On Thu, Nov 02, 2023 at 03:54:48PM +0100, Christian Brauner wrote: > On Thu, Nov 02, 2023 at 06:06:10PM +0530, Chandan Babu R wrote: > > Hi, > > > > generic/311 consistently fails when executing on a kernel built from > > next-20231102. > > > > The following is the fstests config file that was used during testing. > > > > export FSTYP=xfs > > > > export TEST_DEV=/dev/loop0 > > export TEST_DIR=/mnt/test > > export TEST_LOGDEV=/dev/loop2 > > > > export SCRATCH_DEV=/dev/loop1 > > export SCRATCH_MNT=/mnt/scratch > > export SCRATCH_LOGDEV=/dev/loop3 > > Thanks for the report. So dm flakey sets up: > > /dev/dm-0 over /dev/loop0 > /dev/dm-1 over /dev/loop2 > > and then we mount an xfs filesystem with: > > /dev/loop2 as logdev and /dev/loop0 as the main device. > > So on current kernels what happens is that if you freeze the main > device you end up: > > bdev_freeze(dm-0) > -> get_super(dm-0) # finds xfs sb > -> freeze_super(sb) > > if you also freeze the log device afterwards via: > > bdev_freeze(dm-1) > -> get_super(dm-1) # doesn't find xfs sb because freezing only works for > # main device > > What's currently in -next allows you to roughly do the following: > > bdev_freeze(dm-0) > -> fs_bdev_freeze(dm-0->sb) > -> freeze_super(dm-0->sb) # returns 0 > > bdev_freeze(dm-1) > -> fs_bdev_freeze(dm-1->sb) > -> freeze_super(dm-1->sb) # returns -EBUSY > > So you'll see EBUSY because the superblock was already frozen when the > main block device was frozen. I was somewhat expecting that we may run > into such issues. > > I think we just need to figure out what we want to do in cases the > superblock is frozen via multiple devices. It would probably be correct > to keep it frozen as long as any of the devices is frozen? So this series removed the blockdev freeze nesting code that dm suspend/resume functionality used (i.e. it allowed concurrent bdev freeze/thaw works and leaves the bdev frozen until the last thaw occurs). Removing bd_fsfreeze_count essentially removed this nesting ability. IMO, bdev_freeze() should still nest freeze/thaw across all devices in the filesystem like it used to on the main device. This implies that freeze_super() needs to know that it is being called from bdev_freeze() and needs a freeze counter to allow concurrent bdev freezes and only thaw the fs when the last freeze goes away.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
