mm: shrink parent dentries when shrinking slab

Teach the dentry slab shrinker to aggressively shrink parent dentries when
shrinking the dentry cache.

This is done to attempt to improve the situation where the dentry slab cache
gets a lot of internal fragmentation due to pages containing directory
dentries.  It is expected that this change will cause some of those dentries
to be reaped earlier, and with less scanning.

Needs careful testing.

Cc: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/dcache.c b/fs/dcache.c
index 681cab81b454ae82f61d2e56074eb0e18d910612..268da2e2bc09f8f4694dafb5a55675dd22b3c8ee 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -879,7 +879,7 @@ static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
        if (nr) {
                if (!(gfp_mask & __GFP_FS))
                        return -1;
-               prune_dcache(nr, NULL, 0);
+               prune_dcache(nr, NULL, 1);
        }
        return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
 }