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 <bo.li.liu@xxxxxxxxxx>
> > > ---
> > ....
> > > +_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@xxxxxxxxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe fstests" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
