From: Jens Axboe <axboe@kernel.dk>
To: Kashyap Desai <kashyap.desai@broadcom.com>,
Ming Lei <ming.lei@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>,
linux-block <linux-block@vger.kernel.org>,
linux-scsi <linux-scsi@vger.kernel.org>,
Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>,
Sreekanth Reddy <sreekanth.reddy@broadcom.com>,
Sathya Prakash Veerichetty <sathya.prakash@broadcom.com>
Subject: Re: +AFs-PATCH+AF0- blk-mq: Set request mapping to NULL in blk+AF8-mq+AF8-put+AF8-driver+AF8-tag
Date: Thu, 6 Dec 2018 08:22:18 -0700 [thread overview]
Message-ID: <b7a44ebf-8996-aee3-3aaf-2ca18622d161@kernel.dk> (raw)
In-Reply-To: <9e57309d7f40c35c1096b6f932c02f68@mail.gmail.com>
On 12/5/18 10:45 PM, Kashyap Desai wrote:
>>
>> If the 'tag' passed to scsi_host_find_tag() is valid, I think there
>> shouldn't have such issue.
>>
>> If you want to find outstanding IOs, maybe you can try
>> blk_mq_queue_tag_busy_iter()
>> or blk_mq_tagset_busy_iter(), because you may not know if the passed
> 'tag'
>> to
>> scsi_host_find_tag() is valid or not.
>
> We tried quick change in mpt3sas driver using blk_mq_tagset_busy_iter and
> it returns/callback for valid requests (no stale entries are returned).
> Expected.
> Above two APIs are only for blk-mq. What about non-mq case ? Driver
> should use scsi_host_find_tag for non-mq and blk_mq_tagset_busy_iter for
> blk-mq case ?
> I don't see that will be good interface. Also, blk_mq_tagset_busy_iter API
> does not provide control if driver wants to quit in-between or do some
> retry logic etc.
>
> Why can't we add single API which provides the correct output.
From 4.21 and forward, there will only be blk/scsi-mq. This is exactly
the problem with having to maintain two stacks, it's a huge pain.
--
Jens Axboe
next prev parent reply other threads:[~2018-12-06 15:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 10:00 [PATCH] blk-mq: Set request mapping to NULL in blk_mq_put_driver_tag Kashyap Desai
2018-12-04 11:35 ` Ming Lei
2018-12-04 16:51 ` Kashyap Desai
2018-12-04 14:48 ` Bart Van Assche
2018-12-04 16:47 ` Kashyap Desai
2018-12-04 17:14 ` Bart Van Assche
2018-12-04 18:18 ` +AFs-PATCH+AF0- blk-mq: Set request mapping to NULL in blk+AF8-mq+AF8-put+AF8-driver+AF8-tag Kashyap Desai
2018-12-04 19:35 ` Bart Van Assche
2018-12-06 0:33 ` Ming Lei
2018-12-06 5:45 ` Kashyap Desai
2018-12-06 15:22 ` Jens Axboe [this message]
2018-12-07 7:16 ` Kashyap Desai
2018-12-07 10:20 ` Ming Lei
2018-12-07 10:34 ` Kashyap Desai
2018-12-11 15:06 ` Kashyap Desai
2018-12-14 6:22 ` Kashyap Desai
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