drivers: convert shrinkers to new count/scan API

Convert the driver shrinkers to the new API.  Most changes are compile
tested only because I either don't have the hardware or it's staging
stuff.

FWIW, the md and android code is pretty good, but the rest of it makes me
want to claw my eyes out.  The amount of broken code I just encountered is
mind boggling.  I've added comments explaining what is broken, but I fear
that some of the code would be best dealt with by being dragged behind the
bike shed, burying in mud up to it's neck and then run over repeatedly
with a blunt lawn mower.

Special mention goes to the zcache/zcache2 drivers.  They can't co-exist
in the build at the same time, they are under different menu options in
menuconfig, they only show up when you've got the right set of mm
subsystem options configured and so even compile testing is an exercise in
pulling teeth.  And that doesn't even take into account the horrible,
broken code...

[glommer@openvz.org: fixes for i915, android lowmem, zcache, bcache]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.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>

drivers/gpu/drm/i915/i915_dma.c

@@ -1667,7 +1667,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	return 0;
 
 out_gem_unload:
-	if (dev_priv->mm.inactive_shrinker.shrink)
+	if (dev_priv->mm.inactive_shrinker.scan_objects)
 		unregister_shrinker(&dev_priv->mm.inactive_shrinker);
 
 	if (dev->pdev->msi_enabled)
@@ -1706,7 +1706,7 @@ int i915_driver_unload(struct drm_device *dev)
 
 	i915_teardown_sysfs(dev);
 
-	if (dev_priv->mm.inactive_shrinker.shrink)
+	if (dev_priv->mm.inactive_shrinker.scan_objects)
 		unregister_shrinker(&dev_priv->mm.inactive_shrinker);
 
 	mutex_lock(&dev->struct_mutex);

drivers/gpu/drm/i915/i915_gem.c

@@ -57,10 +57,12 @@ static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
 					 struct drm_i915_fence_reg *fence,
 					 bool enable);
 
-static int i915_gem_inactive_shrink(struct shrinker *shrinker,
-				    struct shrink_control *sc);
+static unsigned long i915_gem_inactive_count(struct shrinker *shrinker,
+					     struct shrink_control *sc);
+static unsigned long i915_gem_inactive_scan(struct shrinker *shrinker,
+					    struct shrink_control *sc);
 static long i915_gem_purge(struct drm_i915_private *dev_priv, long target);
-static void i915_gem_shrink_all(struct drm_i915_private *dev_priv);
+static long i915_gem_shrink_all(struct drm_i915_private *dev_priv);
 static void i915_gem_object_truncate(struct drm_i915_gem_object *obj);
 
 static bool cpu_cache_is_coherent(struct drm_device *dev,
@@ -1736,16 +1738,21 @@ i915_gem_purge(struct drm_i915_private *dev_priv, long target)
 	return __i915_gem_shrink(dev_priv, target, true);
 }
 
-static void
+static long
 i915_gem_shrink_all(struct drm_i915_private *dev_priv)
 {
 	struct drm_i915_gem_object *obj, *next;
+	long freed = 0;
 
 	i915_gem_evict_everything(dev_priv->dev);
 
 	list_for_each_entry_safe(obj, next, &dev_priv->mm.unbound_list,
-				 global_list)
+				 global_list) {
+		if (obj->pages_pin_count == 0)
+			freed += obj->base.size >> PAGE_SHIFT;
 		i915_gem_object_put_pages(obj);
+	}
+	return freed;
 }
 
 static int
@@ -4526,7 +4533,8 @@ i915_gem_load(struct drm_device *dev)
 
 	dev_priv->mm.interruptible = true;
 
-	dev_priv->mm.inactive_shrinker.shrink = i915_gem_inactive_shrink;
+	dev_priv->mm.inactive_shrinker.scan_objects = i915_gem_inactive_scan;
+	dev_priv->mm.inactive_shrinker.count_objects = i915_gem_inactive_count;
 	dev_priv->mm.inactive_shrinker.seeks = DEFAULT_SEEKS;
 	register_shrinker(&dev_priv->mm.inactive_shrinker);
 }
@@ -4749,8 +4757,8 @@ static bool mutex_is_locked_by(struct mutex *mutex, struct task_struct *task)
 #endif
 }
 
