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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH] blk-mq: setup blk_mq_alloc_data.cmd_flags after submit_bio_checks() is done
Date: Fri, 12 Nov 2021 09:44:41 +0100	[thread overview]
Message-ID: <20211112084441.GA32120@lst.de> (raw)
In-Reply-To: <YY4nv5eQUTOF5Wfv@T590>

On Fri, Nov 12, 2021 at 04:37:19PM +0800, Ming Lei wrote:
> > can only be used for reads, and no fua can be set if the preallocating
> > I/O didn't use fua, etc.
> > 
> > What are the pitfalls of just chanigng cmd_flags?
> 
> Then we need to check cmd_flags carefully, such as hctx->type has to
> be same, flush & passthrough flags has to be same, that said all
> ->cmd_flags used for allocating rqs have to be same with the following
> bio->bi_opf.
> 
> In usual cases, I guess all IOs submitted from same plug batch should be
> same type. If not, we can switch to change cmd_flags.

Jens: is this a limit fitting into your use cases?

I guess as a quick fix this rejecting different flags is probably the
best we can do for now, but I suspect we'll want to eventually relax
them.

  reply	other threads:[~2021-11-12  8:44 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-12  8:11 [PATCH] blk-mq: setup blk_mq_alloc_data.cmd_flags after submit_bio_checks() is done Ming Lei
2021-11-12  8:21 ` Christoph Hellwig
2021-11-12  8:37   ` Ming Lei
2021-11-12  8:44     ` Christoph Hellwig [this message]
2021-11-12 12:47       ` Ming Lei
2021-11-12 13:49         ` Geert Uytterhoeven
2021-11-12 15:47         ` Jens Axboe
2021-11-12 16:05           ` Ming Lei
2021-11-12 16:08             ` Jens Axboe
2021-11-12 16:17               ` Ming Lei
2021-11-12 16:30                 ` Jens Axboe
2021-11-12 15:41       ` Jens Axboe

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