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Re: [PATCH 2/2] xfstests: Check fs consistency on TEST_DEV only when nee

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 2/2] xfstests: Check fs consistency on TEST_DEV only when needed
From: Lukáš Czerner <lczerner@xxxxxxxxxx>
Date: Thu, 10 Jul 2014 10:38:45 +0200 (CEST)
Cc: fstests@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140710010711.GJ4453@dastard>
References: <1403617014-17870-1-git-send-email-lczerner@xxxxxxxxxx> <1403617014-17870-2-git-send-email-lczerner@xxxxxxxxxx> <20140710010711.GJ4453@dastard>
User-agent: Alpine 2.00 (LFD 1167 2008-08-23)
On Thu, 10 Jul 2014, Dave Chinner wrote:

> Date: Thu, 10 Jul 2014 11:07:11 +1000
> From: Dave Chinner <david@xxxxxxxxxxxxx>
> To: Lukas Czerner <lczerner@xxxxxxxxxx>
> Cc: fstests@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
> Subject: Re: [PATCH 2/2] xfstests: Check fs consistency on TEST_DEV only when
>     needed
> 
> On Tue, Jun 24, 2014 at 03:36:54PM +0200, Lukas Czerner wrote:
> > Currently we're checking file system consistency on TEST_DEV after every
> > successful test run even though the TEST_DEV might not even be used in
> > that test.
> 
> It gets mounted/unmounted for each test, so even if it is not used,
> it might still get modified...
> 
> > Fix it by checking for number of write io on TEST_DEV device before the
> > test and compare it with the value after the test.
> 
> Doesn't work for ram disks:
> 
> # ./setup 
> TEST: DIR=/mnt/test DEV=/dev/ram0 rt=[] log=[]
> TAPE: dev=[] rmt=[] rmtirix=[@]
> SCRATCH: MNT=/mnt/scr DEV=/dev/ram1 rt=[] log=[]
> VARIABLES: external=no largeblk=no fstyp=xfs
>            large_scratch_dev=no attrsecure=no
> # ls -l /dev/ram0
> brw-rw---- 1 root disk 1, 0 Jul  9 15:51 /dev/ram0
> # cat /sys/dev/block/1\:0/stat
>        0        0        0        0        0        0        0        0       
>  0        0        0
> #
> 
> Nor does it work on loop devices.
> 
> > Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> > ---
> >  check     |  6 +++++-
> >  common/rc | 11 +++++++++++
> >  2 files changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/check b/check
> > index 40f99d7..66d0f72 100755
> > --- a/check
> > +++ b/check
> > @@ -544,6 +544,7 @@ for section in $HOST_OPTIONS_SECTIONS; do
> >             rm -f core $seqres.notrun
> >  
> >             scratch_atime=`stat -c %X $SCRATCH_DEV`
> > +           test_write_io=`_get_write_io_count $TEST_DEV`
> >             start=`_wallclock`
> >             $timestamp && echo -n " ["`date "+%T"`"]"
> >             [ ! -x $seq ] && chmod u+x $seq # ensure we can run it
> > @@ -626,7 +627,10 @@ for section in $HOST_OPTIONS_SECTIONS; do
> >         then
> >             try="$try $seqnum"
> >             n_try=`expr $n_try + 1`
> > -           _check_test_fs
> > +           write_io=`_get_write_io_count $TEST_DEV`
> > +           if [ -z $test_write_io ] || [ $write_io -ne $test_write_io ]; 
> > then
> > +                   _check_test_fs
> > +           fi
> 
> Which you work around without mentioning the reason for the zero
> value check. ;)

That's just a safety trigger :) Didn't think it was worth
mentioning.

> 
> Personally, I want the test devices on my systems checked regardless
> of whether the test tries to modify them or not. I, quite frankly,
> don't trust the block device stats because they often get broken or
> are inaccurate. Indeed, there were recent virtio block device
> changes in 3.14-rc1 (or was it 3.15?) that broke the device stats
> and that took several weeks to get fixed properly.
> 
> Hence I don't think using the block device stats for something as
> critical as determining whether we should check a filesystem or not.
> 
> Reducing runtime of the test harness is a good idea, but we should
> not do that if the cost is that it reduces the reliability of error
> detection.

With the patch 1/2 we're going to check scratch dev as well, so if
accepted, the xfstests run time is going to be possibly much longer
especially so on the file systems where fsck time is quite big. So I
think that trying to reduce unnecessary fsck on test_dev is IMO
important.

I like the idea Eric proposed with the _require_test check for the
test that actually require test device and then actually check the
device only after such test. Will that be acceptable ? If so I'll
rework the patches.

Thanks!
-Lukas

> 
> Cheers,
> 
> Dave.
> 

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