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From: Paolo Bonzini <pbonzini@redhat.com>
To: Christoph Hellwig <hch@lst.de>, Bart Van Assche <bvanassche@acm.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org, Daniel Wagner <dwagner@suse.de>,
	emilne@redhat.com, linux-block@vger.kernel.org,
	dm-devel@redhat.com, nkoenig@redhat.com,
	Martin Wilck <mwilck@suse.com>,
	Alasdair G Kergon <agk@redhat.com>
Subject: Re: [dm-devel] [PATCH v4 1/3] scsi: scsi_ioctl: export __scsi_result_to_blk_status()
Date: Tue, 6 Jul 2021 18:40:00 +0200	[thread overview]
Message-ID: <f96bf6c9-d7a3-bfdc-a645-b6b070f9e9cc@redhat.com> (raw)
In-Reply-To: <20210701061901.GA22293@lst.de>

On 01/07/21 08:19, Christoph Hellwig wrote:
> http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/scsi-ioctl
> 
> But more importantly, dm has no business interpreting the errors.  Just
> like how SG_IO processing generally does not look at the error and
> just returns it to userspace and leaves error handling to the caller
> so should be the decision to resubmit it in a multi-path setup.

The problem is that userspace does not have a way to direct the command 
to a different path in the resubmission.  It may not even have 
permission to issue DM_TABLE_STATUS, or to access the /dev nodes for the 
underlying paths, so without Martin's patches SG_IO on dm-mpath is 
basically unreliable by design.

Paolo

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  reply	other threads:[~2021-07-06 16:40 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-28  9:52 [dm-devel] [PATCH v4 0/3] scsi/dm: dm_blk_ioctl(): implement failover for SG_IO on dm-multipath mwilck
2021-06-28  9:52 ` [dm-devel] [PATCH v4 1/3] scsi: scsi_ioctl: export __scsi_result_to_blk_status() mwilck
2021-06-28  9:53   ` Christoph Hellwig
2021-06-28 14:57     ` Martin Wilck
2021-06-29 12:59       ` Christoph Hellwig
2021-06-29 19:23         ` Martin Wilck
2021-06-29 21:23           ` Keith Busch
2021-06-30  8:12             ` Martin Wilck
2021-06-30 16:01               ` Mike Snitzer
2021-06-30 16:54                 ` Martin Wilck
2021-06-30 22:08                   ` Bart Van Assche
2021-07-01  6:19                     ` Christoph Hellwig
2021-07-06 16:40                       ` Paolo Bonzini [this message]
2021-06-28  9:52 ` [dm-devel] [PATCH v4 2/3] scsi: scsi_ioctl: add sg_io_to_blk_status() mwilck
2021-06-28 14:39   ` kernel test robot
2021-06-29  7:00   ` [dm-devel] [kbuild] " Dan Carpenter
2021-06-28  9:52 ` [dm-devel] [PATCH v4 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO mwilck

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