linux-kernel - Re: [PATCH v3] scsi: storvsc: Correct reporting of Hyper-V I/O size limits

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Date:   Thu, 16 Jun 2022 22:20:19 -0400
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     haiyangz@...rosoft.com,
        Saurabh Sengar <ssengar@...ux.microsoft.com>,
        wei.liu@...nel.org, kys@...rosoft.com,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-scsi@...r.kernel.org, mikelley@...rosoft.com,
        decui@...rosoft.com, sthemmin@...rosoft.com, jejb@...ux.ibm.com,
        ssengar@...rosoft.com
Cc:     "Martin K . Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH v3] scsi: storvsc: Correct reporting of Hyper-V I/O size limits

On Tue, 14 Jun 2022 00:05:55 -0700, Saurabh Sengar wrote:

> Current code is based on the idea that the max number of SGL entries
> also determines the max size of an I/O request.  While this idea was
> true in older versions of the storvsc driver when SGL entry length
> was limited to 4 Kbytes, commit 3d9c3dcc58e9 ("scsi: storvsc: Enable
> scatterlist entry lengths > 4Kbytes") removed that limitation. It's
> now theoretically possible for the block layer to send requests that
> exceed the maximum size supported by Hyper-V. This problem doesn't
> currently happen in practice because the block layer defaults to a
> 512 Kbyte maximum, while Hyper-V in Azure supports 2 Mbyte I/O sizes.
> But some future configuration of Hyper-V could have a smaller max I/O
> size, and the block layer could exceed that max.
> 
> [...]

Applied to 5.19/scsi-fixes, thanks!

[1/1] scsi: storvsc: Correct reporting of Hyper-V I/O size limits
      https://git.kernel.org/mkp/scsi/c/1d3e0980782f

-- 
Martin K. Petersen	Oracle Linux Engineering