Re: [PATCH] fs: don't return -EINVAL for successful nested thaw

[Christoph Hellwig]

On Fri, Aug 21, 2026 at 10:54:51AM +0200, Moritz Tanner wrote:
> Reproducer (any kernel since v6.8):
> 
>     dmsetup create dut --table "0 $(blockdev --getsz "$DEV") linear $DEV 0"
>     mkfs.ext4 /dev/mapper/dut
>     mount /dev/mapper/dut /mnt
>     fsfreeze --freeze /mnt      # freeze_ucount == 1
>     dmsetup suspend dut         # bd_fsfreeze_count == 1, ucount == 2
>     dmsetup resume dut          # ucount 2 -> 1, but thaw_super()
>                                 # returns -EINVAL, so bdev_thaw()
>                                 # keeps bd_fsfreeze_count at 1
>     fsfreeze --unfreeze /mnt    # filesystem thaws fine
>     umount /mnt
>     mount /dev/mapper/dut /mnt  # EBUSY, forever

Can you wire this up in xfstests or blktests?