From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 22 May 2018 09:56:32 +0800
From: Ming Lei <ming.lei@redhat.com>
To: Keith Busch <keith.busch@linux.intel.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Laurence Oberman <loberman@redhat.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	James Smart <james.smart@broadcom.com>,
	linux-nvme@lists.infradead.org, Keith Busch <keith.busch@intel.com>,
	Johannes Thumshirn <jthumshirn@suse.de>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/6] nvme: Sync request queues on reset
Message-ID: <20180522015631.GA20604@ming.t460p>
References: <20180518163823.27820-1-keith.busch@intel.com>
 <20180518223210.GB18334@ming.t460p>
 <20180518234408.GA31749@localhost.localdomain>
 <20180519000141.GB19799@ming.t460p>
 <20180521140413.GA5528@localhost.localdomain>
 <20180521152536.GB19099@ming.t460p>
 <20180521155909.GK5528@localhost.localdomain>
 <20180521160830.GA19858@ming.t460p>
 <20180521162517.GN5528@localhost.localdomain>
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List-ID: <linux-block@vger.kernel.org>

On Mon, May 21, 2018 at 10:25:17AM -0600, Keith Busch wrote:
> On Tue, May 22, 2018 at 12:08:37AM +0800, Ming Lei wrote:
> > Please take a look at blk_mq_complete_request(). Even with Bart's
> > change, the request still won't be completed by driver. The request can
> > only be completed by either driver or blk-mq, not both.
> 
> So you're saying blk-mq can't complete a request the driver returned to
> blk-mq to complete. And that's the nvme driver's problem to fix?

For avoiding use-after-free, one request can only be completed by
one path, either by timeout path or normal completion(irq or cancel)
from driver.

So before handling this req's timeout, this request has to be
marked as completed by blk-mq timeout code already, then nvme_cancel_request()
can't cover this timed-out request.

Thanks,
Ming