From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f197.google.com (mail-ig0-f197.google.com [209.85.213.197]) by kanga.kvack.org (Postfix) with ESMTP id 979A36B0005 for ; Mon, 6 Jun 2016 00:05:08 -0400 (EDT) Received: by mail-ig0-f197.google.com with SMTP id q18so92040048igr.2 for ; Sun, 05 Jun 2016 21:05:08 -0700 (PDT) Received: from mail-oi0-x245.google.com (mail-oi0-x245.google.com. [2607:f8b0:4003:c06::245]) by mx.google.com with ESMTPS id g33si7994936otg.199.2016.06.05.21.05.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 05 Jun 2016 21:05:07 -0700 (PDT) Received: by mail-oi0-x245.google.com with SMTP id s139so139609706oie.0 for ; Sun, 05 Jun 2016 21:05:07 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <5739B60E.1090700@suse.cz> References: <1462713387-16724-1-git-send-email-anthony.romano@coreos.com> <5739B60E.1090700@suse.cz> Date: Sun, 5 Jun 2016 21:05:07 -0700 Message-ID: Subject: Re: [PATCH] tmpfs: don't undo fallocate past its last page From: Brandon Philips Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Anthony Romano , Hugh Dickins , Christoph Hellwig , Cong Wang , Kay Sievers , Andrew Morton , Matthew Garrett Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On Mon, May 16, 2016 at 4:59 AM, Vlastimil Babka wrote: > On 05/08/2016 03:16 PM, Anthony Romano wrote: >> >> When fallocate is interrupted it will undo a range that extends one byte >> past its range of allocated pages. This can corrupt an in-use page by >> zeroing out its first byte. Instead, undo using the inclusive byte range. > > > Huh, good catch. So why is shmem_undo_range() adding +1 to the value in the > first place? The only other caller is shmem_truncate_range() and all *its* > callers do subtract 1 to avoid the same issue. So a nicer fix would be to > remove all this +1/-1 madness. Or is there some subtle corner case I'm > missing? Bumping this thread as I don't think this patch has gotten picked up. And cc'ing folks from 1635f6a74152f1dcd1b888231609d64875f0a81a. Also, resending because I forgot to remove the HTML mime-type to make vger happy. Thank you, Brandon >> Signed-off-by: Anthony Romano > > > Looks like a stable candidate patch. Can you point out the commit that > introduced the bug, for the Fixes: tag? > > Thanks, > Vlastimil > > >> --- >> mm/shmem.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 719bd6b..f0f9405 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -2238,7 +2238,7 @@ static long shmem_fallocate(struct file *file, int >> mode, loff_t offset, >> /* Remove the !PageUptodate pages we added */ >> shmem_undo_range(inode, >> (loff_t)start << PAGE_SHIFT, >> - (loff_t)index << PAGE_SHIFT, true); >> + ((loff_t)index << PAGE_SHIFT) - 1, true); >> goto undone; >> } >> >> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org