-static int
-i915_gem_inactive_shrink(struct shrinker *shrinker, struct shrink_control *sc)
+static unsigned long
+i915_gem_inactive_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
 	struct drm_i915_private *dev_priv =
 		container_of(shrinker,
@@ -4758,9 +4766,8 @@ i915_gem_inactive_shrink(struct shrinker *shrinker, struct shrink_control *sc)
 			     mm.inactive_shrinker);
 	struct drm_device *dev = dev_priv->dev;
 	struct drm_i915_gem_object *obj;
-	int nr_to_scan = sc->nr_to_scan;
 	bool unlock = true;
-	int cnt;
+	unsigned long count;
 
 	if (!mutex_trylock(&dev->struct_mutex)) {
 		if (!mutex_is_locked_by(&dev->struct_mutex, current))
@@ -4772,31 +4779,22 @@ i915_gem_inactive_shrink(struct shrinker *shrinker, struct shrink_control *sc)
 		unlock = false;
 	}
 
-	if (nr_to_scan) {
-		nr_to_scan -= i915_gem_purge(dev_priv, nr_to_scan);
-		if (nr_to_scan > 0)
-			nr_to_scan -= __i915_gem_shrink(dev_priv, nr_to_scan,
-							false);
-		if (nr_to_scan > 0)
-			i915_gem_shrink_all(dev_priv);
-	}
-
-	cnt = 0;
+	count = 0;
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list)
 		if (obj->pages_pin_count == 0)
-			cnt += obj->base.size >> PAGE_SHIFT;
+			count += obj->base.size >> PAGE_SHIFT;
 
 	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_list) {
 		if (obj->active)
 			continue;
 
 		if (obj->pin_count == 0 && obj->pages_pin_count == 0)
-			cnt += obj->base.size >> PAGE_SHIFT;
+			count += obj->base.size >> PAGE_SHIFT;
 	}
 
 	if (unlock)
 		mutex_unlock(&dev->struct_mutex);
-	return cnt;
+	return count;
 }
 
 /* All the new VM stuff */
@@ -4860,6 +4858,40 @@ unsigned long i915_gem_obj_size(struct drm_i915_gem_object *o,
 	return 0;
 }
 
+static unsigned long
+i915_gem_inactive_scan(struct shrinker *shrinker, struct shrink_control *sc)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(shrinker,
+			     struct drm_i915_private,
+			     mm.inactive_shrinker);
+	struct drm_device *dev = dev_priv->dev;
+	int nr_to_scan = sc->nr_to_scan;
+	unsigned long freed;
+	bool unlock = true;
+
+	if (!mutex_trylock(&dev->struct_mutex)) {
+		if (!mutex_is_locked_by(&dev->struct_mutex, current))
+			return 0;
+
+		if (dev_priv->mm.shrinker_no_lock_stealing)
+			return 0;
+
+		unlock = false;
+	}
+
+	freed = i915_gem_purge(dev_priv, nr_to_scan);
+	if (freed < nr_to_scan)
+		freed += __i915_gem_shrink(dev_priv, nr_to_scan,
+							false);
+	if (freed < nr_to_scan)
+		freed += i915_gem_shrink_all(dev_priv);
+
+	if (unlock)
+		mutex_unlock(&dev->struct_mutex);
+	return freed;
+}
+
 struct i915_vma *i915_gem_obj_to_vma(struct drm_i915_gem_object *obj,
 				     struct i915_address_space *vm)
 {

drivers/gpu/drm/ttm/ttm_page_alloc.c

@@ -377,28 +377,26 @@ static int ttm_page_pool_free(struct ttm_page_pool *pool, unsigned nr_free)
 	return nr_free;
 }
 
-/* Get good estimation how many pages are free in pools */
-static int ttm_pool_get_num_unused_pages(void)
-{
-	unsigned i;
-	int total = 0;
-	for (i = 0; i < NUM_POOLS; ++i)
-		total += _manager->pools[i].npages;
-
-	return total;
-}
-
 /**
  * Callback for mm to request pool to reduce number of page held.
+ *
+ * XXX: (dchinner) Deadlock warning!
+ *
+ * ttm_page_pool_free() does memory allocation using GFP_KERNEL.  that means
+ * this can deadlock when called a sc->gfp_mask that is not equal to
+ * GFP_KERNEL.
+ *
+ * This code is crying out for a shrinker per pool....
  */
-static int ttm_pool_mm_shrink(struct shrinker *shrink,
-			      struct shrink_control *sc)
+static unsigned long
+ttm_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	static atomic_t start_pool = ATOMIC_INIT(0);
 	unsigned i;
 	unsigned pool_offset = atomic_add_return(1, &start_pool);
 	struct ttm_page_pool *pool;
 	int shrink_pages = sc->nr_to_scan;
+	unsigned long freed = 0;
 
