Btrfs: comment for loop in tree_mod_log_insert_move

Emphasis the way tree_mod_log_insert_move avoids adding
MOD_LOG_KEY_REMOVE_WHILE_MOVING operations, depending on the direction of
the move operation.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index f6739903d072..eba44b076829 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -596,6 +596,11 @@ tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
         if (tree_mod_dont_log(fs_info, eb))
                 return 0;
 
+        /*
+         * When we override something during the move, we log these removals.
+         * This can only happen when we move towards the beginning of the
+         * buffer, i.e. dst_slot < src_slot.
+         */
         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
                 ret = tree_mod_log_insert_key_locked(fs_info, eb, i + dst_slot,
                                               MOD_LOG_KEY_REMOVE_WHILE_MOVING);