Re: virtio-scsi issues duplicate tags when async_abort is enabled

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On 6/13/14, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
...
> OK, I've no idea what's in distro kernels, so you're looking for this
> fix:
>
> commit d555a2abf3481f81303d835046a5ec2c4fb3ca8e
> Author: James Bottomley <JBottomley@xxxxxxxxxxxxx>
> Date:   Fri Mar 28 10:50:17 2014 -0700
>
>     [SCSI] Fix spurious request sense in error handling
>
> It went into v3.15-rc3.  It looks like it wasn't backported to stable.

Backporting this fix to 3.14 appears to resolve this problem. Thank you!

0) I don't understand how a command would be re-issued while its
original is inflight without this patch. If we send down a spurious
REQUESE SENSE and get NO SENSE, scsi_decide_disposition() in
scsi_eh_get_sense() will return FAILED and not resubmit the command.
Do you know the trace that results in the duplicate command being sent
down?

1) virtio-scsi uses the address of the scsi_cmnd as a tag; if
scsi_eh_get_sense() is invoked for a timed-out command before the
command returned, the REQUEST SENSE task from scsi_send_eh_cmnd() will
have the same tag as the unreturned prior task. Scary.

2) We would like to see this patch sent to the stable kernel tree; do
you plan to send it out to stable@? Are there any further tests you
plan to run on that particular fix before sending it that way?

Thanks,
-- vs;
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