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 <anton@samba.org>
Acked-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 6805453c18e7..f7210ad6cffd 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -101,6 +101,10 @@ static inline bool fail_stacktrace(struct fault_attr *attr)
 
 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;