linux-kernel - [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG

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Message-ID: <alpine.LNX.2.00.1211131733530.29535@eggly.anvils>
Date:	Tue, 13 Nov 2012 17:36:33 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Dave Jones <davej@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] tmpfs: fix shmem_getpage_gfp VM_BUG_ON fix

We're still hoping to hear back from Dave Jones: but either way,
please fold this patch into the earlier fix for 3.7 and -stable.

Remove its VM_BUG_ON: because either it's as I believe, a tautology
which cannot happen, and does not assert what I'd intended when I put
it in, and would even be wrong if it did (a non-NULL entry can validly
materialize there); or Dave actually hit it on his updated kernel,
in which case more research will be needed, but for upstream we
do not want a user to BUG there.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---

 mm/shmem.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- mmotm/mm/shmem.c	2012-11-09 09:43:46.908046342 -0800
+++ linux/mm/shmem.c	2012-11-13 17:16:38.532528959 -0800
@@ -1158,10 +1158,8 @@ repeat:
 			 * Reset swap.val? No, leave it so "failed" goes back to
 			 * "repeat": reading a hole and writing should succeed.
 			 */
-			if (error) {
-				VM_BUG_ON(error != -ENOENT);
+			if (error)
 				delete_from_swap_cache(page);
-			}
 		}
 		if (error)
 			goto failed;
--
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