linux-kernel - Re: [PATCH] fault-inject: fix wrong should

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Date:   Wed, 2 Aug 2017 12:15:38 +0800
From:   Lu Fengqi <lufq.fnst@...fujitsu.com>
To:     Akinobu Mita <akinobu.mita@...il.com>
CC:     <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] fault-inject: fix wrong should_fail() decision in task
 context

On Wed, Aug 02, 2017 at 09:28:20AM +0900, Akinobu Mita wrote:
>Commit 1203c8e6fb0a ("fault-inject: simplify access check for fail-nth")
>unintentionally broke a conditional statement in should_fail().  Any faults
>are not injected in the task context by the change when the systematic
>fault injection is not used.
>
>This change restores to the previous correct behaviour.
>
>Fixes: 1203c8e6fb0a ("fault-inject: simplify access check for fail-nth")
>Cc: Dmitry Vyukov <dvyukov@...gle.com>
>Cc: Lu Fengqi <lufq.fnst@...fujitsu.com>
>Reported-by: Lu Fengqi <lufq.fnst@...fujitsu.com>
>Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
>---
> lib/fault-inject.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
>diff --git a/lib/fault-inject.c b/lib/fault-inject.c
>index 7d315fd..cf7b129 100644
>--- a/lib/fault-inject.c
>+++ b/lib/fault-inject.c
>@@ -110,10 +110,12 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
> 	if (in_task()) {
> 		unsigned int fail_nth = READ_ONCE(current->fail_nth);
> 
>-		if (fail_nth && !WRITE_ONCE(current->fail_nth, fail_nth - 1))
>-			goto fail;
>+		if (fail_nth) {
>+			if (!WRITE_ONCE(current->fail_nth, fail_nth - 1))
>+				goto fail;
> 
>-		return false;
>+			return false;
>+		}
> 	}
> 
> 	/* No need to check any other properties if the probability is 0 */
>-- 
>2.7.4
>
>
>

With this fix, I can produce the IO ERROR by the fail_make_request.

-- 
Thanks,
Lu