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Date: Wed, 19 Sep 2018 16:07:31 +0800
From: Ming Lei <ming.lei@redhat.com>
To: "jianchao.wang" <jianchao.w.wang@oracle.com>
Cc: Ming Lei <tom.leiming@gmail.com>, Jens Axboe <axboe@kernel.dk>,
	linux-block <linux-block@vger.kernel.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Christoph Hellwig <hch@lst.de>,
	Bart Van Assche <bart.vanassche@wdc.com>,
	Hannes Reinecke <hare@suse.de>,
	Johannes Thumshirn <jthumshirn@suse.de>,
	Adrian Hunter <adrian.hunter@intel.com>,
	James Bottomley <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Linux SCSI List <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH V3 11/17] SCSI: track pending admin commands
Message-ID: <20180919080730.GC23172@ming.t460p>
References: <CACVXFVMWxXZqQfhAT7KaWP60NE2ACPPOz-9Tuoku_QYxuJuwRg@mail.gmail.com>
 <5c13533d-b1ea-616e-07d0-99d59cf65f8a@oracle.com>
 <20180917113506.GA28349@ming.t460p>
 <1f91bfaf-7b9e-881d-7455-6f04bbb37823@oracle.com>
 <20180918073957.GB4805@ming.t460p>
 <e448f24c-d5d0-17fa-b802-76f407169ff2@oracle.com>
 <20180918075544.GD4805@ming.t460p>
 <8d9049f4-a133-d725-d144-769b2d285660@oracle.com>
 <20180918121515.GA14172@ming.t460p>
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On Wed, Sep 19, 2018 at 11:52:21AM +0800, jianchao.wang wrote:
> Hi Ming
> 
> On 09/18/2018 08:15 PM, Ming Lei wrote:
> > The adminq request can be quisced in the scsi_device level, just as normal IO
> > request, because the scsi_device instance is same with normal IO.
> 
> Yes, the scsi_queue_rq->scsi_prep_state_check could gate things out of.
> 
> > 
> > But in blk-mq level, this admin queue won't be quiesced or frozen at all.
> 
> But the scsi_queue_rq/scsi_request_fn will be invoked, right ?
> 
> This is different from the original implementation.

For legacy path, as you mentioned, scsi_prep_fn() will work, then
scsi_request_fn() won't be called.

For blk-mq, scsi_queue_rq() is always called, and that is a bit
different, but the result is fine given admin request is submitted
much less frequently.

Thanks,
Ming