fs: convert fs shrinkers to new scan/count API

Convert the filesystem shrinkers to use the new API, and standardise some
of the behaviours of the shrinkers at the same time.  For example,
nr_to_scan means the number of objects to scan, not the number of objects
to free.

I refactored the CIFS idmap shrinker a little - it really needs to be
broken up into a shrinker per tree and keep an item count with the tree
root so that we don't need to walk the tree every time the shrinker needs
to count the number of objects in the tree (i.e.  all the time under
memory pressure).

[glommer@openvz.org: fixes for ext4, ubifs, nfs, cifs and glock. Fixes are needed mainly due to new code merged in the tree]
[assorted fixes folded in]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 18 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 13eee847605c..831d49a4111f 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -687,44 +687,37 @@ int dquot_quota_sync(struct super_block *sb, int type)
 }
 EXPORT_SYMBOL(dquot_quota_sync);
 
-/* Free unused dquots from cache */
-static void prune_dqcache(int count)
+static unsigned long
+dqcache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	struct list_head *head;
 	struct dquot *dquot;
+	unsigned long freed = 0;
 
 	head = free_dquots.prev;
-	while (head != &free_dquots && count) {
+	while (head != &free_dquots && sc->nr_to_scan) {
 		dquot = list_entry(head, struct dquot, dq_free);
 		remove_dquot_hash(dquot);
 		remove_free_dquot(dquot);
 		remove_inuse(dquot);
 		do_destroy_dquot(dquot);
-		count--;
+		sc->nr_to_scan--;
+		freed++;
 		head = free_dquots.prev;
 	}
+	return freed;
 }
 
-/*
- * This is called from kswapd when we think we need some
- * more memory
- */
-static int shrink_dqcache_memory(struct shrinker *shrink,
-				 struct shrink_control *sc)
+static unsigned long
+dqcache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 {
-	int nr = sc->nr_to_scan;
-
-	if (nr) {
-		spin_lock(&dq_list_lock);
-		prune_dqcache(nr);
-		spin_unlock(&dq_list_lock);
-	}
 	return vfs_pressure_ratio(
 	percpu_counter_read_positive(&dqstats.counter[DQST_FREE_DQUOTS]));
 }
 
 static struct shrinker dqcache_shrinker = {
-	.shrink = shrink_dqcache_memory,
+	.count_objects = dqcache_shrink_count,
+	.scan_objects = dqcache_shrink_scan,
 	.seeks = DEFAULT_SEEKS,
 };