From 416b12099e379ec4c19e55a0414a448d140f3dc1 Mon Sep 17 00:00:00 2001

Message-Id: <416b12099e379ec4c19e55a0414a448d140f3dc1@dist-git>

From: Peter Krempa <pkrempa@redhat.com>

Date: Mon, 16 Mar 2020 22:12:16 +0100

Subject: [PATCH] qemu: block: implement helpers for blockdev-reopen

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

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Introduce a set of helpers to call blockdev-reopen in certain scenarios

Libvirt will use the QMP command to turn certain members of the backing

chain read-write for bitmap manipulation and we'll also want to use it

to replace/install the backing chain of a qcow2 format node.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

(cherry picked from commit 96063ce280a398493d7a78a35f674ed25078d849)

https://bugzilla.redhat.com/show_bug.cgi?id=1799013

Message-Id: <f7b3a9cc523a22b9f1678483b6b8bf302ae7e1cc.1584391727.git.pkrempa@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 src/qemu/qemu_block.c | 101 ++++++++++++++++++++++++++++++++++++++++++

 src/qemu/qemu_block.h |   9 ++++

 2 files changed, 110 insertions(+)

diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c

index 141059ae81..b4da323610 100644

--- a/src/qemu/qemu_block.c

+++ b/src/qemu/qemu_block.c

@@ -2986,3 +2986,104 @@ qemuBlockBitmapsHandleBlockcopy(virStorageSourcePtr src,

     return 0;

 }

+

+

+/**

+ * qemuBlockReopenFormat:

+ * @vm: domain object

+ * @src: storage source to reopen

+ * @asyncJob: qemu async job type

+ *

+ * Invokes the 'blockdev-reopen' command on the format layer of @src. This means

+ * that @src must be already properly configured for the desired outcome. The

+ * nodenames of @src are used to identify the specific image in qemu.

+ */

+static int

+qemuBlockReopenFormat(virDomainObjPtr vm,

+                      virStorageSourcePtr src,

+                      qemuDomainAsyncJob asyncJob)

+{

+    qemuDomainObjPrivatePtr priv = vm->privateData;

+    virQEMUDriverPtr driver = priv->driver;

+    g_autoptr(virJSONValue) reopenprops = NULL;

+    int rc;

+

+    /* If we are lacking the object here, qemu might have opened an image with

+     * a node name unknown to us */

+    if (!src->backingStore) {

+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",

+                       _("can't reopen image with unknown presence of backing store"));

+        return -1;

+    }

+

+    if (!(reopenprops = qemuBlockStorageSourceGetBlockdevProps(src, src->backingStore)))

+        return -1;

+

+    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)

+        return -1;

+

+    rc = qemuMonitorBlockdevReopen(priv->mon, &reopenprops);

+

+    if (qemuDomainObjExitMonitor(driver, vm) < 0 || rc < 0)

+        return -1;

+

+    return 0;

+}

+

+

+/**

+ * qemuBlockReopenReadWrite:

+ * @vm: domain object

+ * @src: storage source to reopen

+ * @asyncJob: qemu async job type

+ *

+ * Wrapper that reopens @src read-write. We currently depend on qemu

+ * reopening the storage with 'auto-read-only' enabled for us.

+ * After successful reopen @src's 'readonly' flag is modified. Does nothing

+ * if @src is already read-write.

+ */

+int

+qemuBlockReopenReadWrite(virDomainObjPtr vm,

+                         virStorageSourcePtr src,

+                         qemuDomainAsyncJob asyncJob)

+{

+    if (!src->readonly)

+        return 0;

+

+    src->readonly = false;

+    if (qemuBlockReopenFormat(vm, src, asyncJob) < 0) {

+        src->readonly = true;

+        return -1;

+    }

+

+    return 0;

+}

+

+

+/**

+ * qemuBlockReopenReadOnly:

+ * @vm: domain object

+ * @src: storage source to reopen

+ * @asyncJob: qemu async job type

+ *

+ * Wrapper that reopens @src read-only. We currently depend on qemu

+ * reopening the storage with 'auto-read-only' enabled for us.

+ * After successful reopen @src's 'readonly' flag is modified. Does nothing

+ * if @src is already read-only.

+ */

+int

+qemuBlockReopenReadOnly(virDomainObjPtr vm,

+                         virStorageSourcePtr src,

+                         qemuDomainAsyncJob asyncJob)

+{

+    if (src->readonly)

+        return 0;

+

+    src->readonly = true;

+    if (qemuBlockReopenFormat(vm, src, asyncJob) < 0) {

+        src->readonly = false;

+        return -1;

+    }

+

+    return 0;

+}

diff --git a/src/qemu/qemu_block.h b/src/qemu/qemu_block.h

index 197f5dae97..e012052352 100644

--- a/src/qemu/qemu_block.h

+++ b/src/qemu/qemu_block.h

@@ -231,3 +231,12 @@ qemuBlockBitmapsHandleBlockcopy(virStorageSourcePtr src,

                                 virHashTablePtr blockNamedNodeData,

                                 bool shallow,

                                 virJSONValuePtr *actions);

+

+int

+qemuBlockReopenReadWrite(virDomainObjPtr vm,

+                         virStorageSourcePtr src,

+                         qemuDomainAsyncJob asyncJob);

+int

+qemuBlockReopenReadOnly(virDomainObjPtr vm,

+                        virStorageSourcePtr src,

+                        qemuDomainAsyncJob asyncJob);

-- 

2.25.1