shrinker: Kill old ->shrink API.

There are no more users of this API, so kill it dead, dead, dead and
quietly bury the corpse in a shallow, unmarked grave in a dark forest deep
in the hills...

[glommer@openvz.org: added flowers to the grave]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Reviewed-by: Greg Thelen <gthelen@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
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, 15 insertions, 45 deletions

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 8f80f243fed9..68c097077ef0 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -7,14 +7,15 @@
  *
  * The 'gfpmask' refers to the allocation we are currently trying to
  * fulfil.
- *
- * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
- * querying the cache size, so a fastpath for that case is appropriate.
  */
 struct shrink_control {
         gfp_t gfp_mask;
 
-        /* How many slab objects shrinker() should scan and try to reclaim */
+        /*
+         * How many objects scan_objects should scan and try to reclaim.
+         * This is reset before every call, so it is safe for callees
+         * to modify.
+         */
         unsigned long nr_to_scan;
 
         /* shrink from these nodes */
@@ -27,11 +28,6 @@ struct shrink_control {
 /*
  * A callback you can register to apply pressure to ageable caches.
  *
- * @shrink() should look through the least-recently-used 'nr_to_scan' entries
- * and attempt to free them up.  It should return the number of objects which
- * remain in the cache.  If it returns -1, it means it cannot do any scanning at
- * this time (eg. there is a risk of deadlock).
- *
  * @count_objects should return the number of freeable items in the cache. If
  * there are no objects to free or the number of freeable items cannot be
  * determined, it should return 0. No deadlock checks should be done during the
@@ -50,7 +46,6 @@ struct shrink_control {
  * @flags determine the shrinker abilities, like numa awareness
  */
 struct shrinker {
-        int (*shrink)(struct shrinker *, struct shrink_control *sc);
         unsigned long (*count_objects)(struct shrinker *,
                                        struct shrink_control *sc);
         unsigned long (*scan_objects)(struct shrinker *,
diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index 63cfcccaebb3..132a985aba8b 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -202,7 +202,7 @@ TRACE_EVENT(mm_shrink_slab_start,
 
         TP_fast_assign(
                 __entry->shr = shr;
-                __entry->shrink = shr->shrink;
+                __entry->shrink = shr->scan_objects;
                 __entry->nr_objects_to_shrink = nr_objects_to_shrink;
                 __entry->gfp_flags = sc->gfp_mask;
                 __entry->pgs_scanned = pgs_scanned;
@@ -241,7 +241,7 @@ TRACE_EVENT(mm_shrink_slab_end,
 
         TP_fast_assign(
                 __entry->shr = shr;
-                __entry->shrink = shr->shrink;
+                __entry->shrink = shr->scan_objects;
                 __entry->unused_scan = unused_scan_cnt;
                 __entry->new_scan = new_scan_cnt;
                 __entry->retval = shrinker_retval;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 799ebceeb4f7..e36454220614 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -194,14 +194,6 @@ void unregister_shrinker(struct shrinker *shrinker)
 }
 EXPORT_SYMBOL(unregister_shrinker);
 
-static inline int do_shrinker_shrink(struct shrinker *shrinker,
-                                     struct shrink_control *sc,
-                                     unsigned long nr_to_scan)
-{
-        sc->nr_to_scan = nr_to_scan;
-        return (*shrinker->shrink)(shrinker, sc);
-}
-
 #define SHRINK_BATCH 128
 
 static unsigned long
@@ -218,10 +210,7 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
         long batch_size = shrinker->batch ? shrinker->batch
                                           : SHRINK_BATCH;
 
-        if (shrinker->count_objects)
-                max_pass = shrinker->count_objects(shrinker, shrinkctl);
-        else
-                max_pass = do_shrinker_shrink(shrinker, shrinkctl, 0);
+        max_pass = shrinker->count_objects(shrinker, shrinkctl);
         if (max_pass == 0)
                 return 0;
 
@@ -240,7 +229,7 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
         if (total_scan < 0) {
                 printk(KERN_ERR
                 "shrink_slab: %pF negative objects to delete nr=%ld\n",
-                       shrinker->shrink, total_scan);
+                       shrinker->scan_objects, total_scan);
                 total_scan = max_pass;
         }
 
@@ -272,27 +261,13 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
                                 max_pass, delta, total_scan);
 
         while (total_scan >= batch_size) {
+                unsigned long ret;
 
-                if (shrinker->scan_objects) {
-                        unsigned long ret;
-                        shrinkctl->nr_to_scan = batch_size;
-                        ret = shrinker->scan_objects(shrinker, shrinkctl);
-
-                        if (ret == SHRINK_STOP)
-                                break;
-                        freed += ret;
-                } else {
-                        int nr_before;
-                        long ret;
-
-                        nr_before = do_shrinker_shrink(shrinker, shrinkctl, 0);
-                        ret = do_shrinker_shrink(shrinker, shrinkctl,
-                                                        batch_size);
-                        if (ret == -1)
-                                break;
-                        if (ret < nr_before)
-                                freed += nr_before - ret;
-                }
+                shrinkctl->nr_to_scan = batch_size;
+                ret = shrinker->scan_objects(shrinker, shrinkctl);
+                if (ret == SHRINK_STOP)
+                        break;
+                freed += ret;
 
                 count_vm_events(SLABS_SCANNED, batch_size);
                 total_scan -= batch_size;