Hi,

This is the bigger issue, and I'm not very familiar with this code either,
so I'll defer to the experts. Yes, it's a change in behavior, but I think
it makes sense to decrement the bd_fsfreeze_count in this case. Here's why:

If the blockdev is frozen by freeze_bdev while it's being unmounted, the
bd_fsfreeze_count is incremented, but the freeze is ignored. Subsequent
attempts to thaw the device will be ignored but return 0 because the sb
is not found. When the device is mounted again, calls to freeze_bdev
will bypass the call to freeze_super for the newly mounted sb, because
bdev->bd_fsfreeze_count was then incremented from 1 to 2 in freeze_bdev.

	if (++bdev->bd_fsfreeze_count > 1)
		goto done;

So you're freezing the device without really freezing the superblock.
Seems like dangerous behavior to me. The new sb will only be frozen if
a second thaw is done, which gets them back in sync. I suppose we could
say this is acceptable loss, and your number of thaws should match your
freezes, and if they don't: user error. Still, it seems like we should do
something about it, like refuse to mount a frozen device. Perhaps it already
does that; I'll need to do some research.

After some experiments, I've determined that my fears about the count are unfounded.
Consider my patch withdrawn. Sorry for the noise.

Bob Peterson