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, 26 insertions, 21 deletions

diff --git a/fs/mbcache.c b/fs/mbcache.c
index 5eb04767cb29..e519e45bf673 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -86,18 +86,6 @@ static LIST_HEAD(mb_cache_list);
 static LIST_HEAD(mb_cache_lru_list);
 static DEFINE_SPINLOCK(mb_cache_spinlock);
 
-/*
- * What the mbcache registers as to get shrunk dynamically.
- */
-
-static int mb_cache_shrink_fn(struct shrinker *shrink,
-                              struct shrink_control *sc);
-
-static struct shrinker mb_cache_shrinker = {
-        .shrink = mb_cache_shrink_fn,
-        .seeks = DEFAULT_SEEKS,
-};
-
 static inline int
 __mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
 {
@@ -151,7 +139,7 @@ forget:
 
 
 /*
- * mb_cache_shrink_fn()  memory pressure callback
+ * mb_cache_shrink_scan()  memory pressure callback
  *
  * This function is called by the kernel memory management when memory
  * gets low.
@@ -159,17 +147,16 @@ forget:
  * @shrink: (ignored)
  * @sc: shrink_control passed from reclaim
  *
- * Returns the number of objects which are present in the cache.
+ * Returns the number of objects freed.
  */
-static int
-mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc)
+static unsigned long
+mb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
         LIST_HEAD(free_list);
-        struct mb_cache *cache;
         struct mb_cache_entry *entry, *tmp;
-        int count = 0;
         int nr_to_scan = sc->nr_to_scan;
         gfp_t gfp_mask = sc->gfp_mask;
+        unsigned long freed = 0;
 
         mb_debug("trying to free %d entries", nr_to_scan);
         spin_lock(&mb_cache_spinlock);
@@ -179,19 +166,37 @@ mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc)
                                    struct mb_cache_entry, e_lru_list);
                 list_move_tail(&ce->e_lru_list, &free_list);
                 __mb_cache_entry_unhash(ce);
+                freed++;
+        }
+        spin_unlock(&mb_cache_spinlock);
+        list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
+                __mb_cache_entry_forget(entry, gfp_mask);
         }
+        return freed;
+}
+
+static unsigned long
+mb_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+        struct mb_cache *cache;
+        unsigned long count = 0;
+
+        spin_lock(&mb_cache_spinlock);
         list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
                 mb_debug("cache %s (%d)", cache->c_name,
                           atomic_read(&cache->c_entry_count));
                 count += atomic_read(&cache->c_entry_count);
         }
         spin_unlock(&mb_cache_spinlock);
-        list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
-                __mb_cache_entry_forget(entry, gfp_mask);
-        }
+
         return vfs_pressure_ratio(count);
 }
 
+static struct shrinker mb_cache_shrinker = {
+        .count_objects = mb_cache_shrink_count,
+        .scan_objects = mb_cache_shrink_scan,
+        .seeks = DEFAULT_SEEKS,
+};
 
 /*
  * mb_cache_create()  create a new cache