 	pool_offset = pool_offset % NUM_POOLS;
 	/* select start pool in round robin fashion */
@@ -408,14 +406,28 @@ static int ttm_pool_mm_shrink(struct shrinker *shrink,
 			break;
 		pool = &_manager->pools[(i + pool_offset)%NUM_POOLS];
 		shrink_pages = ttm_page_pool_free(pool, nr_free);
+		freed += nr_free - shrink_pages;
 	}
-	/* return estimated number of unused pages in pool */
-	return ttm_pool_get_num_unused_pages();
+	return freed;
+}
+
+
+static unsigned long
+ttm_pool_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	unsigned i;
+	unsigned long count = 0;
+
+	for (i = 0; i < NUM_POOLS; ++i)
+		count += _manager->pools[i].npages;
+
+	return count;
 }
 
 static void ttm_pool_mm_shrink_init(struct ttm_pool_manager *manager)
 {
-	manager->mm_shrink.shrink = &ttm_pool_mm_shrink;
+	manager->mm_shrink.count_objects = ttm_pool_shrink_count;
+	manager->mm_shrink.scan_objects = ttm_pool_shrink_scan;
 	manager->mm_shrink.seeks = 1;
 	register_shrinker(&manager->mm_shrink);
 }

drivers/gpu/drm/ttm/ttm_page_alloc_dma.c

@@ -918,19 +918,6 @@ int ttm_dma_populate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(ttm_dma_populate);
 
-/* Get good estimation how many pages are free in pools */
-static int ttm_dma_pool_get_num_unused_pages(void)
-{
-	struct device_pools *p;
-	unsigned total = 0;
-
-	mutex_lock(&_manager->lock);
-	list_for_each_entry(p, &_manager->pools, pools)
-		total += p->pool->npages_free;
-	mutex_unlock(&_manager->lock);
-	return total;
-}
-
 /* Put all pages in pages list to correct pool to wait for reuse */
 void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 {
@@ -1002,18 +989,29 @@ EXPORT_SYMBOL_GPL(ttm_dma_unpopulate);
 
 /**
  * Callback for mm to request pool to reduce number of page held.
+ *
+ * XXX: (dchinner) Deadlock warning!
+ *
+ * ttm_dma_page_pool_free() does GFP_KERNEL memory allocation, and so attention
+ * needs to be paid to sc->gfp_mask to determine if this can be done or not.
+ * GFP_KERNEL memory allocation in a GFP_ATOMIC reclaim context woul dbe really
+ * bad.
+ *
+ * I'm getting sadder as I hear more pathetical whimpers about needing per-pool
+ * shrinkers
  */
-static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
-				  struct shrink_control *sc)
+static unsigned long
+ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	static atomic_t start_pool = ATOMIC_INIT(0);
 	unsigned idx = 0;
 	unsigned pool_offset = atomic_add_return(1, &start_pool);
 	unsigned shrink_pages = sc->nr_to_scan;
 	struct device_pools *p;
+	unsigned long freed = 0;
 
 	if (list_empty(&_manager->pools))
-		return 0;
+		return SHRINK_STOP;
 
 	mutex_lock(&_manager->lock);
 	pool_offset = pool_offset % _manager->npools;
@@ -1029,18 +1027,33 @@ static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
 			continue;
 		nr_free = shrink_pages;
 		shrink_pages = ttm_dma_page_pool_free(p->pool, nr_free);
+		freed += nr_free - shrink_pages;
+
 		pr_debug("%s: (%s:%d) Asked to shrink %d, have %d more to go\n",
 			 p->pool->dev_name, p->pool->name, current->pid,
 			 nr_free, shrink_pages);
 	}
 	mutex_unlock(&_manager->lock);
-	/* return estimated number of unused pages in pool */
-	return ttm_dma_pool_get_num_unused_pages();
+	return freed;
+}
+
+static unsigned long
+ttm_dma_pool_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct device_pools *p;
+	unsigned long count = 0;
+
+	mutex_lock(&_manager->lock);
+	list_for_each_entry(p, &_manager->pools, pools)
+		count += p->pool->npages_free;
+	mutex_unlock(&_manager->lock);
+	return count;
 }
 
 static void ttm_dma_pool_mm_shrink_init(struct ttm_pool_manager *manager)
 {
-	manager->mm_shrink.shrink = &ttm_dma_pool_mm_shrink;
+	manager->mm_shrink.count_objects = ttm_dma_pool_shrink_count;
+	manager->mm_shrink.scan_objects = &ttm_dma_pool_shrink_scan;
 	manager->mm_shrink.seeks = 1;
 	register_shrinker(&manager->mm_shrink);
 }

drivers/md/bcache/btree.c

@@ -597,24 +597,19 @@ static int mca_reap(struct btree *b, struct closure *cl, unsigned min_order)
 	return 0;
 }
 
