From: Mike Christie <michaelc@cs.wisc.edu>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] [PATCH 2/5] revert: "blk-mq: blk-mq should free bios in pass through case"
Date: Fri, 04 Oct 2013 12:39:33 -0500 [thread overview]
Message-ID: <524EFD55.4050701@cs.wisc.edu> (raw)
In-Reply-To: <20131004135014.524075942@bombadil.infradead.org>
On 10/4/13 8:49 AM, Christoph Hellwig wrote:
> This patch causes boot failures when using REQ_FLUSH requests. Also the
> following statement in the commit log:
>
> For non mq calls, the block layer will free the bios when
> blk_finish_request is called.
Sorry, messed up function name. I meant blk_end_request*.
For blk_execute_rq_nowait/blk_execute_rq and normal request use, the
lower levels free the bios as they are completed by one of the
blk_finish_request* calls. The caller of of
blk_execute_rq_nowait/blk_execute_rq does not have to worry about
freeing bios. It just frees the request when it is done with it.
>
> For mq calls, the blk mq code wants the caller to do this.
The problem was that Nick's scsi-mq code added a async
blk_mq_execute_rq support and it did not complete bios in the rq->end_io
callback because he most likely expected it to work like the non-mq case
above.
The goal of my patch was to make the underlying behavior and the
function naming similar.
If we can get the the core block code to finish the bios as they are
completed like is done in the non mq case like I was trying to do, then
with your other patches in this set we do not need to have the rq end_io
callbacks have this:
> if (q->mq_ops) {
> - blk_mq_free_request(flush_rq);
> + blk_mq_finish_request(flush_rq, error);
> spin_lock_irqsave(&q->mq_flush_lock, flags);
The block code would free the bios no matter who sent it and mq type,
and the callers of blk_execute* would just call blk_put_request.
next prev parent reply other threads:[~2013-10-04 17:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-04 13:49 [PATCH 0/5] blk-mq fixes and improvements Christoph Hellwig
2013-10-04 13:49 ` [PATCH 1/5] [PATCH 1/5] percpu_counter: fix irq restore in __percpu_counter_add Christoph Hellwig
2013-10-04 13:49 ` [PATCH 2/5] [PATCH 2/5] revert: "blk-mq: blk-mq should free bios in pass through case" Christoph Hellwig
2013-10-04 17:39 ` Mike Christie [this message]
2013-10-05 10:50 ` Christoph Hellwig
2013-10-05 20:20 ` Mike Christie
2013-10-06 15:02 ` Christoph Hellwig
2013-10-04 13:49 ` [PATCH 3/5] [PATCH 3/5] block: remove request ref_count Christoph Hellwig
2013-10-04 13:49 ` [PATCH 4/5] [PATCH 4/5] block: make blk_get/put_request work for blk-mq drivers Christoph Hellwig
2013-10-04 13:49 ` [PATCH 5/5] [PATCH 5/5] block: use blk-exec.c infrastructure for blk-mq Christoph Hellwig
2013-10-04 21:19 ` [PATCH 0/5] blk-mq fixes and improvements Jens Axboe
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