Re: [PATCH V4 04/12] block: add req flag of REQ_POLL_CTX

From: Hannes Reinecke <hare@suse.de>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
	Jeffle Xu <jefflexu@linux.alibaba.com>,
	Mike Snitzer <snitzer@redhat.com>,
	dm-devel@redhat.com
Subject: Re: [PATCH V4 04/12] block: add req flag of REQ_POLL_CTX
Date: Tue, 30 Mar 2021 08:19:58 +0200	[thread overview]
Message-ID: <57058af9-117d-a781-5e77-835710eb76b4@suse.de> (raw)
In-Reply-To: <20210329152622.173035-5-ming.lei@redhat.com>

On 3/29/21 5:26 PM, Ming Lei wrote:
> Add one req flag REQ_POLL_CTX which will be used in the following patch for
> supporting bio based IO polling.
> 
> Exactly this flag can help us to do:
> 
> 1) request flag is cloned in bio_fast_clone(), so if we mark one FS bio
> as REQ_POLL_CTX, all bios cloned from this FS bio will be marked as
> REQ_POLL_CTX too.
> 
> 2) create per-task io polling context if the bio based queue supports
> polling and the submitted bio is HIPRI. Per-task io poll context will be
> created during submit_bio() before marking this HIPRI bio as REQ_POLL_CTX.
> Then we can avoid to create such io polling context if one cloned bio with
> REQ_POLL_CTX is submitted from another kernel context.
> 
> 3) for supporting bio based io polling, we need to poll IOs from all
> underlying queues of the bio device, this way help us to recognize which
> IO needs to polled in bio based style, which will be applied in
> following patch.
> 
> Reviewed-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   block/blk-core.c          | 28 ++++++++++++++++++++++++++--
>   include/linux/blk_types.h |  4 ++++
>   2 files changed, 30 insertions(+), 2 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer