Hi,
What you *could* do is to start putting processes to sleep if they attempt to write to the frozen filesystem, and then detect the deadlock case where the process holding the file descriptor used to freeze the filesystem gets frozen because it attempted to write to the filesystem --- at which point it gets some kind of signal (which defaults to killing the process), and the filesystem is unfrozen and as part of the unfreeze you wake up all of the processes that were put to sleep for touching the frozen filesystem. The other approach would be to say, "oh well, the freeze ioctl is inherently dangerous, and root is allowed to himself in the foot, so who cares". :-)
Currently the XFS freezer doesn't solve a deadlock automatically and we rely on administrators for ensuring that the freezer will not access the filesystem. And even if the wrong freezer causes a deadlock, it can be solved by other unfreeze process(unfreeze command). So I don't think the freezer itself needs to solve the deadlock. I think the timeout is effective for a unexpected deadlock and the timeout extending feature is very useful as Dmitri proposed. Cheers, Takashi - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
