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, 19 insertions, 6 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 2a3f5ff410cf..e03dd6f2a272 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -811,7 +811,7 @@ EXPORT_SYMBOL(kmalloc_order_trace);
 #define SLABINFO_RIGHTS S_IRUSR
 #endif
 
-void print_slabinfo_header(struct seq_file *m)
+static void print_slabinfo_header(struct seq_file *m)
 {
         /*
          * Output format version, so at least we can change it
@@ -876,7 +876,7 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
         }
 }
 
-int cache_show(struct kmem_cache *s, struct seq_file *m)
+static void cache_show(struct kmem_cache *s, struct seq_file *m)
 {
         struct slabinfo sinfo;
 
@@ -895,7 +895,6 @@ int cache_show(struct kmem_cache *s, struct seq_file *m)
                    sinfo.active_slabs, sinfo.num_slabs, sinfo.shared_avail);
         slabinfo_show_stats(m, s);
         seq_putc(m, '\n');
-        return 0;
 }
 
 static int slab_show(struct seq_file *m, void *p)
@@ -904,10 +903,24 @@ static int slab_show(struct seq_file *m, void *p)
 
         if (p == slab_caches.next)
                 print_slabinfo_header(m);
-        if (!is_root_cache(s))
-                return 0;
-        return cache_show(s, m);
+        if (is_root_cache(s))
+                cache_show(s, m);
+        return 0;
+}
+
+#ifdef CONFIG_MEMCG_KMEM
+int memcg_slab_show(struct seq_file *m, void *p)
+{
+        struct kmem_cache *s = list_entry(p, struct kmem_cache, list);
+        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+
+        if (p == slab_caches.next)
+                print_slabinfo_header(m);
+        if (!is_root_cache(s) && s->memcg_params->memcg == memcg)
+                cache_show(s, m);
+        return 0;
 }
+#endif
 
 /*
  * slabinfo_op - iterator that generates /proc/slabinfo