Created attachment 468301 [details] Kernel backtrace. With a USB drive with several mounted btrfs filesystems. Remove the drive (without unmounting the filesystems) and then attempt to umount the filesystems manually. Result is a kernel BUG, X appears to exit immediately, and the system does not respond to keyboard. This is with the kernel from bug 656465 (kernel-2.6.36.1-9.bz656465.1.fc15.x86_64). I haven't tested with earlier kernels, due to bug 656465 making it impossible to mount the drive with earlier kernels...
I'll have a look at this one, soon as I get a chance.
(In reply to comment #1) > I'll have a look at this one, soon as I get a chance. This is rather interesting. AFAICT this is due to btrfs not being able to write the device super block(s) prior to umount, the implication being that the file system is possibly corrupt, which is no surprise. I guess the problem is that if we can't do anything to the device then we can't umount or re-mount it and later find out if it's corrupt and possibly repair it. Josef, my first thought is that this would be a case where we would want to mark the fs read only and return success to allow a umount, what do you think?
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