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Blame SOURCES/0017-virtio-scsi-Reject-scsi-cd-if-data-plane-enabled-RHE.patch

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From 41fe05330d095f69f12973b0540466439e030047 Mon Sep 17 00:00:00 2001
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From: Fam Zheng <famz@redhat.com>
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Date: Wed, 14 Jun 2017 15:37:01 +0200
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Subject: virtio-scsi: Reject scsi-cd if data plane enabled [RHEL only]
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RH-Author: Fam Zheng <famz@redhat.com>
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Message-id: <20170614153701.14757-1-famz@redhat.com>
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Patchwork-id: 75613
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O-Subject: [RHV-7.4 qemu-kvm-rhev PATCH v3] virtio-scsi: Reject scsi-cd if data plane enabled [RHEL only]
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Bugzilla: 1378816
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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We need a fix for RHEL 7.4 and 7.3.z, but unfortunately upstream isn't
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ready. If it were, the changes will be too invasive. To have an idea:
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https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg05400.html
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is an incomplete attempt to fix part of the issue, and the remaining
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work unfortunately involve even more complex changes.
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As a band-aid, this partially reverts the effect of ef8875b
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(virtio-scsi: Remove op blocker for dataplane, since v2.7). We cannot
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simply revert that commit as a whole because we already shipped it in
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qemu-kvm-rhev 7.3, since when, block jobs has been possible.  We should
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only block what has been broken.  Also, faithfully reverting the above
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commit means adding back the removed op blocker, but that is not enough,
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because it still crashes when inserting media into an initially empty
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scsi-cd.
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All in all, scsi-cd on virtio-scsi-dataplane has basically been unusable
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unless the scsi-cd never enters an empty state, so, disable it
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altogether.  Otherwise it would be much more difficult to avoid
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crashing.
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/scsi/virtio-scsi.c | 9 +++++++++
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 1 file changed, 9 insertions(+)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index 51fd09522a..a35257c35a 100644
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--- a/hw/scsi/virtio-scsi.c
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+++ b/hw/scsi/virtio-scsi.c
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@@ -896,6 +896,15 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
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     AioContext *old_context;
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     int ret;
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+    /* XXX: Remove this check once block backend is capable of handling
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+     * AioContext change upon eject/insert.
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+     * s->ctx is NULL if ioeventfd is off, s->ctx is qemu_get_aio_context() if
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+     * data plane is not used, both cases are safe for scsi-cd. */
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+    if (s->ctx && s->ctx != qemu_get_aio_context() &&
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+        object_dynamic_cast(OBJECT(dev), "scsi-cd")) {
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+        error_setg(errp, "scsi-cd is not supported by data plane");
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+        return;
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+    }
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     if (s->ctx && !s->dataplane_fenced) {
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         if (blk_op_is_blocked(sd->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
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             return;
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-- 
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2.27.0
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