On Sat 26-11-16 22:17:57, Eric Biggers wrote:
> mbcache entries have an 'e_referenced' bit which users can set with
> mb_cache_entry_touch() to indicate that an entry should be given another
> pass through the LRU list before the shrinker can delete it. However,
> mb_cache_shrink() actually would, when seeing an e_referenced entry at
> the front of the list (the least-recently used end), place it right at
> the front of the list again. The next iteration would then remove the
> entry from the list and delete it. Consequently, e_referenced had
> essentially no effect, so ext2/ext4 xattr blocks would sometimes not be
> reused as often as expected.
>
> Fix this by making the shrinker move e_referenced entries to the back of
> the list rather than the front.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Bah, good spotting. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
BTW, how did you find out?
Honza
> ---
> fs/mbcache.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/mbcache.c b/fs/mbcache.c
> index c5bd19f..31e54c2 100644
> --- a/fs/mbcache.c
> +++ b/fs/mbcache.c
> @@ -286,7 +286,7 @@ static unsigned long mb_cache_shrink(struct mb_cache *cache,
> struct mb_cache_entry, e_list);
> if (entry->e_referenced) {
> entry->e_referenced = 0;
> - list_move_tail(&cache->c_list, &entry->e_list);
> + list_move_tail(&entry->e_list, &cache->c_list);
> continue;
> }
> list_del_init(&entry->e_list);
> --
> 2.8.0.rc3.226.g39d4020
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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