[Qemu-devel] [PATCH v2] RFC: Add blockdev-del QMP command

[Ian Main <imain@redhat.com>]

This is the sister command to blockdev-add.  In Fam's example he uses
the drive_del HMP command to clean up but it would be much nicer to
have a way to do this via QMP.

Signed-off-by: Ian Main <imain@redhat.com>
---

v2:
- s/blockdev-delete/blockdev-del
- Fixed example.

 blockdev.c       | 52 ++++++++++++++++++++++++++++++++++++++--------------
 qapi-schema.json | 11 +++++++++++
 qmp-commands.hx  | 30 ++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 14 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 7372721..96d0da1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1733,21 +1733,9 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
     }
 }
 
-int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
+/* This is called by both do_drive_del() and qmp_blockdev_del */
+static int drive_del_core(BlockDriverState *bs)
 {
-    const char *id = qdict_get_str(qdict, "id");
-    BlockDriverState *bs;
-
-    bs = bdrv_find(id);
-    if (!bs) {
-        qerror_report(QERR_DEVICE_NOT_FOUND, id);
-        return -1;
-    }
-    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, NULL)) {
-        qerror_report(QERR_DEVICE_IN_USE, id);
-        return -1;
-    }
-
     /* quiesce block driver; prevent further io */
     bdrv_drain_all();
     bdrv_flush(bs);
@@ -1771,6 +1759,25 @@ int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
     return 0;
 }
 
+int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
+{
+    const char *id = qdict_get_str(qdict, "id");
+    BlockDriverState *bs;
+
+    bs = bdrv_find(id);
+    if (!bs) {
+        qerror_report(QERR_DEVICE_NOT_FOUND, id);
+        return -1;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, NULL)) {
+        qerror_report(QERR_DEVICE_IN_USE, id);
+        return -1;
+    }
+
+    return drive_del_core(bs);
+}
+
 void qmp_block_resize(bool has_device, const char *device,
                       bool has_node_name, const char *node_name,
                       int64_t size, Error **errp)
@@ -2386,6 +2393,23 @@ fail:
     qmp_output_visitor_cleanup(ov);
 }
 
+void qmp_blockdev_del(const char *device, Error **errp)
+{
+    BlockDriverState *bs;
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_setg(errp, "Block device not found");
+        return;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, NULL)) {
+        return;
+    }
+
+    drive_del_core(bs);
+}
+
 static void do_qmp_query_block_jobs_one(void *opaque, BlockDriverState *bs)
 {
     BlockJobInfoList **prev = opaque;
diff --git a/qapi-schema.json b/qapi-schema.json
index d22651c..01186cd 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4469,3 +4469,14 @@
 # Since: 1.7
 ##
 { 'command': 'blockdev-add', 'data': { 'options': 'BlockdevOptions' } }
+
+##
+# @blockdev-del:
+#
+# Delete a block device.
+#
+# @device: Identifier for the block device to be deleted.
+#
+# Since: 2.0
+##
+{ 'command': 'blockdev-del', 'data': { 'device': 'str' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c3ee46a..f08045d 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3442,6 +3442,36 @@ Example (2):
 EQMP
 
     {
+        .name       = "blockdev-del",
+        .args_type  = "device:s",
+        .mhandler.cmd_new = qmp_marshal_input_blockdev_del,
+    },
+
+SQMP
+blockdev-del
+------------
+
+Remove host block device.  The result is that guest generated IO is no
+longer submitted against the host device underlying the disk.  Once a
+drive has been deleted, the QEMU Block layer returns -EIO which results
+in IO errors in the guest for applications that are reading/writing to
+the device.  These errors are always reported to the guest, regardless
+of the drive's error actions (drive options rerror, werror).
+
+Arguments:
+
+- "device": Identifier of the block device (json-string)
+
+Example (1):
+
+-> { "execute": "blockdev-del",
+                "arguments": { "device": "target0" }
+   }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "query-named-block-nodes",
         .args_type  = "",
         .mhandler.cmd_new = qmp_marshal_input_query_named_block_nodes,
-- 
1.8.3.1