On Tue, 17 Jul 2012 14:17:21 -0700 Benedict Singer <bzsing@xxxxxxxxx> wrote: > Hi XFS and MD experts, > > I'm experiencing a problem with a setup running XFS on top of an MD > raid. The test I'm running is physically pulling a drive while the > system is running, to simulate hardware failure. When the system is > idle, this works fine; the md subsystem detects the missing drive and > degrades the arrays, and everything keeps running fine. If I pull a > drive while heavy IO activity (mostly if not completely reading) is > happening on the XFS filesystem, then very often the filesystem seems to > "hang" - both processes that were accessing the filesystem at the time > hang, as well as any new ones like 'ls'. Luckily, the kernel noticed the > hung processes and spit a bunch of useful information to syslog. The > relevant snippets are reproduced below, including the messages > indicating that the drive was pulled, along with other XFS/MD raid > information from the system. The filesystem in question is on > /dev/md126, mounted on /var/showstore, and the disk pulled was /dev/sda. > Note that at the time this information was collected, the disk had been > re-inserted and a rebuild was proceeding. > > Is this a bug (seems like a race condition leading to a deadlock?), > and/or is there something to change in the way the system is set up to > mitigate or workaround this? Looks a lot like a bug in md. It is waiting for the metadata to be marked 'dirty', and is waiting forever. 2.6.35 is a very old kernel. It is entirely possible that the bug has been fixed. If you can reproduce with something newer I'd certainly be interested. NeilBrown
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