-static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc)
+static unsigned long bch_mca_scan(struct shrinker *shrink,
+				  struct shrink_control *sc)
 {
 	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
 	struct btree *b, *t;
 	unsigned long i, nr = sc->nr_to_scan;
+	unsigned long freed = 0;
 
 	if (c->shrinker_disabled)
-		return 0;
+		return SHRINK_STOP;
 
 	if (c->try_harder)
-		return 0;
-
-	/*
-	 * If nr == 0, we're supposed to return the number of items we have
-	 * cached. Not allowed to return -1.
-	 */
-	if (!nr)
-		return mca_can_free(c) * c->btree_pages;
+		return SHRINK_STOP;
 
 	/* Return -1 if we can't do anything right now */
 	if (sc->gfp_mask & __GFP_WAIT)
@@ -634,14 +629,14 @@ static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc)
 
 	i = 0;
 	list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
-		if (!nr)
+		if (freed >= nr)
 			break;
 
 		if (++i > 3 &&
 		    !mca_reap(b, NULL, 0)) {
 			mca_data_free(b);
 			rw_unlock(true, b);
-			--nr;
+			freed++;
 		}
 	}
 
@@ -652,7 +647,7 @@ static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc)
 	if (list_empty(&c->btree_cache))
 		goto out;
 
-	for (i = 0; nr && i < c->bucket_cache_used; i++) {
+	for (i = 0; (nr--) && i < c->bucket_cache_used; i++) {
 		b = list_first_entry(&c->btree_cache, struct btree, list);
 		list_rotate_left(&c->btree_cache);
 
@@ -661,14 +656,27 @@ static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc)
 			mca_bucket_free(b);
 			mca_data_free(b);
 			rw_unlock(true, b);
-			--nr;
+			freed++;
 		} else
 			b->accessed = 0;
 	}
 out:
-	nr = mca_can_free(c) * c->btree_pages;
 	mutex_unlock(&c->bucket_lock);
-	return nr;
+	return freed;
+}
+
+static unsigned long bch_mca_count(struct shrinker *shrink,
+				   struct shrink_control *sc)
+{
+	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+
+	if (c->shrinker_disabled)
+		return 0;
+
+	if (c->try_harder)
+		return 0;
+
+	return mca_can_free(c) * c->btree_pages;
 }
 
 void bch_btree_cache_free(struct cache_set *c)
@@ -737,7 +745,8 @@ int bch_btree_cache_alloc(struct cache_set *c)
 		c->verify_data = NULL;
 #endif
 
-	c->shrink.shrink = bch_mca_shrink;
+	c->shrink.count_objects = bch_mca_count;
+	c->shrink.scan_objects = bch_mca_scan;
 	c->shrink.seeks = 4;
 	c->shrink.batch = c->btree_pages * 2;
 	register_shrinker(&c->shrink);

drivers/md/bcache/sysfs.c

@@ -556,7 +556,7 @@ STORE(__bch_cache_set)
 		struct shrink_control sc;
 		sc.gfp_mask = GFP_KERNEL;
 		sc.nr_to_scan = strtoul_or_return(buf);
-		c->shrink.shrink(&c->shrink, &sc);
+		c->shrink.scan_objects(&c->shrink, &sc);
 	}
 
 	sysfs_strtoul(congested_read_threshold_us,

drivers/md/dm-bufio.c

@@ -1425,62 +1425,75 @@ static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,
 				unsigned long max_jiffies)
 {
 	if (jiffies - b->last_accessed < max_jiffies)
-		return 1;
+		return 0;
 
 	if (!(gfp & __GFP_IO)) {
 		if (test_bit(B_READING, &b->state) ||
 		    test_bit(B_WRITING, &b->state) ||
 		    test_bit(B_DIRTY, &b->state))
-			return 1;
+			return 0;
 	}
 
 	if (b->hold_count)
-		return 1;
+		return 0;
 
