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
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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