superblock: add filesystem shrinker operations

Now we have a per-superblock shrinker implementation, we can add a
filesystem specific callout to it to allow filesystem internal
caches to be shrunk by the superblock shrinker.

Rather than perpetuate the multipurpose shrinker callback API (i.e.
nr_to_scan == 0 meaning "tell me how many objects freeable in the
cache), two operations will be added. The first will return the
number of objects that are freeable, the second is the actual
shrinker call.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index d7f35e90b84a..1393742bba9b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1655,6 +1655,8 @@ struct super_operations {
         ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
 #endif
         int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
+        int (*nr_cached_objects)(struct super_block *);
+        void (*free_cached_objects)(struct super_block *, int);
 };
 
 /*