for_ref(struct btrfs_root *root,
                                found_bytenr = path->nodes[level]->start;
                }
 
-               for (i = level; i < BTRFS_MAX_LEVEL; i++) {
-                       if (!path->nodes[i])
-                               break;
-                       free_extent_buffer(path->nodes[i]);
-                       path->nodes[i] = NULL;
-               }
                btrfs_release_path(cur_root, path);
 
                if (found_bytenr == bytenr) {
@@ -2534,7 +2675,11 @@ out:
  */
 static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                                  struct btrfs_path *path,
-                                 struct btrfs_key *extent_key)
+                                 struct btrfs_key *extent_key,
+                                 u64 *last_file_objectid,
+                                 u64 *last_file_offset,
+                                 u64 *last_file_root,
+                                 u64 last_extent)
 {
        struct inode *inode;
        struct btrfs_root *found_root;
@@ -2548,6 +2693,8 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
        int ret;
        int level;
 
+       WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
+
        ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                             struct btrfs_extent_ref);
        ref_root = btrfs_ref_root(path->nodes[0], ref);
@@ -2566,6 +2713,7 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
        found_root = btrfs_read_fs_root_no_name(extent_root->fs_info,
                                                &root_location);
        BUG_ON(!found_root);
+       mutex_unlock(&extent_root->fs_info->alloc_mutex);
 
        if (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
                found_key.objectid = ref_objectid;
@@ -2573,6 +2721,12 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                found_key.offset = ref_offset;
                level = 0;
 
+               if (last_extent == extent_key->objectid &&
+                   *last_file_objectid == ref_objectid &&
+                   *last_file_offset == ref_offset &&
+                   *last_file_root == ref_root)
+                       goto out;
+
                ret = find_root_for_ref(extent_root, path, &found_key,
                                        level, 1, &found_root,
                                        extent_key->objectid);
@@ -2580,7 +2734,12 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                if (ret)
                        goto out;
 
-               mutex_unlock(&extent_root->fs_info->fs_mutex);
+               if (last_extent == extent_key->objectid &&
+                   *last_file_objectid == ref_objectid &&
+                   *last_file_offset == ref_offset &&
+                   *last_file_root == ref_root)
+                       goto out;
+
                inode = btrfs_iget_locked(extent_root->fs_info->sb,
                                          ref_objectid, found_root);
                if (inode->i_state & I_NEW) {
@@ -2596,20 +2755,23 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                /* this can happen if the reference is not against
                 * the latest version of the tree root
                 */
-               if (is_bad_inode(inode)) {
-                       mutex_lock(&extent_root->fs_info->fs_mutex);
+               if (is_bad_inode(inode))
                        goto out;
-               }
+
+               *last_file_objectid = inode->i_ino;
+               *last_file_root = found_root->root_key.objectid;
+               *last_file_offset = ref_offset;
+
                relocate_inode_pages(inode, ref_offset, extent_key->offset);
                iput(inode);
-               mutex_lock(&extent_root->fs_info->fs_mutex);
        } else {
                struct btrfs_trans_handle *trans;
                struct extent_buffer *eb;
-               int i;
+               int needs_lock = 0;
 
                eb = read_tree_block(found_root, extent_key->objectid,
-                                    extent_key->offset);
+                                    extent_key->offset, 0);
+               btrfs_tree_lock(eb);
                level = btrfs_header_level(eb);
 
                if (level == 0)
@@ -2617,6 +2779,7 @@ 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,
@@ -2626,24 +2789,40 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                if (ret)
                        goto out;
 
+               /*
+                * right here almost anything could happen to our key,
+                * but that's ok.  The cow below will either relocate it
+                * or someone else will have relocated it.  Either way,
+                * it is in a different spot than it was before and
+                * we're happy.
+                */
+
                trans = btrfs_start_transaction(found_root, 1);
 
+               if (found_root == extent_root->fs_info->extent_root ||
+                   found_root == extent_root->fs_info->chunk_root ||
+                   found_root == extent_root->fs_info->dev_root) {
+                       needs_lock = 1;
+                       mutex_lock(&extent_root->fs_info->alloc_mutex);
+               }
+
                path->lowest_level = level;
                path->reada = 2;
                ret = btrfs_search_slot(trans, found_root, &found_key, path,
                                        0, 1);
                path->lowest_level = 0;
-               for (i = level; i < BTRFS_MAX_LEVEL; i++) {
-                       if (!path->nodes[i])
-                               break;
-                       free_extent_buffer(path->nodes[i]);
-                       path->nodes[i] = NULL;
-               }
                btrfs_release_path(found_root, path);
+
+               if (found_root == found_root->fs_info->extent_root)
+                       btrfs_extent_post_op(trans, found_root);
+               if (needs_lock)
+                       mutex_unlock(&extent_root->fs_info->alloc_mutex);
+
                btrfs_end_transaction(trans, found_root);
-       }
 
