From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933170AbcHNLOj (ORCPT ); Sun, 14 Aug 2016 07:14:39 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51943 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933373AbcHNLBV (ORCPT ); Sun, 14 Aug 2016 07:01:21 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Hugh Dickins" , "Linus Torvalds" Date: Sat, 13 Aug 2016 18:42:51 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 272/305] tmpfs: fix regression hang in fallocate undo In-Reply-To: X-SA-Exim-Connect-IP: 92.40.249.202 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.37-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hugh Dickins commit 7f556567036cb7f89aabe2f0954b08566b4efb53 upstream. The well-spotted fallocate undo fix is good in most cases, but not when fallocate failed on the very first page. index 0 then passes lend -1 to shmem_undo_range(), and that has two bad effects: (a) that it will undo every fallocation throughout the file, unrestricted by the current range; but more importantly (b) it can cause the undo to hang, because lend -1 is treated as truncation, which makes it keep on retrying until every page has gone, but those already fully instantiated will never go away. Big thank you to xfstests generic/269 which demonstrates this. Fixes: b9b4bb26af01 ("tmpfs: don't undo fallocate past its last page") Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: use PAGE_CACHE_SHIFT instead of PAGE_SHIFT] Signed-off-by: Ben Hutchings --- mm/shmem.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1865,9 +1865,11 @@ static long shmem_fallocate(struct file NULL); if (error) { /* Remove the !PageUptodate pages we added */ - shmem_undo_range(inode, - (loff_t)start << PAGE_CACHE_SHIFT, - ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true); + if (index > start) { + shmem_undo_range(inode, + (loff_t)start << PAGE_CACHE_SHIFT, + ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true); + } goto undone; }