Btrfs: fix to search previous metadata extent item since skinny metadata

There is a bug that using btrfs_previous_item() to search metadata extent item.
This is because in btrfs_previous_item(), we need type match, however, since
skinny metada was introduced by josef, we may mix this two types. So just
use btrfs_previous_item() is not working right.

To keep btrfs_previous_item() like normal tree search, i introduce another
function btrfs_previous_extent_item().

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 9e9de68eb813..30f5b11d7dd3 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -5955,3 +5955,46 @@ int btrfs_previous_item(struct btrfs_root *root,
         }
         return 1;
 }
+
+/*
+ * search in extent tree to find a previous Metadata/Data extent item with
+ * min objecitd.
+ *
+ * returns 0 if something is found, 1 if nothing was found and < 0 on error
+ */
+int btrfs_previous_extent_item(struct btrfs_root *root,
+                        struct btrfs_path *path, u64 min_objectid)
+{
+        struct btrfs_key found_key;
+        struct extent_buffer *leaf;
+        u32 nritems;
+        int ret;
+
+        while (1) {
+                if (path->slots[0] == 0) {
+                        btrfs_set_path_blocking(path);
+                        ret = btrfs_prev_leaf(root, path);
+                        if (ret != 0)
+                                return ret;
+                } else {
+                        path->slots[0]--;
+                }
+                leaf = path->nodes[0];
+                nritems = btrfs_header_nritems(leaf);
+                if (nritems == 0)
+                        return 1;
+                if (path->slots[0] == nritems)
+                        path->slots[0]--;
+
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                if (found_key.objectid < min_objectid)
+                        break;
+                if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
+                    found_key.type == BTRFS_METADATA_ITEM_KEY)
+                        return 0;
+                if (found_key.objectid == min_objectid &&
+                    found_key.type < BTRFS_EXTENT_ITEM_KEY)
+                        break;
+        }
+        return 1;
+}