+       }
 out:
+       mutex_lock(&extent_root->fs_info->alloc_mutex);
        return 0;
 }
 
@@ -2675,6 +2854,10 @@ static int noinline relocate_one_extent(struct btrfs_root *extent_root,
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
+       u64 last_file_objectid = 0;
+       u64 last_file_root = 0;
+       u64 last_file_offset = (u64)-1;
+       u64 last_extent = 0;
        u32 nritems;
        u32 item_size;
        int ret = 0;
@@ -2719,9 +2902,13 @@ static int noinline relocate_one_extent(struct btrfs_root *extent_root,
                key.offset = found_key.offset + 1;
                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 
-               ret = relocate_one_reference(extent_root, path, extent_key);
+               ret = relocate_one_reference(extent_root, path, extent_key,
+                                            &last_file_objectid,
+                                            &last_file_offset,
+                                            &last_file_root, last_extent);
                if (ret)
                        goto out;
+               last_extent = extent_key->objectid;
        }
        ret = 0;
 out:
@@ -2767,6 +2954,38 @@ static u64 update_block_group_flags(struct btrfs_root *root, u64 flags)
        return flags;
 }
 
+int __alloc_chunk_for_shrink(struct btrfs_root *root,
+                    struct btrfs_block_group_cache *shrink_block_group,
+                    int force)
+{
+       struct btrfs_trans_handle *trans;
+       u64 new_alloc_flags;
+       u64 calc;
+
+       if (btrfs_block_group_used(&shrink_block_group->item) > 0) {
+
+               mutex_unlock(&root->fs_info->alloc_mutex);
+               trans = btrfs_start_transaction(root, 1);
+               mutex_lock(&root->fs_info->alloc_mutex);
+
+               new_alloc_flags = update_block_group_flags(root,
+                                                  shrink_block_group->flags);
+               if (new_alloc_flags != shrink_block_group->flags) {
+                       calc =
+                            btrfs_block_group_used(&shrink_block_group->item);
+               } else {
+                       calc = shrink_block_group->key.offset;
+               }
+               do_chunk_alloc(trans, root->fs_info->extent_root,
+                              calc + 2 * 1024 * 1024, new_alloc_flags, force);
+
+               mutex_unlock(&root->fs_info->alloc_mutex);
+               btrfs_end_transaction(trans, root);
+               mutex_lock(&root->fs_info->alloc_mutex);
+       }
+       return 0;
+}
+
 int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
 {
        struct btrfs_trans_handle *trans;
@@ -2775,7 +2994,6 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
        u64 cur_byte;
        u64 total_found;
        u64 shrink_last_byte;
-       u64 new_alloc_flags;
        struct btrfs_block_group_cache *shrink_block_group;
        struct btrfs_fs_info *info = root->fs_info;
        struct btrfs_key key;
@@ -2785,11 +3003,13 @@ 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);
 
-       shrink_last_byte = shrink_start + shrink_block_group->key.offset;
+       shrink_last_byte = shrink_block_group->key.objectid +
+               shrink_block_group->key.offset;
 
        shrink_block_group->space_info->total_bytes -=
                shrink_block_group->key.offset;
@@ -2801,23 +3021,10 @@ int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
               (unsigned long long)shrink_start,
               (unsigned long long)shrink_block_group->flags);
 
+       __alloc_chunk_for_shrink(root, shrink_block_group, 1);
+
 again:
-       if (btrfs_block_group_used(&shrink_block_group->item) > 0) {
-               u64 calc;
 
-               trans = btrfs_start_transaction(root, 1);
-               new_alloc_flags = update_block_group_flags(root,
-                                                  shrink_block_group->flags);
-               if (new_alloc_flags != shrink_block_group->flags) {
-                       calc =
-                            btrfs_block_group_used(&shrink_block_group->item);
-               } else {
-                       calc = shrink_block_group->key.offset;
-               }
-               do_chunk_alloc(trans, root->fs_info->extent_root,
-                              calc + 2 * 1024 * 1024, new_alloc_flags);
-               btrfs_end_transaction(trans, root);
-       }
        shrink_block_group->ro = 1;
 
        total_found = 0;
@@ -2851,9 +3058,9 @@ again:
                if (ret < 0)
                        goto out;
 
