linux-kernel - Re: [PATCH 1/1] scsi: storvsc: Fix handling of srb

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Date:   Fri, 11 Nov 2022 23:45:42 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     kys@...rosoft.com, martin.petersen@...cle.com,
        longli@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
        jejb@...ux.ibm.com, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [PATCH 1/1] scsi: storvsc: Fix handling of srb_status and
 capacity change events

On Wed, Nov 09, 2022 at 10:48:42AM -0800, Michael Kelley wrote:
> Current handling of the srb_status is incorrect. Commit 52e1b3b3daa9
> ("scsi: storvsc: Correctly handle multiple flags in srb_status")
> is based on srb_status being a set of flags, when in fact only the
> 2 high order bits are flags and the remaining 6 bits are an integer
> status. Because the integer values of interest mostly look like flags,
> the code actually works when treated that way.
> 
> But in the interest of correctness going forward, fix this by treating
> the low 6 bits of srb_status as an integer status code. Add handling
> for SRB_STATUS_INVALID_REQUEST, which was the original intent of commit
> 52e1b3b3daa9. Furthermore, treat the ERROR, ABORTED, and INVALID_REQUEST
> srb status codes as essentially equivalent for the cases we care about.
> There's no harm in doing so, and it isn't always clear which status code
> current or older versions of Hyper-V report for particular conditions.
> 
> Treating the srb status codes as equivalent has the additional benefit
> of ensuring that capacity change events result in an immediate rescan
> so that the new size is known to Linux. Existing code checks SCSI
> sense data for capacity change events when the srb status is ABORTED.
> But capacity change events are also being observed when Hyper-V reports
> the srb status as ERROR. Without the immediate rescan, the new size
> isn't known until something else causes a rescan (such as running
> fdisk to expand a partition), and in the meantime, tools such as "lsblk"
> continue to report the old size.
> 
> Fixes: 52e1b3b3daa9 ("scsi: storvsc: Correctly handle multiple flags in srb_status")
> Reported-by: Juan Tian <juantian@...rosoft.com>
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>

Applied to hyperv-fixes. Thanks.