Messages in this thread | | | Date | Mon, 23 Mar 2009 10:41:49 +0200 | From | roma1390 <> | Subject | Re: raid6 grow "hangs" on 2.6.27 with mounted FS |
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Neil Brown wrote: > On Saturday March 21, roma1390@gmail.com wrote: > I can almost reproduce this. > However when I run it, the "mdadm --grow" prints mdadm: Need to backup 384K of critical section.. > (as expected) and then hangs. > > If I interrupt it and proceed, then the umount hangs. > > Is this the case for you?
Yes, mdadm hangs by itself, If i start mdadm in background and wait some time for reconstrucion, umount still hangs. I didn't touch mdadm, and mdadm likes to stop...
> The umount hangs because there is something important that mdadm needs > to do which it didn't do because it was interrupted. During the > 'critical section', mdadm causes all writes to the start of the device > to be blocked. The umount tries to write the filesystem superblock > and hangs. > You can test if this is the problem by running the command > > cat /sys/block/md2/md/suspend_hi > /sys/block/md2/md/suspend_lo
First try was:
mdadm --grow /dev/md2 --raid-devices=5 & sleep 3 cat /sys/block/md2/md/suspend_hi # output: 768 cat /sys/block/md2/md/suspend_lo # output: 0 cat /sys/block/md2/md/suspend_hi > /sys/block/md2/md/suspend_lo sleep 20 umount /dev/md2
And this works! mdadm unhangs, and umount doesn't block any more.
> That should allow the 'umount' to complete. > > This will only happen on very small arrays that take less than a > couple of seconds for the reshape to complete. I have a patch for > mdadm which makes it more robust in this situation. It will be in > future releases. > > Does this explain what is happening to you?
Yes, thanks. May be if I retest this situation with same kernel and limited recovery bandwith, then may be i can't hit same problem again?
> Thanks, > NeilBrown
Thanks.
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