[patch 3/7] fault-injection capability for kmalloc

Akinobu Mita
2006-10-12T07:45:04Z

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From: Akinobu Mita <akinobu.mita@gmail.com>

This patch provides fault-injection capability for kmalloc.

Boot option:

failslab=<interval>,<probability>,<space>,<times>

<interval> -- specifies the interval of failures.

<probability> -- specifies how often it should fail in percent.

<space> -- specifies the size of free space where memory can be
allocated safely in bytes.

<times> -- specifies how many times failures may happen at most.

Debugfs:

/debug/failslab/interval
/debug/failslab/probability
/debug/failslab/specifies
/debug/failslab/times

Example:

failslab=10,100,0,-1

slab allocation (kmalloc(), kmem_cache_alloc(),..) fails once per 10 times.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>

lib/Kconfig.debug | 7 +++++++
mm/slab.c | 43 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)

Index: work-fault-inject/mm/slab.c
===================================================================
--- work-fault-inject.orig/mm/slab.c
+++ work-fault-inject/mm/slab.c
@@ -107,6 +107,7 @@
#include <linux/mempolicy.h>
#include <linux/mutex.h>
#include <linux/rtmutex.h>
+#include <linux/fault-inject.h>

#include <asm/uaccess.h>
#include <asm/cacheflush.h>
@@ -3075,12 +3076,54 @@ static void *cache_alloc_debugcheck_afte
#define cache_alloc_debugcheck_after(a,b,objp,d) (objp)
#endif

+#ifdef CONFIG_FAILSLAB
+
+static DEFINE_FAULT_ATTR(failslab);
+
+static int __init setup_failslab(char *str)
+{
+ should_fail_srandom(jiffies);
+
+ return setup_fault_attr(&failslab, str);
+}
+__setup("failslab=", setup_failslab);
+
+static int should_failslab(struct kmem_cache *cachep, gfp_t flags)
+{
+ if ((flags & __GFP_NOFAIL) || cachep == &cache_cache)
+ return 0;
+
+ return should_fail(&failslab, obj_size(cachep));
+}
+
+static int __init failslab_debugfs(void)
+{
+ should_fail_srandom(jiffies);
+
+ return init_fault_attr_entries(&failslab, "failslab");
+}
+
+late_initcall(failslab_debugfs);
+
+#else /* CONFIG_FAILSLAB */
+
+static inline int should_failslab(struct kmem_cache *cachep, gfp_t flags)
+{
+ return 0;
+}
+
+#endif /* CONFIG_FAILSLAB */
+
static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
void *objp;
struct array_cache *ac;

check_irq_off();
+
+ if (should_failslab(cachep, flags))
+ return NULL;
+
ac = cpu_cache_get(cachep);
if (likely(ac->avail)) {
STATS_INC_ALLOCHIT(cachep);
Index: work-fault-inject/lib/Kconfig.debug
===================================================================
--- work-fault-inject.orig/lib/Kconfig.debug
+++ work-fault-inject/lib/Kconfig.debug
@@ -473,6 +473,13 @@ config LKDTM
config FAULT_INJECTION
bool

+config FAILSLAB
+ bool "fault-injection capabilitiy for kmalloc"
+ depends on DEBUG_KERNEL
+ select FAULT_INJECTION
+ help
+ This option provides fault-injection capabilitiy for kmalloc.
+
config FAULT_INJECTION_DEBUG_FS
bool "debugfs entries for fault-injection capabilities"
depends on FAULT_INJECTION && SYSFS

--