Btrfs: fix a bug of snapshot-aware defrag to make it work on partial extents

[linux-imx.git] / fs / btrfs / inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0fd7647c893249f24580b934e891b601a40b193e..c72033ee6017b09325a752c0e3bb760aa6ffc147 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2166,16 +2166,23 @@ static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
                if (btrfs_file_extent_disk_bytenr(leaf, extent) != old->bytenr)
                        continue;
 
-               extent_offset = btrfs_file_extent_offset(leaf, extent);
-               if (key.offset - extent_offset != offset)
+               /*
+                * 'offset' refers to the exact key.offset,
+                * NOT the 'offset' field in btrfs_extent_data_ref, ie.
+                * (key.offset - extent_offset).
+                */
+               if (key.offset != offset)
                        continue;
 
+               extent_offset = btrfs_file_extent_offset(leaf, extent);
                num_bytes = btrfs_file_extent_num_bytes(leaf, extent);
+
                if (extent_offset >= old->extent_offset + old->offset +
                    old->len || extent_offset + num_bytes <=
                    old->extent_offset + old->offset)
                        continue;
 
+               ret = 0;
                break;
        }
 
@@ -2187,7 +2194,7 @@ static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
 
        backref->root_id = root_id;
        backref->inum = inum;
-       backref->file_pos = offset + extent_offset;
+       backref->file_pos = offset;
        backref->num_bytes = num_bytes;
        backref->extent_offset = extent_offset;
        backref->generation = btrfs_file_extent_generation(leaf, extent);
@@ -2210,7 +2217,8 @@ static noinline bool record_extent_backrefs(struct btrfs_path *path,
        new->path = path;
 
        list_for_each_entry_safe(old, tmp, &new->head, list) {
-               ret = iterate_inodes_from_logical(old->bytenr, fs_info,
+               ret = iterate_inodes_from_logical(old->bytenr +
+                                                 old->extent_offset, fs_info,
                                                  path, record_one_backref,
                                                  old);
                BUG_ON(ret < 0 && ret != -ENOENT);