Re: [PATCH 1/2] xfstests: support dm-delay to introduce I/O delays

[Brian Foster <bfoster@redhat.com>]

On Thu, Jun 30, 2016 at 09:19:22PM +0800, Eryu Guan wrote:
> On Thu, Jun 30, 2016 at 08:49:33AM -0400, Brian Foster wrote:
> > Add some infrastructure in common/dmdelay to support use of the dm-delay
> > device-mapper module within tests. This is effectively copied from the
> > existing infrastructure in common/dmflakey. This provides the ability to
> > delay I/O. It only supports delaying read I/O as that is all that is
> > required at this point in time.
> > 
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > ---
> >  common/dmdelay | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 89 insertions(+)
> >  create mode 100644 common/dmdelay
> > 
> > diff --git a/common/dmdelay b/common/dmdelay
> > new file mode 100644
> > index 0000000..c53e2dd
> > --- /dev/null
> > +++ b/common/dmdelay
> > @@ -0,0 +1,89 @@
> > +##/bin/bash
> > +#
> > +# Copyright (c) 2016 Red Hat, Inc.  All Rights Reserved.
> > +#
> > +# This program is free software; you can redistribute it and/or
> > +# modify it under the terms of the GNU General Public License as
> > +# published by the Free Software Foundation.
> > +#
> > +# This program is distributed in the hope that it would be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with this program; if not, write the Free Software Foundation,
> > +# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> > +#
> > +#
> > +# common functions for setting up and tearing down a dmdelay device
> > +
> > +DELAY_NONE=0
> > +DELAY_READ=1
> > +
> > +echo $MOUNT_OPTIONS | grep -q dax
> > +if [ $? -eq 0 ]; then
> > +	_notrun "Cannot run tests with DAX on dmdelay devices"
> > +fi
> > +
> > +_init_delay()
> > +{
> > +	local BLK_DEV_SIZE=`blockdev --getsz $SCRATCH_DEV`
> > +	DELAY_DEV=/dev/mapper/delay-test
> > +	DELAY_TABLE="0 $BLK_DEV_SIZE delay $SCRATCH_DEV 0 0"
> > +	DELAY_TABLE_RDELAY="0 $BLK_DEV_SIZE delay $SCRATCH_DEV 0 10000 $SCRATCH_DEV 0 0"
> > +	$DMSETUP_PROG create delay-test --table "$DELAY_TABLE" || \
> > +		_fatal "failed to create delay device"
> > +	$DMSETUP_PROG mknodes > /dev/null 2>&1
> > +}
> > +
> > +_mount_delay()
> > +{
> > +	_scratch_options mount
> > +	mount -t $FSTYP $SCRATCH_OPTIONS $MOUNT_OPTIONS $DELAY_DEV $SCRATCH_MNT
> 
> I replaced mount with $MOUNT_PROG :)
> 

Thanks.

> > +}
> > +
> > +_unmount_delay()
> > +{
> > +	$UMOUNT_PROG $SCRATCH_MNT
> > +}
> > +
> > +_cleanup_delay()
> > +{
> > +	# If dmsetup load fails then we need to make sure to do resume here
> > +	# otherwise the umount will hang
> > +	$DMSETUP_PROG resume delay-test > /dev/null 2>&1
> > +	$UMOUNT_PROG $SCRATCH_MNT > /dev/null 2>&1
> > +	# wait for device to be fully settled so that 'dmsetup remove' doesn't
> > +	# fail due to EBUSY
> > +	$UDEV_SETTLE_PROG >/dev/null 2>&1
> > +	$DMSETUP_PROG remove delay-test > /dev/null 2>&1
> > +	$DMSETUP_PROG mknodes > /dev/null 2>&1
> > +}
> > +
> > +# _load_delay_table <table> [lockfs]
> > +#
> > +# This defaults to --nolockfs, which doesn't freeze_fs() before loading the new
> > +# table, so it simulates power failure.
> 
> Seems this comment is for dmflakey and needs update. Can you please
> confirm? I can fix it at commit time if needs update, no v2 is needed.
> 

Hmm, the command itself is part of the dmsetup suspend command, but the
power failure bit is probably not relevant since we aren't dropping
I/Os. We could just kill that part of the comment (everything after the
comma)..?

Brian

> Thanks,
> Eryu
> 
> > +_load_delay_table()
> > +{
> > +	table="$DELAY_TABLE"
> > +	[ $1 -eq $DELAY_READ ] && table="$DELAY_TABLE_RDELAY"
> > +
> > +	suspend_opt="--nolockfs"
> > +	[ $# -gt 1 ] && [ $2 -eq 1 ] && suspend_opt=""
> > +
> > +	# run a suspend/resume cycle to avoid excessive resume delays once a
> > +	# delay is introduced below
> > +	$DMSETUP_PROG suspend $suspend_opt delay-test
> > +	$DMSETUP_PROG resume $suspend_opt delay-test
> > +
> > +	$DMSETUP_PROG suspend $suspend_opt delay-test
> > +	[ $? -ne 0 ] && _fatal "failed to suspend delay-test"
> > +
> > +	$DMSETUP_PROG load delay-test --table "$table"
> > +	[ $? -ne 0 ] && _fatal "failed to load table into delay-test"
> > +
> > +	$DMSETUP_PROG resume delay-test
> > +	[ $? -ne 0 ] && _fatal  "failed to resume delay-test"
> > +}
> > -- 
> > 2.5.5
> > 
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