slub: disable tracing and failslab for merged slabs

Tracing of mergeable slabs as well as uses of failslab are confusing since the objects of multiple slab caches will be affected. Moreover this creates a situation where a mergeable slab will become unmergeable. If tracing or failslab testing is desired then it may be best to switch merging off for starters. Signed-off-by: Christoph Lameter <[email protected]> Tested-by: WANG Chao <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: David Rientjes <[email protected]> Cc: Joonsoo Kim <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Oct 10, 2014 · c9e1613 · c9e1613
1 parent 25c4f30
commit c9e1613
Showing 1 changed file with 11 additions and 0 deletions.
diff --git a/mm/slub.c b/mm/slub.c
@@ -4604,6 +4604,14 @@ static ssize_t trace_show(struct kmem_cache *s, char *buf)
 static ssize_t trace_store(struct kmem_cache *s, const char *buf,
 							size_t length)
 {
+	/*
+	 * Tracing a merged cache is going to give confusing results
+	 * as well as cause other issues like converting a mergeable
+	 * cache into an umergeable one.
+	 */
+	if (s->refcount > 1)
+		return -EINVAL;
+
 	s->flags &= ~SLAB_TRACE;
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
@@ -4721,6 +4729,9 @@ static ssize_t failslab_show(struct kmem_cache *s, char *buf)
 static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
 							size_t length)
 {
+	if (s->refcount > 1)
+		return -EINVAL;
+
 	s->flags &= ~SLAB_FAILSLAB;
 	if (buf[0] == '1')
 		s->flags |= SLAB_FAILSLAB;