From: Hannes Reinecke <hare@suse.de>
To: Paolo Bonzini <pbonzini@redhat.com>,
Martin Wilck <mwilck@suse.com>, Christoph Hellwig <hch@lst.de>
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,
"Martin K. Petersen" <martin.petersen@oracle.com>,
nkoenig@redhat.com, Bart Van Assche <Bart.VanAssche@sandisk.com>,
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: Mon, 5 Jul 2021 15:11:30 +0200 [thread overview]
Message-ID: <5909eff8-82fb-039e-41d3-1612c22498a9@suse.de> (raw)
In-Reply-To: <e6d76740-e0ed-861a-ef0c-959e738c3ef5@redhat.com>
On 7/5/21 3:02 PM, Paolo Bonzini wrote:
> On 02/07/21 16:21, Martin Wilck wrote:
>>> SG_IO gives you raw access to the SCSI logic unit, and you get to
>>> keep the pieces if anything goes wrong.
>>
>> That's a very fragile user space API, on the fringe of being useless
>> IMO.
>
> Indeed. If SG_IO is for raw access to an ITL nexus, it shouldn't be
> supported at all by mpath devices. If on the other hand SG_IO is for
> raw access to a LUN, there is no reason for it to not support failover.
>
Or we look at IO_URING_OP_URING_CMD, to send raw cdbs via io_uring.
And delegate SG_IO to raw access to an ITL nexus.
Doesn't help with existing issues, but should get a clean way forward.
... I think I've even tendered a topic at LSF for this ...
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
next prev parent reply other threads:[~2021-07-05 13:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 15:15 [PATCH v5 0/3] scsi/dm: dm_blk_ioctl(): implement failover for SG_IO on dm-multipath mwilck
2021-06-28 15:15 ` [PATCH v5 1/3] scsi: scsi_ioctl: export __scsi_result_to_blk_status() mwilck
2021-06-28 15:15 ` [PATCH v5 2/3] scsi: scsi_ioctl: add sg_io_to_blk_status() mwilck
2021-06-28 15:15 ` [PATCH v5 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO mwilck
2021-07-01 7:56 ` Christoph Hellwig
2021-07-01 10:35 ` Martin Wilck
2021-07-01 11:34 ` Christoph Hellwig
2021-07-02 14:21 ` [dm-devel] " Martin Wilck
2021-07-05 13:02 ` Paolo Bonzini
2021-07-05 13:11 ` Hannes Reinecke [this message]
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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