 	__make_buffer_clean(b);
 	__unlink_buffer(b);
 	__free_buffer_wake(b);
 
-	return 0;
+	return 1;
 }
 
-static void __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
-		   struct shrink_control *sc)
+static long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
+		   gfp_t gfp_mask)
 {
 	int l;
 	struct dm_buffer *b, *tmp;
+	long freed = 0;
 
 	for (l = 0; l < LIST_SIZE; l++) {
-		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list)
-			if (!__cleanup_old_buffer(b, sc->gfp_mask, 0) &&
-			    !--nr_to_scan)
-				return;
+		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
+			freed += __cleanup_old_buffer(b, gfp_mask, 0);
+			if (!--nr_to_scan)
+				break;
+		}
 		dm_bufio_cond_resched();
 	}
+	return freed;
 }
 
-static int shrink(struct shrinker *shrinker, struct shrink_control *sc)
+static unsigned long
+dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
-	struct dm_bufio_client *c =
-	    container_of(shrinker, struct dm_bufio_client, shrinker);
-	unsigned long r;
-	unsigned long nr_to_scan = sc->nr_to_scan;
+	struct dm_bufio_client *c;
+	unsigned long freed;
 
+	c = container_of(shrink, struct dm_bufio_client, shrinker);
 	if (sc->gfp_mask & __GFP_IO)
 		dm_bufio_lock(c);
 	else if (!dm_bufio_trylock(c))
-		return !nr_to_scan ? 0 : -1;
+		return SHRINK_STOP;
 
-	if (nr_to_scan)
-		__scan(c, nr_to_scan, sc);
+	freed  = __scan(c, sc->nr_to_scan, sc->gfp_mask);
+	dm_bufio_unlock(c);
+	return freed;
+}
 
-	r = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
-	if (r > INT_MAX)
-		r = INT_MAX;
+static unsigned long
+dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct dm_bufio_client *c;
+	unsigned long count;
 
-	dm_bufio_unlock(c);
+	c = container_of(shrink, struct dm_bufio_client, shrinker);
+	if (sc->gfp_mask & __GFP_IO)
+		dm_bufio_lock(c);
+	else if (!dm_bufio_trylock(c))
+		return 0;
 
-	return r;
+	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
+	dm_bufio_unlock(c);
+	return count;
 }
 
 /*
@@ -1582,7 +1595,8 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	__cache_size_refresh();
 	mutex_unlock(&dm_bufio_clients_lock);
 
-	c->shrinker.shrink = shrink;
+	c->shrinker.count_objects = dm_bufio_shrink_count;
+	c->shrinker.scan_objects = dm_bufio_shrink_scan;
 	c->shrinker.seeks = 1;
 	c->shrinker.batch = 0;
 	register_shrinker(&c->shrinker);
@@ -1669,7 +1683,7 @@ static void cleanup_old_buffers(void)
 			struct dm_buffer *b;
 			b = list_entry(c->lru[LIST_CLEAN].prev,
 				       struct dm_buffer, lru_list);
-			if (__cleanup_old_buffer(b, 0, max_age * HZ))
+			if (!__cleanup_old_buffer(b, 0, max_age * HZ))
 				break;
 			dm_bufio_cond_resched();
 		}

drivers/staging/android/ashmem.c

@@ -341,27 +341,26 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
 /*
  * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab
  *
- * 'nr_to_scan' is the number of objects (pages) to prune, or 0 to query how
- * many objects (pages) we have in total.
+ * 'nr_to_scan' is the number of objects to scan for freeing.
  *
  * 'gfp_mask' is the mask of the allocation that got us into this mess.
  *
- * Return value is the number of objects (pages) remaining, or -1 if we cannot
+ * Return value is the number of objects freed or -1 if we cannot
  * proceed without risk of deadlock (due to gfp_mask).
  *
  * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
  * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
  * pages freed.
  */
-static int ashmem_shrink(struct shrinker *s, struct shrink_control *sc)
+static unsigned long
+ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 {
 	struct ashmem_range *range, *next;
+	unsigned long freed = 0;
 
 	/* We might recurse into filesystem code, so bail out if necessary */
-	if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
-		return -1;
-	if (!sc->nr_to_scan)
-		return lru_count;
+	if (!(sc->gfp_mask & __GFP_FS))
+		return SHRINK_STOP;
 
 	mutex_lock(&ashmem_mutex);
 	list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
@@ -374,17 +373,32 @@ static int ashmem_shrink(struct shrinker *s, struct shrink_control *sc)
 		range->purged = ASHMEM_WAS_PURGED;
 		lru_del(range);
 
