From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 05/15] dm: remove incomple BLOCK_PC support
Date: Thu, 12 Jan 2017 09:00:54 +0100
Message-ID: <20170112080054.GD7567@lst.de>
References: <1484060780-15592-1-git-send-email-hch@lst.de> <1484060780-15592-6-git-send-email-hch@lst.de> <20170112010936.GA19953@redhat.com>
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To: Mike Snitzer <snitzer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@fb.com>, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, dm-devel@redhat.com
List-Id: dm-devel.ids

On Wed, Jan 11, 2017 at 08:09:37PM -0500, Mike Snitzer wrote:
> I'm not following your reasoning.
> 
> dm_blk_ioctl calls __blkdev_driver_ioctl and will call scsi_cmd_ioctl
> (sd_ioctl -> scsi_cmd_blk_ioctl -> scsi_cmd_ioctl) if DM's underlying
> block device is a scsi device.

Yes, it it does.  But scsi_cmd_ioctl as called from sd_ioctl will
operate entirely on the SCSI request_queue - dm-mpath will never see
the BLOCK_PC request generated by it.