From bcfe0f8f7ca6c670783cfaa98f45b6985fcbcc39 Mon Sep 17 00:00:00 2001 Message-Id: From: Fam Zheng Date: Wed, 25 Nov 2015 03:49:11 -0600 Subject: [CHANGE 1/5] virtio-blk: Fix double completion for werror=stop To: rhvirt-patches@redhat.com, jen@redhat.com RH-Author: Fam Zheng Message-id: <1448423352-12857-2-git-send-email-famz@redhat.com> Patchwork-id: 68458 O-Subject: [RHEL-7.2.z qemu-kvm-rhev v2 PATCH 1/2] virtio-blk: Fix double completion for werror=stop Bugzilla: 1277922 1283987 RH-Acked-by: Kevin Wolf RH-Acked-by: Laurent Vivier RH-Acked-by: Paolo Bonzini When a request R is absorbed by request M, it is appended to the "mr_next" queue led by M, and is completed together with the completion of M, in virtio_blk_rw_complete. During DMA restart in virtio_blk_dma_restart_bh, requests in s->rq are parsed and submitted again, possibly with a stale req->mr_next. It could be a problem if the request merging in virtio_blk_handle_request hasn't refreshed every mr_next pointer, in which case, virtio_blk_rw_complete could walk through unexpected requests following the stale pointers. Fix this by unsetting the pointer in virtio_blk_rw_complete. It is safe because this req is either completed and freed right away, or it will be restarted and parsed from scratch out of the vq later. Signed-off-by: Fam Zheng Signed-off-by: Stefan Hajnoczi (cherry picked from commit 10f5a72f70862d299ddbdf226d6dc71fa4ae34dd) Signed-off-by: Fam Zheng Signed-off-by: Jeff E. Nelson --- hw/block/virtio-blk.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 3af6567..5d96f20 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -112,6 +112,10 @@ static void virtio_blk_rw_complete(void *opaque, int ret) * happen on the other side of the migration). */ if (virtio_blk_handle_rw_error(req, -ret, is_read)) { + /* Break the link in case the next request is added to the + * restart queue and is going to be parsed from the ring again. + */ + req->mr_next = NULL; continue; } } -- 2.5.0