From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:34706 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758295AbdEVRut (ORCPT ); Mon, 22 May 2017 13:50:49 -0400 Date: Mon, 22 May 2017 13:50:47 -0400 From: Brian Foster Subject: Re: [PATCH 2/3] xfs: Fix off-by-in in loop termination in xfs_find_get_desired_pgoff() Message-ID: <20170522175045.GB1473@bfoster.bfoster> References: <20170518104850.14508-1-jack@suse.cz> <20170518104850.14508-3-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170518104850.14508-3-jack@suse.cz> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Jan Kara Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org, Eryu Guan On Thu, May 18, 2017 at 12:48:49PM +0200, Jan Kara wrote: > There is an off-by-one error in loop termination conditions in > xfs_find_get_desired_pgoff() since 'end' may index a page beyond end of > desired range if 'endoff' is page aligned. It doesn't have any visible > effects but still it is good to fix it. > > Signed-off-by: Jan Kara > --- > fs/xfs/xfs_file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index f371812e20c6..3714b5736fd3 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1043,7 +1043,7 @@ xfs_find_get_desired_pgoff( > > index = startoff >> PAGE_SHIFT; > endoff = XFS_FSB_TO_B(mp, map->br_startoff + map->br_blockcount); > - end = endoff >> PAGE_SHIFT; > + end = (endoff - 1) >> PAGE_SHIFT; Hmm.. I think this messes with the want count for the pagevec_lookup(). E.g.: # xfs_io -fc "truncate 0" -c "falloc 0 16k" -c "pwrite 0 16k" -c "seek -h 0" /mnt/file wrote 16384/16384 bytes at offset 0 16 KiB, 4 ops; 0.0000 sec (200.321 MiB/sec and 51282.0513 ops/sec) Whence Result HOLE 12288 Brian > do { > int want; > unsigned nr_pages; > -- > 2.12.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html