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>

2 files changed, 27 insertions, 18 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index ee372884c40..f9764e61978 100644
--- a/drivers/md/bcache/btree.c
+++ b/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);
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 12a2c2846f9..4fe6ab2fbe2 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/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,