[Xen-devel] Re: domU oom -> xvda1 read-only without any notice?

[Josip Rodin <joy@xxxxxxxxxxxxxx>]

On Wed, Mar 31, 2010 at 09:33:40AM +0200, joy wrote:
> Two days ago a resource-intensive process caused one of my new 2.6.32 domUs
> to crash and burn, so yesterday I recompiled the kernel with debug options
> and retried it. In the early hours of today, after a few hours of running
> the same process, the kernel noticed an OOM again and started killing Apache
> and PostgreSQL. Unfortunately what also happened was that the root partition
> (/dev/xvda1) was somehow marked read-only. I tried to remount it from within
> domU, but I just got:
> 
> % sudo mount -o remount,rw /
> mount: block device /dev/xvda1 is write-protected, mounting read-only
> 
> There are no messages in the kernel log on either the .32 domU or the .26
> dom0. What do I do, other than shutdown and re-create? How does one manually
> 'talk' to blkback to see what's up?

On the dom0 I found /sys/module/blkbk/parameters/{debug_lvl,log_stats}.
Echoing 1 into the latter got me:

[1053818.198356] blkback.1.hda1: oo 22161  |  rd 143219463  |  wr 70692159  |  
br    0
[1053818.556417] blkback.1.hda2: oo 45794  |  rd 41644778  |  wr -2072774999  | 
 br    0
[1053819.957581] blkback.2.hda1: oo 5277  |  rd 35391  |  wr 2396186  |  br    0

[1053828.277147] blkback.1.hda1: oo   0  |  rd  275  |  wr  592  |  br    0
[1053828.802488] blkback.1.hda2: oo   0  |  rd   50  |  wr 22689  |  br    0
[1053835.086327] blkback.2.hda1: oo   0  |  rd    0  |  wr   85  |  br    0

And so on. Another attempt at remount didn't provoke any reaction, and I had
also set debug_lvl.

-- 
     2. That which causes joy or happiness.

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