From: Christoph Hellwig <hch@lst.de>
To: mwilck@suse.com
Cc: Mike Snitzer <snitzer@redhat.com>,
linux-scsi@vger.kernel.org, Daniel Wagner <dwagner@suse.de>,
emilne@redhat.com, linux-block@vger.kernel.org,
dm-devel@redhat.com, Paolo Bonzini <pbonzini@redhat.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
nkoenig@redhat.com, Bart Van Assche <Bart.VanAssche@sandisk.com>,
Christoph Hellwig <hch@lst.de>,
Alasdair G Kergon <agk@redhat.com>
Subject: Re: [dm-devel] [PATCH v5 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO
Date: Thu, 1 Jul 2021 09:56:29 +0200 [thread overview]
Message-ID: <20210701075629.GA25768@lst.de> (raw)
In-Reply-To: <20210628151558.2289-4-mwilck@suse.com>
On Mon, Jun 28, 2021 at 05:15:58PM +0200, mwilck@suse.com wrote:
> The qemu "pr-helper" was specifically invented for it. I
> believe that this is the most important real-world scenario for sending
> SG_IO ioctls to device-mapper devices.
pr-helper obviously does not SG_IO on dm-multipath as that simply does
not work.
More importantly - if you want to use persistent reservations use the
kernel ioctls for that. These work on SCSI, NVMe and device mapper
without any extra magic.
Failing over SG_IO does not make sense. It is an interface specically
designed to leave all error handling to the userspace program using it,
and we should not change that for one specific error case. If you
want the kernel to handle errors for you, use the proper interfaces.
In this case this is the persistent reservation ioctls. If they miss
some features that qemu needs we should add those.
--
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dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2021-07-01 8:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 15:15 [dm-devel] [PATCH v5 0/3] scsi/dm: dm_blk_ioctl(): implement failover for SG_IO on dm-multipath mwilck
2021-06-28 15:15 ` [dm-devel] [PATCH v5 1/3] scsi: scsi_ioctl: export __scsi_result_to_blk_status() mwilck
2021-06-28 15:15 ` [dm-devel] [PATCH v5 2/3] scsi: scsi_ioctl: add sg_io_to_blk_status() mwilck
2021-06-28 15:15 ` [dm-devel] [PATCH v5 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO mwilck
2021-07-01 7:56 ` Christoph Hellwig [this message]
2021-07-01 10:35 ` Martin Wilck
2021-07-01 11:34 ` Christoph Hellwig
2021-07-02 14:21 ` Martin Wilck
2021-07-05 13:02 ` Paolo Bonzini
2021-07-05 13:11 ` Hannes Reinecke
2021-07-05 13:48 ` Martin Wilck
2021-07-06 10:13 ` Paolo Bonzini
2021-07-01 11:06 ` Paolo Bonzini
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