Re: [PATCH] generic/4[13,62]: restore TEST mount options

[Eryu Guan <eguan@redhat.com>]

On Tue, Oct 31, 2017 at 12:25:51PM +0200, Omer Zilberberg wrote:
> 
> 
> On 10/31/2017 06:37 AM, Eryu Guan wrote:
> > On Tue, Oct 31, 2017 at 07:36:58AM +1100, Dave Chinner wrote:
> >> On Mon, Oct 30, 2017 at 10:08:31AM +0200, Omer Zilberberg wrote:
> >>> These tests locally change the TEST_FS_MOUNT_OPTS/MOUNT_OPTIONS
> >>> environment variables, and run _test_cycle_mount. As a result, following
> >>> tests using the TEST mount point may start with different mount options,
> >>> depending on run order.
> >> I don't think that's the case. The change of the environment
> >> variable should only affect the current test process and it's
> >> children. When the test exits, we go back to the environment of the
> >> check process, where the TEST_FS_MOUNT_OPTS environment variable is
> >> still correctly set, and all future tests inherit from that. i.e.:
> >>
> >> $ export FOO=foo
> >> $ echo $FOO
> >> foo
> >> $ bash
> >> $ echo $FOO
> >> foo
> >> $ export FOO=bar
> >> $ echo $FOO
> >> bar
> >> $ exit
> >> $ echo $FOO
> >> foo
> >> $
> >>
> >> And after each test, check runs _check_filesystems(), which cycles
> >> the test mount, so for each new test process that is run they should
> >> already start in the correct state...
> > I agreed, the changing of variables in a sub-shell won't affect the
> > parent's copy, and check will restore the mounts with the untouched
> > options.
> >
> > But the problem is that _check_test_fs() will cycle mount TEST_DEV with
> > MOUNT_OPTIONS not TEST_FS_MOUNT_OPTS, so if you have different mount
> > options set for TEST_DEV and SCRATCH_DEV, you'll see mount options
> > changed for TEST_DEV. e.g.
> >
> > MOUNT_OPTIONS="-o dax" TEST_FS_MOUNT_OPTS="" ./check generic/413 generic/445
> > generic/445 mount TEST_DEV with "-o dax" too
> >
> > MOUNT_OPTIONS="" TEST_FS_MOUNT_OPTS="-o dax" ./check generic/413 generic/445
> > generic/445 mount TEST_DEV without "-o dax"
> >
> > MOUNT_OPTIONS="-o dax" TEST_FS_MOUNT_OPTS="-o dax" ./check generic/413 generic/445
> > both tests and both devices mount with "-o dax"
> >
> > That's been discussed in this thread:
> > https://patchwork.kernel.org/patch/9742039/
> >
> > Omer, can you please confirm if you're hitting this issue?
> I'm not 100% that's the case, so I better describe my settings more clearly:
> I have a debug mount option on my system to recover the FS from a backup.
> When that flag is set, umount writes everything to the backup.
> Mount restores from it, overwriting everything.

If you're testing with setting your debug mount option to both
TEST_FS_MOUNT_OPTS and MOUNT_OPTIONS, and you still see the failure you
were seeing, then that's a different problem.

> 
> As long as generic/413 is not involved, everything works well.
> All _test_cycle_mount() calls first back everything up on umount,
> then restore upon mount. So I get the same FS contents.
> 
> But, consider generic/118 running after generic/413:
> - generic/413 finishes with a mount point with no mount options
> - generic/118 begins with restored TEST_FS_MOUNT_OPTS, as you've pointed out.
> - some writes are performed to the FS
> - next _test_cycle_mount:
>   calls umount w/o backing up (debug flag previously unset by generic/413).

Does this clear the backup too? If so, I suspect TEST_DEV got cleared on
first mount with the debug option in generic/118, because the backup has
been cleared in the _test_cycle_mount call in generic/413.

>   calls mount WITH the debug flag, and recovers from an empty backup,
>   deleting the earlier writes.
> - subsequent md5sum fails on "No such file or directory", as FS is now empty.
> 
> > I think fixing _check_<fs>_filesystem() is the correct way. And I guess
> > we can refactor out a common function and call it in
> > _check_[xfs|btrfs|generic]_filesystem, pass the correct mount options
> > based on what device we're working on.
> If indeed we're talking about the same problem,
> please let me know if you'd like me to prepare a different patch.

Sure, really appreciated if you can prepare a different patch, even if
it's not the same problem :)

Thanks,
Eryu