2012-06-01 00:49:25

by Anton Blanchard

Subject: [PATCH] fault-inject: Avoid call to random32() if fault injection is disabled

After enabling CONFIG_FAILSLAB I noticed random32 in profiles even
if slub fault injection wasn't enabled at runtime.

should_fail forces a comparison against random32() even if
probability is 0:

if (attr->probability <= random32() % 100)
return false;

Add a check up front for probability == 0 and avoid all of the more
complicated checks.

Signed-off-by: Anton Blanchard <[email protected]>
---

Index: linux-build/lib/fault-inject.c
===================================================================
--- linux-build.orig/lib/fault-inject.c 2012-02-11 21:22:32.303459860 +1100
+++ linux-build/lib/fault-inject.c 2012-02-11 22:38:10.470977505 +1100
@@ -101,6 +101,10 @@ static inline bool fail_stacktrace(struc

bool should_fail(struct fault_attr *attr, ssize_t size)
{
+ /* No need to check any other properties if the probability is 0 */
+ if (attr->probability == 0)
+ return false;
+
if (attr->task_filter && !fail_task(attr, current))
return false;

2012-06-01 12:38:14

by Akinobu Mita

Subject: Re: [PATCH] fault-inject: Avoid call to random32() if fault injection is disabled

2012/6/1 Anton Blanchard <[email protected]>:
>
> After enabling CONFIG_FAILSLAB I noticed random32 in profiles even
> if slub fault injection wasn't enabled at runtime.
>
> should_fail forces a comparison against random32() even if
> probability is 0:
>
> ? ? ? ?if (attr->probability <= random32() % 100)
> ? ? ? ? ? ? ? ?return false;
>
> Add a check up front for probability == 0 and avoid all of the more
> complicated checks.
>
> Signed-off-by: Anton Blanchard <[email protected]>
> ---
>
> Index: linux-build/lib/fault-inject.c
> ===================================================================
> --- linux-build.orig/lib/fault-inject.c 2012-02-11 21:22:32.303459860 +1100
> +++ linux-build/lib/fault-inject.c ? ? ?2012-02-11 22:38:10.470977505 +1100
> @@ -101,6 +101,10 @@ static inline bool fail_stacktrace(struc
>
> ?bool should_fail(struct fault_attr *attr, ssize_t size)
> ?{
> + ? ? ? /* No need to check any other properties if the probability is 0 */
> + ? ? ? if (attr->probability == 0)
> + ? ? ? ? ? ? ? return false;
> +
> ? ? ? ?if (attr->task_filter && !fail_task(attr, current))
> ? ? ? ? ? ? ? ?return false;
>

Looks good to me.

Acked-by: Akinobu Mita <[email protected]>