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From: Richard Weinberger <richard@nod.at>
To: Christoph Hellwig <hch@lst.de>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-um@lists.infradead.org, dwalter@google.com,
	anton.ivanov@cambridgegreys.com
Subject: Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg
Date: Mon, 15 Oct 2018 23:46:04 +0200	[thread overview]
Message-ID: <48119384.A7YGth2QHM@blindfold> (raw)
In-Reply-To: <20181015205529.GA11086@lst.de>

Am Montag, 15. Oktober 2018, 22:55:29 CEST schrieb Christoph Hellwig:
> On Mon, Oct 15, 2018 at 10:42:47PM +0200, Richard Weinberger wrote:
> > > Sadly not. I'm checking now what exactly is broken.
> > 
> > I take this back. Christoph's fixup makes reading work.
> > The previous version corrupted my test block device in interesting ways
> > and confused all tests.
> > But the removal of blk_rq_map_sg() still has issues.
> > Now the device blocks endless upon flush.
> 
> I suspect we still need to special case flush.  Updated patch below
> including your other suggestion:

While playing further with the patch I managed to hit
BUG_ON(blk_queued_rq(rq)) in blk_mq_requeue_request().

UML requeues the request in ubd_queue_one_vec() if it was not able
to submit the request to the host io-thread.
The fd can return -EAGAIN, then UML has to try later.

Isn't this allowed in that context?

drivers/block/xen-blkfront.c seem to faced the same problem, since
it does a list_del_init(&req->queuelist) right before calling
blk_mq_requeue_request() o_O.

Thanks,
//richard





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  reply	other threads:[~2018-10-15 21:46 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15  6:56 [PATCH, RFC] ubd: remove use of blk_rq_map_sg Christoph Hellwig
2018-10-15  8:40 ` Richard Weinberger
2018-10-15  8:45   ` Christoph Hellwig
2018-10-15 19:17     ` Richard Weinberger
2018-10-15 20:42       ` Richard Weinberger
2018-10-15 20:55         ` Christoph Hellwig
2018-10-15 21:46           ` Richard Weinberger [this message]
2018-10-15 22:04             ` Jens Axboe
2018-10-15 22:44               ` Richard Weinberger
2018-10-16  2:19                 ` Jens Axboe
2018-10-16  8:38                   ` Richard Weinberger
2018-10-16 14:26                     ` Jens Axboe
2018-10-17  6:21                       ` Christoph Hellwig
2018-10-18 21:04                         ` Richard Weinberger
2018-10-15  8:46   ` Anton Ivanov
2018-10-16 22:43 ` Richard Weinberger
2018-10-17  6:14   ` Christoph Hellwig

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