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

Akinobu Mita
2006-11-08T17:47:06Z

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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
/debug/failslab/ignore-gfp-highmem
/debug/failslab/ignore-gfp-wait

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 | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)

Index: 2.6-rc/mm/slab.c
===================================================================
--- 2.6-rc.orig/mm/slab.c
+++ 2.6-rc/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>
@@ -3069,12 +3070,101 @@ static void *cache_alloc_debugcheck_afte
#define cache_alloc_debugcheck_after(a,b,objp,d) (objp)
#endif

+#ifdef CONFIG_FAILSLAB
+
+static struct failslab_attr {
+
+ struct fault_attr attr;
+
+ u32 ignore_gfp_highmem;
+ u32 ignore_gfp_wait;
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+ struct dentry *ignore_gfp_highmem_file;
+ struct dentry *ignore_gfp_wait_file;
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+} failslab = {
+ .attr = FAULT_ATTR_INITIALIZER,
+};
+
+static int __init setup_failslab(char *str)
+{
+ return setup_fault_attr(&failslab.attr, str);
+}
+__setup("failslab=", setup_failslab);
+
+static int should_failslab(struct kmem_cache *cachep, gfp_t flags)
+{
+ if (cachep == &cache_cache)
+ return 0;
+ if (flags & __GFP_NOFAIL)
+ return 0;
+ if (failslab.ignore_gfp_highmem && (flags & __GFP_HIGHMEM))
+ return 0;
+ if (failslab.ignore_gfp_wait && (flags & __GFP_WAIT))
+ return 0;
+
+ return should_fail(&failslab.attr, obj_size(cachep));
+}
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int __init failslab_debugfs(void)
+{
+ mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+ struct dentry *dir;
+ int err;
+
+ err = init_fault_attr_dentries(&failslab.attr, "failslab");
+ if (err)
+ return err;
+ dir = failslab.attr.dentries.dir;
+
+ failslab.ignore_gfp_wait_file =
+ debugfs_create_bool("ignore-gfp-wait", mode, dir,
+ &failslab.ignore_gfp_wait);
+
+ failslab.ignore_gfp_highmem_file =
+ debugfs_create_bool("ignore-gfp-highmem", mode, dir,
+ &failslab.ignore_gfp_highmem);
+
+ if (!failslab.ignore_gfp_wait_file ||
+ !failslab.ignore_gfp_highmem_file) {
+ err = -ENOMEM;
+ debugfs_remove(failslab.ignore_gfp_wait_file);
+ debugfs_remove(failslab.ignore_gfp_highmem_file);
+ cleanup_fault_attr_dentries(&failslab.attr);
+ }
+
+ return err;
+}
+
+late_initcall(failslab_debugfs);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#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: 2.6-rc/lib/Kconfig.debug
===================================================================
--- 2.6-rc.orig/lib/Kconfig.debug
+++ 2.6-rc/lib/Kconfig.debug
@@ -416,6 +416,13 @@ 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

--