memcg: use generic slab iterators for showing slabinfo

Let's use generic slab_start/next/stop for showing memcg caches info.  In
contrast to the current implementation, this will work even if all memcg
caches' info doesn't fit into a seq buffer (a page), plus it simply looks
neater.

Actually, the main reason I do this isn't mere cleanup.  I'm going to zap
the memcg_slab_caches list, because I find it useless provided we have the
slab_caches list, and this patch is a step in this direction.

It should be noted that before this patch an attempt to read
memory.kmem.slabinfo of a cgroup that doesn't have kmem limit set resulted
in -EIO, while after this patch it will silently show nothing except the
header, but I don't think it will frustrate anyone.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 21 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 32e3b191857d..9d30129b0d4a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2547,26 +2547,6 @@ static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
 	return cache_from_memcg_idx(cachep, memcg_cache_id(p->memcg));
 }
 
-#ifdef CONFIG_SLABINFO
-static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
-{
-	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
-	struct memcg_cache_params *params;
-
-	if (!memcg_kmem_is_active(memcg))
-		return -EIO;
-
-	print_slabinfo_header(m);
-
-	mutex_lock(&memcg_slab_mutex);
-	list_for_each_entry(params, &memcg->memcg_slab_caches, list)
-		cache_show(memcg_params_to_cache(params), m);
-	mutex_unlock(&memcg_slab_mutex);
-
-	return 0;
-}
-#endif
-
 static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp,
 			     unsigned long nr_pages)
 {
@@ -4708,7 +4688,10 @@ static struct cftype mem_cgroup_files[] = {
 #ifdef CONFIG_SLABINFO
 	{
 		.name = "kmem.slabinfo",
-		.seq_show = mem_cgroup_slabinfo_read,
+		.seq_start = slab_start,
+		.seq_next = slab_next,
+		.seq_stop = slab_stop,
+		.seq_show = memcg_slab_show,
 	},
 #endif
 #endif