Btrfs: fix btrfs_prev_leaf() previous key computation

If we decrement the key type, we must reset its offset to the largest
possible offset (u64)-1. If we decrement the key's objectid, then we
must reset the key's type and offset to their largest possible values,
(u8)-1 and (u64)-1 respectively. Not doing so can make us miss an
items in the tree.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 8f3d6f893585..a749121203df 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -4827,14 +4827,18 @@ static int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
 
         btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
 
-        if (key.offset > 0)
+        if (key.offset > 0) {
                 key.offset--;
-        else if (key.type > 0)
+        } else if (key.type > 0) {
                 key.type--;
-        else if (key.objectid > 0)
+                key.offset = (u64)-1;
+        } else if (key.objectid > 0) {
                 key.objectid--;
-        else
+                key.type = (u8)-1;
+                key.offset = (u64)-1;
+        } else {
                 return 1;
+        }
 
         btrfs_release_path(path);
         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);