ovl: use plain list filler in indexdir and workdir cleanup
Those two cleanup routines are using the helper ovl_dir_read() with the
merge dir filler, which populates an rb tree, that is never used.
The index dir entry names all have a long (42 bytes) constant prefix, so it
is not surprising that perf top has demostrated high CPU usage by rb tree
population during cleanup of a large index dir:
- 9.53% ovl_fill_merge
- 78.41% ovl_cache_entry_find_link.constprop.27
+ 72.11% strncmp
Use the plain list filler that does not populate the unneeded rb tree.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>