sl[au]b: always get the cache from its page in kmem_cache_free()

struct page already has this information.  If we start chaining caches,
this information will always be more trustworthy than whatever is passed
into the function.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <fweisbec@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: JoonSoo Kim <js1304@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Rik van Riel <riel@redhat.com>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 48 insertions, 14 deletions

diff --git a/mm/slab.c b/mm/slab.c
index c26ab9fbe1f5..bab6fec765a7 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -87,7 +87,6 @@
  */
 
 #include        <linux/slab.h>
-#include        "slab.h"
 #include        <linux/mm.h>
 #include        <linux/poison.h>
 #include        <linux/swap.h>
@@ -128,6 +127,8 @@
 
 #include        "internal.h"
 
+#include        "slab.h"
+
 /*
  * DEBUG        - 1 for kmem_cache_create() to honour; SLAB_RED_ZONE & SLAB_POISON.
  *                0 for faster, smaller code (especially in the critical paths).
@@ -3883,6 +3884,9 @@ EXPORT_SYMBOL(__kmalloc);
 void kmem_cache_free(struct kmem_cache *cachep, void *objp)
 {
         unsigned long flags;
+        cachep = cache_from_obj(cachep, objp);
+        if (!cachep)
+                return;
 
         local_irq_save(flags);
         debug_check_no_locks_freed(objp, cachep->object_size);
diff --git a/mm/slab.h b/mm/slab.h
index abe582d20c79..c95e922b166d 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -116,6 +116,13 @@ static inline bool cache_match_memcg(struct kmem_cache *cachep,
         return (is_root_cache(cachep) && !memcg) ||
                                 (cachep->memcg_params->memcg == memcg);
 }
+
+static inline bool slab_equal_or_root(struct kmem_cache *s,
+                                        struct kmem_cache *p)
+{
+        return (p == s) ||
+                (s->memcg_params && (p == s->memcg_params->root_cache));
+}
 #else
 static inline bool is_root_cache(struct kmem_cache *s)
 {
@@ -127,5 +134,37 @@ static inline bool cache_match_memcg(struct kmem_cache *cachep,
 {
         return true;
 }
+
+static inline bool slab_equal_or_root(struct kmem_cache *s,
+                                      struct kmem_cache *p)
+{
+        return true;
+}
 #endif
+
+static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
+{
+        struct kmem_cache *cachep;
+        struct page *page;
+
+        /*
+         * When kmemcg is not being used, both assignments should return the
+         * same value. but we don't want to pay the assignment price in that
+         * case. If it is not compiled in, the compiler should be smart enough
+         * to not do even the assignment. In that case, slab_equal_or_root
+         * will also be a constant.
+         */
+        if (!memcg_kmem_enabled() && !unlikely(s->flags & SLAB_DEBUG_FREE))
+                return s;
+
+        page = virt_to_head_page(x);
+        cachep = page->slab_cache;
+        if (slab_equal_or_root(cachep, s))
+                return cachep;
+
+        pr_err("%s: Wrong slab cache. %s but object is from %s\n",
+                __FUNCTION__, cachep->name, s->name);
+        WARN_ON_ONCE(1);
+        return s;
+}
 #endif
diff --git a/mm/slob.c b/mm/slob.c
index 795bab7d391d..a99fdf7a0907 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -58,7 +58,6 @@
 
 #include <linux/kernel.h>
 #include <linux/slab.h>
-#include "slab.h"
 
 #include <linux/mm.h>
 #include <linux/swap.h> /* struct reclaim_state */
@@ -73,6 +72,7 @@
 
 #include <linux/atomic.h>
 
+#include "slab.h"
 /*
  * slob_block has a field 'units', which indicates size of block if +ve,
  * or offset of next block if -ve (in SLOB_UNITs).
diff --git a/mm/slub.c b/mm/slub.c
index 985332b38852..6d5f2305d7a4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2611,19 +2611,10 @@ redo:
 
 void kmem_cache_free(struct kmem_cache *s, void *x)
 {
-        struct page *page;
-
-        page = virt_to_head_page(x);
-
-        if (kmem_cache_debug(s) && page->slab_cache != s) {
-                pr_err("kmem_cache_free: Wrong slab cache. %s but object"
-                        " is from  %s\n", page->slab_cache->name, s->name);
-                WARN_ON_ONCE(1);
+        s = cache_from_obj(s, x);
+        if (!s)
                 return;
-        }
-
-        slab_free(s, page, x, _RET_IP_);
-
+        slab_free(s, virt_to_head_page(x), x, _RET_IP_);
         trace_kmem_cache_free(_RET_IP_, x);
 }
 EXPORT_SYMBOL(kmem_cache_free);