failslab: add ability to filter slab caches

This patch allow to inject faults only for specific slabs.
In order to preserve default behavior cache filter is off by
default (all caches are faulty).

One may define specific set of slabs like this:
# mark skbuff_head_cache as faulty
echo 1 > /sys/kernel/slab/skbuff_head_cache/failslab
# Turn on cache filter (off by default)
echo 1 > /sys/kernel/debug/failslab/cache-filter
# Turn on fault injection
echo 1 > /sys/kernel/debug/failslab/times
echo 1 > /sys/kernel/debug/failslab/probability

Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

1 files changed, 27 insertions, 2 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 8d71aaf888d7..cab5288736c8 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -151,7 +151,8 @@
  * Set of flags that will prevent slab merging
  */
 #define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
-                SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE)
+                SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
+                SLAB_FAILSLAB)
 
 #define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
                 SLAB_CACHE_DMA | SLAB_NOTRACK)
@@ -1020,6 +1021,9 @@ static int __init setup_slub_debug(char *str)
                 case 't':
                         slub_debug |= SLAB_TRACE;
                         break;
+                case 'a':
+                        slub_debug |= SLAB_FAILSLAB;
+                        break;
                 default:
                         printk(KERN_ERR "slub_debug option '%c' "
                                 "unknown. skipped\n", *str);
@@ -1718,7 +1722,7 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
         lockdep_trace_alloc(gfpflags);
         might_sleep_if(gfpflags & __GFP_WAIT);
 
-        if (should_failslab(s->objsize, gfpflags))
+        if (should_failslab(s->objsize, gfpflags, s->flags))
                 return NULL;
 
         local_irq_save(flags);
@@ -4171,6 +4175,23 @@ static ssize_t trace_store(struct kmem_cache *s, const char *buf,
 }
 SLAB_ATTR(trace);
 
+#ifdef CONFIG_FAILSLAB
+static ssize_t failslab_show(struct kmem_cache *s, char *buf)
+{
+        return sprintf(buf, "%d\n", !!(s->flags & SLAB_FAILSLAB));
+}
+
+static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
+                                                        size_t length)
+{
+        s->flags &= ~SLAB_FAILSLAB;
+        if (buf[0] == '1')
+                s->flags |= SLAB_FAILSLAB;
+        return length;
+}
+SLAB_ATTR(failslab);
+#endif
+
 static ssize_t reclaim_account_show(struct kmem_cache *s, char *buf)
 {
         return sprintf(buf, "%d\n", !!(s->flags & SLAB_RECLAIM_ACCOUNT));
@@ -4467,6 +4488,10 @@ static struct attribute *slab_attrs[] = {
         &deactivate_remote_frees_attr.attr,
         &order_fallback_attr.attr,
 #endif
+#ifdef CONFIG_FAILSLAB
+        &failslab_attr.attr,
+#endif
+
         NULL
 };