+next:
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
-next:
                if (path->slots[0] >= nritems) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
@@ -2873,9 +3080,7 @@ next:
 
                if (progress && need_resched()) {
                        memcpy(&key, &found_key, sizeof(key));
-                       mutex_unlock(&root->fs_info->fs_mutex);
                        cond_resched();
-                       mutex_lock(&root->fs_info->fs_mutex);
                        btrfs_release_path(root, path);
                        btrfs_search_slot(NULL, root, &key, path, 0, 0);
                        progress = 0;
@@ -2885,6 +3090,8 @@ next:
 
                if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
                    found_key.objectid + found_key.offset <= cur_byte) {
+                       memcpy(&key, &found_key, sizeof(key));
+                       key.offset++;
                        path->slots[0]++;
                        goto next;
                }
@@ -2894,6 +3101,7 @@ next:
                key.objectid = cur_byte;
                btrfs_release_path(root, path);
                ret = relocate_one_extent(root, path, &found_key);
+               __alloc_chunk_for_shrink(root, shrink_block_group, 0);
        }
 
        btrfs_release_path(root, path);
@@ -2902,15 +3110,15 @@ next:
                printk("btrfs relocate found %llu last extent was %llu\n",
                       (unsigned long long)total_found,
                       (unsigned long long)found_key.objectid);
+               mutex_unlock(&root->fs_info->alloc_mutex);
                trans = btrfs_start_transaction(tree_root, 1);
                btrfs_commit_transaction(trans, tree_root);
 
-               mutex_unlock(&root->fs_info->fs_mutex);
                btrfs_clean_old_snapshots(tree_root);
-               mutex_lock(&root->fs_info->fs_mutex);
 
                trans = btrfs_start_transaction(tree_root, 1);
                btrfs_commit_transaction(trans, tree_root);
+               mutex_lock(&root->fs_info->alloc_mutex);
                goto again;
        }
 
@@ -2918,7 +3126,10 @@ next:
         * we've freed all the extents, now remove the block
         * group item from the tree
         */
+       mutex_unlock(&root->fs_info->alloc_mutex);
+
        trans = btrfs_start_transaction(root, 1);
+       mutex_lock(&root->fs_info->alloc_mutex);
        memcpy(&key, &shrink_block_group->key, sizeof(key));
 
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
@@ -2927,36 +3138,49 @@ next:
        if (ret < 0)
                goto out;
 
-       leaf = path->nodes[0];
-       nritems = btrfs_header_nritems(leaf);
-       btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-       kfree(shrink_block_group);
-
-       clear_extent_bits(&info->block_group_cache, found_key.objectid,
-                         found_key.objectid + found_key.offset - 1,
+       clear_extent_bits(&info->block_group_cache, key.objectid,
+                         key.objectid + key.offset - 1,
                          (unsigned int)-1, GFP_NOFS);
 
+
+       clear_extent_bits(&info->free_space_cache,
+                          key.objectid, key.objectid + key.offset - 1,
+                          (unsigned int)-1, GFP_NOFS);
+
+       memset(shrink_block_group, 0, sizeof(*shrink_block_group));
+       kfree(shrink_block_group);
+
        btrfs_del_item(trans, root, path);
-       clear_extent_dirty(&info->free_space_cache,
-                          shrink_start, shrink_last_byte - 1,
-                          GFP_NOFS);
+       btrfs_release_path(root, path);
+       mutex_unlock(&root->fs_info->alloc_mutex);
        btrfs_commit_transaction(trans, root);
+
+       mutex_lock(&root->fs_info->alloc_mutex);
+
+       /* the code to unpin extents might set a few bits in the free
+        * space cache for this range again
+        */
+       clear_extent_bits(&info->free_space_cache,
+                          key.objectid, key.objectid + key.offset - 1,
+                          (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];
@@ -2965,18 +3189,20 @@ 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;
 }
 
@@ -3002,6 +3228,7 @@ 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) {
@@ -3057,6 +3284,7 @@ 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;
 }
 
@@ -3071,6 +3299,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
        struct btrfs_block_group_cache *cache;
        struct extent_io_tree *block_group_cache;
 
+       WARN_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
        extent_root = root->fs_info->extent_root;
        block_group_cache = &root->fs_info->block_group_cache;
 
@@ -3078,9 +3307,8 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
        BUG_ON(!cache);
        cache->key.objectid = chunk_offset;
        cache->key.offset = size;
-
        btrfs_set_key_type(&cache->key, BTRFS_BLOCK_GROUP_ITEM_KEY);
-       memset(&cache->item, 0, sizeof(cache->item));
+
        btrfs_set_block_group_used(&cache->item, bytes_used);
        btrfs_set_block_group_chunk_objectid(&cache->item, chunk_objectid);
        cache->flags = type;
@@ -3105,5 +3333,6 @@ 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;
 }
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