linux-kernel - [PATCH] shmem: fix faulting into a hole, not taking i

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Date:	Tue, 22 Jul 2014 17:01:03 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Sasha Levin <sasha.levin@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michel Lespinasse <walken@...gle.com>,
	Lukas Czerner <lczerner@...hat.com>,
	Dave Jones <davej@...hat.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] shmem: fix faulting into a hole, not taking i_mutex: fix

Sasha reports various nasty trinity crashes when shmem_fault() tries
to finish_wait(), we guess from rare cases when the wait_queue_head
on shmem_fallocate()'s stack has already gone.  Fix those by using
TASK_UNINTERRUPIBLE instead of TASK_KILLABLE in prepare_to_wait(),
that's much simpler and safer: TASK_KILLABLE was a nice aspiration,
but not worth any more hassle.

Reported-and-tested-by: Sasha Levin <sasha.levin@...cle.com>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
Andrew, please fold this into
shmem-fix-faulting-into-a-hole-not-taking-i_mutex.patch
before sending the fixes on to Linus - thanks.

 mm/shmem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- mmotm/mm/shmem.c	2014-07-22 16:35:49.683985586 -0700
+++ linux/mm/shmem.c	2014-07-22 16:36:35.459984108 -0700
@@ -1283,7 +1283,7 @@ static int shmem_fault(struct vm_area_st
 
 			shmem_falloc_waitq = shmem_falloc->waitq;
 			prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
-					TASK_KILLABLE);
+					TASK_UNINTERRUPTIBLE);
 			spin_unlock(&inode->i_lock);
 			schedule();
--
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