blockdev: Add blockdev-remove-medium

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -2147,6 +2147,57 @@ void qmp_blockdev_close_tray(const char *device, Error **errp)
     blk_dev_change_media_cb(blk, true);
 }
 
+void qmp_blockdev_remove_medium(const char *device, Error **errp)
+{
+    BlockBackend *blk;
+    BlockDriverState *bs;
+    AioContext *aio_context;
+    bool has_device;
+
+    blk = blk_by_name(device);
+    if (!blk) {
+        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
+                  "Device '%s' not found", device);
+        return;
+    }
+
+    /* For BBs without a device, we can exchange the BDS tree at will */
+    has_device = blk_get_attached_dev(blk);
+
+    if (has_device && !blk_dev_has_removable_media(blk)) {
+        error_setg(errp, "Device '%s' is not removable", device);
+        return;
+    }
+
+    if (has_device && !blk_dev_is_tray_open(blk)) {
+        error_setg(errp, "Tray of device '%s' is not open", device);
+        return;
+    }
+
+    bs = blk_bs(blk);
+    if (!bs) {
+        return;
+    }
+
+    aio_context = bdrv_get_aio_context(bs);
+    aio_context_acquire(aio_context);
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_EJECT, errp)) {
+        goto out;
+    }
+
+    /* This follows the convention established by bdrv_make_anon() */
+    if (bs->device_list.tqe_prev) {
+        QTAILQ_REMOVE(&bdrv_states, bs, device_list);
+        bs->device_list.tqe_prev = NULL;
+    }
+
+    blk_remove_bs(blk);
+
+out:
+    aio_context_release(aio_context);
+}
+
 /* throttling disk I/O limits */
 void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
                                int64_t bps_wr,

qapi/block-core.json

@@ -1924,6 +1924,22 @@
 { 'command': 'blockdev-close-tray',
   'data': { 'device': 'str' } }
 
+##
+# @blockdev-remove-medium:
+#
+# Removes a medium (a block driver state tree) from a block device. That block
+# device's tray must currently be open (unless there is no attached guest
+# device).
+#
+# If the tray is open and there is no medium inserted, this will be a no-op.
+#
+# @device: block device name
+#
+# Since: 2.5
+##
+{ 'command': 'blockdev-remove-medium',
+  'data': { 'device': 'str' } }
+
 
 ##
 # @BlockErrorAction

qmp-commands.hx

@@ -4035,6 +4035,51 @@ Example:
 
 <- { "return": {} }
 
+EQMP
+
+    {
+        .name       = "blockdev-remove-medium",
+        .args_type  = "device:s",
+        .mhandler.cmd_new = qmp_marshal_blockdev_remove_medium,
+    },
+
+SQMP
+blockdev-remove-medium
+----------------------
+
+Removes a medium (a block driver state tree) from a block device. That block
+device's tray must currently be open (unless there is no attached guest device).
+
+If the tray is open and there is no medium inserted, this will be a no-op.
+
+Arguments:
+
+- "device": block device name (json-string)
+
+Example:
+
+-> { "execute": "blockdev-remove-medium",
+     "arguments": { "device": "ide1-cd0" } }
+
+<- { "error": { "class": "GenericError",
+                "desc": "Tray of device 'ide1-cd0' is not open" } }
+
+-> { "execute": "blockdev-open-tray",
+     "arguments": { "device": "ide1-cd0" } }
+
+<- { "timestamp": { "seconds": 1418751627,
+                    "microseconds": 549958 },
+     "event": "DEVICE_TRAY_MOVED",
+     "data": { "device": "ide1-cd0",
+               "tray-open": true } }
+
+<- { "return": {} }
+
+-> { "execute": "blockdev-remove-medium",
+     "arguments": { "device": "ide1-cd0" } }
+
+<- { "return": {} }
+
 EQMP
 
     {