I have had single-drive btrfs filesystems lock up on me twice; i.e. file manipulation commands like `ls` freeze and "take forever". In both cases, there was a h

I have had single-drive btrfs filesystems lock up on me twice; i.e. file manipulation commands like `ls` freeze and "take forever". In both cases, there was a hardware failure of the drive. I believe that the frozen processes went into uninterruptible sleep (so they couldn't be killed). It is totally understandable that if the underlying driver starts returning errors, btrfs (or any other filesystem) may be unable to provide access to my data; but I was not at all happy about having to reboot the entire machine. (I must admit, it is possible that the "freezing" was happening in underlying block device driver code and not in btrfs. I don't remember if I ever checked wchan to see which it was. My impression from reading dmesg output was the issue seemed to be with btrfs.) I did once have a similar experience with ZFS as well. Sigh.