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    SubjectRe: [REGRESSION][Stable][v3.12.y][v4.4.y][v4.9.y][v4.10.y][v4.11-rc1] scsi: storvsc: properly set residual data length on errors
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    On 03/27/2017 06:14 PM, Stephen Hemminger wrote:
    > Are you sure the real problem is not the one fixed by this commit?
    >
    > commit f1c635b439a5c01776fe3a25b1e2dc546ea82e6f
    > Author: Stephen Hemminger <stephen@networkplumber.org>
    > Date: Tue Mar 7 09:15:53 2017 -0800
    >
    > scsi: storvsc: Workaround for virtual DVD SCSI version
    >
    > Hyper-V host emulation of SCSI for virtual DVD device reports SCSI
    > version 0 (UNKNOWN) but is still capable of supporting REPORTLUN.
    >
    > Without this patch, a GEN2 Linux guest on Hyper-V will not boot 4.11
    > successfully with virtual DVD ROM device. What happens is that the SCSI
    > scan process falls back to doing sequential probing by INQUIRY. But the
    > storvsc driver has a previous workaround that masks/blocks all errors
    > reports from INQUIRY (or MODE_SENSE) commands. This workaround causes
    > the scan to then populate a full set of bogus LUN's on the target and
    > then sends kernel spinning off into a death spiral doing block reads on
    > the non-existent LUNs.
    >
    > By setting the correct blacklist flags, the target with the DVD device
    > is scanned with REPORTLUN and that works correctly.
    >
    > Patch needs to go in current 4.11, it is safe but not necessary in older
    > kernels.
    >
    > Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
    > Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
    > Reviewed-by: Christoph Hellwig <hch@lst.de>
    > Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    >
    > -----Original Message-----
    > From: Joseph Salisbury [mailto:joseph.salisbury@canonical.com]
    > Sent: Monday, March 27, 2017 1:22 PM
    > To: Long Li <longli@microsoft.com>
    > Cc: KY Srinivasan <kys@microsoft.com>; Martin K. Petersen <martin.petersen@oracle.com>; Haiyang Zhang <haiyangz@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com>; jejb@linux.vnet.ibm.com; devel@linuxdriverproject.org; linux-scsi <linux-scsi@vger.kernel.org>; LKML <linux-kernel@vger.kernel.org>; stable@vger.kernel.org; Greg KH <gregkh@linuxfoundation.org>
    > Subject: [REGRESSION][Stable][v3.12.y][v4.4.y][v4.9.y][v4.10.y][v4.11-rc1] scsi: storvsc: properly set residual data length on errors
    >
    > Hi Long Li,
    >
    > A kernel bug report was opened against Ubuntu [0]. After a kernel
    > bisect, it was found that reverting the following commit resolved this bug:
    >
    > commit 40630f462824ee24bc00d692865c86c3828094e0
    > Author: Long Li <longli@microsoft.com>
    > Date: Wed Dec 14 18:46:03 2016 -0800
    >
    > scsi: storvsc: properly set residual data length on errors
    >
    >
    > The regression was introduced in mainline as of v4.11-rc1. It was also
    > cc'd to stable and has landed in v3.12.y, v4.4.y, v4.9.y and v4.10.y.
    >
    >
    > This regression seems pretty severe since it's preventing virtual
    > machines from booting. It's affecting a couple of users so far. I was
    > hoping to get your feedback, since you are the patch author. Do you
    > think gathering any additional data will help diagnose this issue, or
    > would it be best to submit a revert request?
    >
    >
    > Thanks,
    >
    > Joe
    >
    >
    > [0] http://pad.lv/1674635
    >
    >
    Thanks for the pointer, Stephen. I'll have this patch tested and
    respond with the results.


    Joe

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