Btrfs: Remove extent back refs in batches, and avoid duplicate searches

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 54 insertions, 9 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 239e9d8669cb..8f441783a6ed 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1251,6 +1251,9 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
         struct btrfs_root *extent_root = info->extent_root;
         struct extent_buffer *leaf;
         int ret;
+        int extent_slot = 0;
+        int found_extent = 0;
+        int num_to_del = 1;
         struct btrfs_extent_item *ei;
         u32 refs;
 
@@ -1267,7 +1270,24 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                                     ref_generation,
                                     owner_objectid, owner_offset, 1);
         if (ret == 0) {
-                ret = btrfs_del_item(trans, extent_root, path);
+                struct btrfs_key found_key;
+                extent_slot = path->slots[0];
+                while(extent_slot > 0) {
+                        extent_slot--;
+                        btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+                                              extent_slot);
+                        if (found_key.objectid != bytenr)
+                                break;
+                        if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
+                            found_key.offset == num_bytes) {
+                                found_extent = 1;
+                                break;
+                        }
+                        if (path->slots[0] - extent_slot > 5)
+                                break;
+                }
+                if (!found_extent)
+                        ret = btrfs_del_item(trans, extent_root, path);
         } else {
                 btrfs_print_leaf(extent_root, path->nodes[0]);
                 WARN_ON(1);
@@ -1276,21 +1296,46 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                        root_objectid, ref_generation, owner_objectid,
                        owner_offset);
         }
-        btrfs_release_path(extent_root, path);
-        ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
-        if (ret < 0)
-                return ret;
-        BUG_ON(ret);
+        if (!found_extent) {
+                btrfs_release_path(extent_root, path);
+                ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
+                if (ret < 0)
+                        return ret;
+                BUG_ON(ret);
+                extent_slot = path->slots[0];
+        }
 
         leaf = path->nodes[0];
-        ei = btrfs_item_ptr(leaf, path->slots[0],
+        ei = btrfs_item_ptr(leaf, extent_slot,
                             struct btrfs_extent_item);
         refs = btrfs_extent_refs(leaf, ei);
         BUG_ON(refs == 0);
         refs -= 1;
         btrfs_set_extent_refs(leaf, ei, refs);
+
         btrfs_mark_buffer_dirty(leaf);
 
+        if (refs == 0 && found_extent && path->slots[0] == extent_slot + 1) {
+                /* if the back ref and the extent are next to each other
+                 * they get deleted below in one shot
+                 */
+                path->slots[0] = extent_slot;
+                num_to_del = 2;
+        } else if (found_extent) {
+                /* otherwise delete the extent back ref */
+                ret = btrfs_del_item(trans, extent_root, path);
+                BUG_ON(ret);
+                /* if refs are 0, we need to setup the path for deletion */
+                if (refs == 0) {
+                        btrfs_release_path(extent_root, path);
+                        ret = btrfs_search_slot(trans, extent_root, &key, path,
+                                                -1, 1);
+                        if (ret < 0)
+                                return ret;
+                        BUG_ON(ret);
+                }
+        }
+
         if (refs == 0) {
                 u64 super_used;
                 u64 root_used;
@@ -1311,8 +1356,8 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                 root_used = btrfs_root_used(&root->root_item);
                 btrfs_set_root_used(&root->root_item,
                                            root_used - num_bytes);
-
-                ret = btrfs_del_item(trans, extent_root, path);
+                ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
+                                      num_to_del);
                 if (ret) {
                         return ret;
                 }