From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail05.adl6.internode.on.net ([150.101.137.143]:1087 "EHLO ipmail05.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936881AbcCQVIN (ORCPT ); Thu, 17 Mar 2016 17:08:13 -0400 Date: Fri, 18 Mar 2016 08:07:15 +1100 From: Dave Chinner To: Liu Bo Cc: fstests@vger.kernel.org, linux-btrfs@vger.kernel.org Subject: Re: [PATCH v2] fstest: btrfs: test single 4k extent after subpagesize buffered writes Message-ID: <20160317210715.GI11812@dastard> References: <1457394467-1245-1-git-send-email-bo.li.liu@oracle.com> <1457396879-30572-1-git-send-email-bo.li.liu@oracle.com> <20160315033941.GE30721@dastard> <20160317041357.GB29904@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20160317041357.GB29904@localhost.localdomain> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Wed, Mar 16, 2016 at 09:13:57PM -0700, Liu Bo wrote: > On Tue, Mar 15, 2016 at 02:39:41PM +1100, Dave Chinner wrote: > > On Mon, Mar 07, 2016 at 04:27:59PM -0800, Liu Bo wrote: > > > This is to test if COW enabled btrfs can end up with single 4k extents > > > when doing subpagesize buffered writes. > > > > > > Signed-off-by: Liu Bo > > > --- > > .... > > > +_scratch_mkfs >> $seqres.full 2>&1 > > > +_scratch_mount > > > + > > > +default_expire=`cat /proc/sys/vm/dirty_expire_centisecs` > > > +echo 50 > /proc/sys/vm/dirty_expire_centisecs > > > > why? > > Setting it to 50 is to flush dirty pages more frequently so that it's > more likely to reproduce this bug. Explainations should be in comments. .... > > > + $XFS_IO_PROG -c "pwrite $toff $tlen" $tfile > /dev/null 2>&1 > > > + toff=$((toff + tlen)) > > > +done > > > + > > > +sync > > > + > > > +# check for single PAGESIZE extent > > > +$XFS_IO_PROG -c "fiemap -v" $tfile >> $seqres.full 2>&1 > > > +$XFS_IO_PROG -c "fiemap -v" $tfile | awk '{if ($4 == 8) print $4}' > > > > Assumes page size is 4k. Also assumes that no individual extent in > > the file is 4k. Likely broken. > > My miss, will try to come up with a way to tell awk PAGE_SIZE, maybe call getpagesize() ? > (if you already how to do it, please do me a favor :-) ) awk -v pgsize=$page_size \ '{ cnt = pgsize/512; if ($4 == pgsize) print $4; } Assuming that fiemap is reporting in 512 byte block size, not sector sizes... > > > --- /dev/null > > > +++ b/tests/btrfs/027.out > > > @@ -0,0 +1 @@ > > > +QA output created by 027 > > > > So are we expecting no output or not? > > We don't expect any 4k single extent if btrfs is doing correctly, so I leave the output empty. Convention is that we echo a line to the golden output file to document the test is expected to give no output. That's why you see echo "Silence is golden" in many tests... Cheers, Dave. -- Dave Chinner david@fromorbit.com