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

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

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 239e9d8..8f44178 100644 (file)
--- 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;
                }