Hi,
Thank you for your comments.
That's inherently unsafe - you can have multiple unfreezes
running in parallel which seriously screws with the bdev semaphore
count that is used to lock the device due to doing multiple up()s
for every down.
Your timeout thingy guarantee that at some point you will get
multiple up()s occuring due to the timer firing racing with
a thaw ioctl.
If this interface is to be more widely exported, then it needs
a complete revamp of the bdev is locked while it is frozen so
that there is no chance of a double up() ever occuring on the
bd_mount_sem due to racing thaws.....
My patch has the race condition as you said.
I will fix it.
Cheers, Takashi
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