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, 60 insertions, 35 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index bd2a3b40cd12..863bef9f9234 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -377,28 +377,26 @@ out:
         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);
 }
diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index b8b394319b45..7957beeeaf73 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/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);
 }