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 Consider my patch withdrawn.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