-		sc->nr_to_scan -= range_size(range);
-		if (sc->nr_to_scan <= 0)
+		freed += range_size(range);
+		if (--sc->nr_to_scan <= 0)
 			break;
 	}
 	mutex_unlock(&ashmem_mutex);
+	return freed;
+}
 
+static unsigned long
+ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	/*
+	 * note that lru_count is count of pages on the lru, not a count of
+	 * objects on the list. This means the scan function needs to return the
+	 * number of pages freed, not the number of objects scanned.
+	 */
 	return lru_count;
 }
 
 static struct shrinker ashmem_shrinker = {
-	.shrink = ashmem_shrink,
+	.count_objects = ashmem_shrink_count,
+	.scan_objects = ashmem_shrink_scan,
+	/*
+	 * XXX (dchinner): I wish people would comment on why they need on
+	 * significant changes to the default value here
+	 */
 	.seeks = DEFAULT_SEEKS * 4,
 };
 
@@ -690,14 +704,11 @@ static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if (capable(CAP_SYS_ADMIN)) {
 			struct shrink_control sc = {
 				.gfp_mask = GFP_KERNEL,
-				.nr_to_scan = 0,
+				.nr_to_scan = LONG_MAX,
 			};
 
 			nodes_setall(sc.nodes_to_scan);
-
-			ret = ashmem_shrink(&ashmem_shrinker, &sc);
-			sc.nr_to_scan = ret;
-			ashmem_shrink(&ashmem_shrinker, &sc);
+			ashmem_shrink_scan(&ashmem_shrinker, &sc);
 		}
 		break;
 	}

drivers/staging/android/lowmemorykiller.c

@@ -66,11 +66,20 @@ static unsigned long lowmem_deathpending_timeout;
 			pr_info(x);			\
 	} while (0)
 
-static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
+static unsigned long lowmem_count(struct shrinker *s,
+				  struct shrink_control *sc)
+{
+	return global_page_state(NR_ACTIVE_ANON) +
+		global_page_state(NR_ACTIVE_FILE) +
+		global_page_state(NR_INACTIVE_ANON) +
+		global_page_state(NR_INACTIVE_FILE);
+}
+
+static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 {
 	struct task_struct *tsk;
 	struct task_struct *selected = NULL;
-	int rem = 0;
+	unsigned long rem = 0;
 	int tasksize;
 	int i;
 	short min_score_adj = OOM_SCORE_ADJ_MAX + 1;
@@ -92,19 +101,17 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 			break;
 		}
 	}
-	if (sc->nr_to_scan > 0)
-		lowmem_print(3, "lowmem_shrink %lu, %x, ofree %d %d, ma %hd\n",
-				sc->nr_to_scan, sc->gfp_mask, other_free,
-				other_file, min_score_adj);
-	rem = global_page_state(NR_ACTIVE_ANON) +
-		global_page_state(NR_ACTIVE_FILE) +
-		global_page_state(NR_INACTIVE_ANON) +
-		global_page_state(NR_INACTIVE_FILE);
-	if (sc->nr_to_scan <= 0 || min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
-		lowmem_print(5, "lowmem_shrink %lu, %x, return %d\n",
-			     sc->nr_to_scan, sc->gfp_mask, rem);
-		return rem;
+
+	lowmem_print(3, "lowmem_scan %lu, %x, ofree %d %d, ma %hd\n",
+			sc->nr_to_scan, sc->gfp_mask, other_free,
+			other_file, min_score_adj);
+
+	if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
+		lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
+			     sc->nr_to_scan, sc->gfp_mask);
+		return 0;
 	}
+
 	selected_oom_score_adj = min_score_adj;
 
 	rcu_read_lock();
@@ -154,16 +161,18 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 		lowmem_deathpending_timeout = jiffies + HZ;
 		send_sig(SIGKILL, selected, 0);
 		set_tsk_thread_flag(selected, TIF_MEMDIE);
-		rem -= selected_tasksize;
+		rem += selected_tasksize;
 	}
-	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
+
+	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
 		     sc->nr_to_scan, sc->gfp_mask, rem);
 	rcu_read_unlock();
 	return rem;
 }
 
 static struct shrinker lowmem_shrinker = {
-	.shrink = lowmem_shrink,
+	.scan_objects = lowmem_scan,
+	.count_objects = lowmem_count,
 	.seeks = DEFAULT_SEEKS * 16
 };