Re: [PATCH] block: Don't access request after it might be freed

Jens Axboe
2012-11-22T20:09:34Z

On 2012-11-22 11:00, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
>
> After we've done __elv_add_request() and __blk_run_queue() in
> blk_execute_rq_nowait(), the request might finish and be freed
> immediately. Therefore checking if the type is REQ_TYPE_PM_RESUME
> isn't safe afterwards, because if it isn't, rq might be gone.
> Instead, check beforehand and stash the result in a temporary.
>
> This fixes crashes in blk_execute_rq_nowait() I get occasionally when
> running with lots of memory debugging options enabled -- I think this
> race is usually harmless because the window for rq to be reallocated
> is so small.

Thanks Roland, that's obviously a bug, not safe to touch the request
even after insertion, let alone running the queue. Applied.

--
Jens Axboe