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Re: [Qemu-devel] [PATCH 2/3] scsi/virtio-scsi: Cleanup of I/Os that neve


From: Eric Farman
Subject: Re: [Qemu-devel] [PATCH 2/3] scsi/virtio-scsi: Cleanup of I/Os that never started
Date: Tue, 14 Jan 2014 11:08:00 -0500
User-agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

On 01/14/2014 09:49 AM, Paolo Bonzini wrote:
Il 14/01/2014 15:24, Eric Farman ha scritto:
There is still a small window that occurs when a cancel I/O affects
an asynchronous I/O operation that hasn't started.  In other words,
when the residual data length equals the expected data length.

Today, the routine virtio_scsi_command_complete fails because the
VirtIOSCSIReq pointer (from the hba_private field in SCSIRequest)
was cleared earlier when virtio_scsi_complete_req was called by
the virtio_scsi_request_cancelled routine.  As a result, the
virtio_scsi_command_complete routine needs to simply return when
it is processing a SCSIRequest block that was marked canceled.

Signed-off-by: Eric Farman <address@hidden>
---
  hw/scsi/virtio-scsi.c |    4 ++++
  1 file changed, 4 insertions(+)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index a8fde04..49a9576 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -306,6 +306,10 @@ static void virtio_scsi_command_complete(SCSIRequest *r, 
uint32_t status,
      VirtIOSCSIReq *req = r->hba_private;
      uint32_t sense_len;
+ if (r->io_canceled) {
+        return;
+    }
+
      req->resp.cmd->response = VIRTIO_SCSI_S_OK;
      req->resp.cmd->status = status;
      if (req->resp.cmd->status == GOOD) {

Reviewed-by: Paolo Bonzini <address@hidden>

Can you please look more closely into whether patch 1 is really
necessary, include the small fix I posted into that review, and post v2
of the series?

Heh, that's fantastic. I pulled patch 1 out, ran the tests that hit into these problems, didn't see anything. Pulled out patch 2, reran the tests, hit them almost immediately. Did this a few times, with the same results. So I'll fix up another series, and post shortly.

Thanks for the feedback and the review!

- Eric

Thanks!

Paolo





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