Re: Fwd: 4.4-rc2 crash: block related
From: Jens Axboe
Date: Wed Nov 25 2015 - 11:30:50 EST
On 11/25/2015 01:39 AM, Jan Kara wrote:
On Wed 25-11-15 08:27:56, Mika Penttilä wrote:
With recent block layer pull i see a 100% repeatable crash on boot while
mounting roots (ext4 partition on eMMC, with cfq io scheduler).
Thanks for report! After some investigation I found out we allocate
elevator specific data in __get_request() only for non-flush requests. And
this is actually required since the flush machinery uses the space in
struct request for something else. Doh. So my patch is just wrong and not
easy to fix since at the time __get_request() is called we are not sure
whether the flush machinery will be used in the end. Jens, please revert
1b2ff19e6a957b1ef0f365ad331b608af80e932e. Thanks!
I'm somewhat surprised that you can reliably hit the race where flushing
gets disabled for the device just while the request is in flight. But I
guess during boot it makes some sense.
Yeah, that's impressive. I'll revert it and get it sent up before -rc3
is cut.
--
Jens Axboe
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