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>

3 files changed, 24 insertions, 13 deletions

diff --git a/fs/ubifs/shrinker.c b/fs/ubifs/shrinker.c
index 9e1d05666fed..f35135e28e96 100644
--- a/fs/ubifs/shrinker.c
+++ b/fs/ubifs/shrinker.c
@@ -277,18 +277,25 @@ static int kick_a_thread(void)
         return 0;
 }
 
-int ubifs_shrinker(struct shrinker *shrink, struct shrink_control *sc)
+unsigned long ubifs_shrink_count(struct shrinker *shrink,
+                                 struct shrink_control *sc)
 {
-        int nr = sc->nr_to_scan;
-        int freed, contention = 0;
         long clean_zn_cnt = atomic_long_read(&ubifs_clean_zn_cnt);
 
-        if (nr == 0)
-                /*
-                 * Due to the way UBIFS updates the clean znode counter it may
-                 * temporarily be negative.
-                 */
-                return clean_zn_cnt >= 0 ? clean_zn_cnt : 1;
+        /*
+         * Due to the way UBIFS updates the clean znode counter it may
+         * temporarily be negative.
+         */
+        return clean_zn_cnt >= 0 ? clean_zn_cnt : 1;
+}
+
+unsigned long ubifs_shrink_scan(struct shrinker *shrink,
+                                struct shrink_control *sc)
+{
+        unsigned long nr = sc->nr_to_scan;
+        int contention = 0;
+        unsigned long freed;
+        long clean_zn_cnt = atomic_long_read(&ubifs_clean_zn_cnt);
 
         if (!clean_zn_cnt) {
                 /*
@@ -316,10 +323,10 @@ int ubifs_shrinker(struct shrinker *shrink, struct shrink_control *sc)
 
         if (!freed && contention) {
                 dbg_tnc("freed nothing, but contention");
-                return -1;
+                return SHRINK_STOP;
         }
 
 out:
-        dbg_tnc("%d znodes were freed, requested %d", freed, nr);
+        dbg_tnc("%lu znodes were freed, requested %lu", freed, nr);
         return freed;
 }
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 879b9976c12b..3e4aa7281e04 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -49,7 +49,8 @@ struct kmem_cache *ubifs_inode_slab;
 
 /* UBIFS TNC shrinker description */
 static struct shrinker ubifs_shrinker_info = {
-        .shrink = ubifs_shrinker,
+        .scan_objects = ubifs_shrink_scan,
+        .count_objects = ubifs_shrink_count,
         .seeks = DEFAULT_SEEKS,
 };
 
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index b2babce4d70f..e8c8cfe1435c 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1624,7 +1624,10 @@ int ubifs_tnc_start_commit(struct ubifs_info *c, struct ubifs_zbranch *zroot);
 int ubifs_tnc_end_commit(struct ubifs_info *c);
 
 /* shrinker.c */
-int ubifs_shrinker(struct shrinker *shrink, struct shrink_control *sc);
+unsigned long ubifs_shrink_scan(struct shrinker *shrink,
+                                struct shrink_control *sc);
+unsigned long ubifs_shrink_count(struct shrinker *shrink,
+                                 struct shrink_control *sc);
 
 /* commit.c */
 int ubifs_bg_thread(void *info);