block/null: Remove 'filename' option

This option was only added to allow 'null-co://' and 'null-aio://' as
filenames, its value never served any actual purpose and was ignored.
Nevertheless it was accepted as '-drive driver=null,filename=foo'.

The correct way to enable the protocol prefixes (and that without adding
a useless -drive option) is implementing .bdrv_parse_filename. This is
what this patch does.

Technically, this is an incompatible change, but the null block driver
is only used for benchmarking, testing and debugging, and an option
without effect isn't likely to be used by anyone anyway, so no bad
effects are to be expected.
Reported-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

block/null.c

@@ -29,11 +29,6 @@ static QemuOptsList runtime_opts = {
     .name = "null",
     .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
     .desc = {
-        {
-            .name = "filename",
-            .type = QEMU_OPT_STRING,
-            .help = "",
-        },
         {
             .name = BLOCK_OPT_SIZE,
             .type = QEMU_OPT_SIZE,
@@ -54,6 +49,30 @@ static QemuOptsList runtime_opts = {
     },
 };
 
+static void null_co_parse_filename(const char *filename, QDict *options,
+                                   Error **errp)
+{
+    /* This functions only exists so that a null-co:// filename is accepted
+     * with the null-co driver. */
+    if (strcmp(filename, "null-co://")) {
+        error_setg(errp, "The only allowed filename for this driver is "
+                         "'null-co://'");
+        return;
+    }
+}
+
+static void null_aio_parse_filename(const char *filename, QDict *options,
+                                    Error **errp)
+{
+    /* This functions only exists so that a null-aio:// filename is accepted
+     * with the null-aio driver. */
+    if (strcmp(filename, "null-aio://")) {
+        error_setg(errp, "The only allowed filename for this driver is "
+                         "'null-aio://'");
+        return;
+    }
+}
+
 static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
                           Error **errp)
 {
@@ -242,6 +261,7 @@ static BlockDriver bdrv_null_co = {
     .instance_size          = sizeof(BDRVNullState),
 
     .bdrv_file_open         = null_file_open,
+    .bdrv_parse_filename    = null_co_parse_filename,
     .bdrv_close             = null_close,
     .bdrv_getlength         = null_getlength,
 
@@ -261,6 +281,7 @@ static BlockDriver bdrv_null_aio = {
     .instance_size          = sizeof(BDRVNullState),
 
     .bdrv_file_open         = null_file_open,
+    .bdrv_parse_filename    = null_aio_parse_filename,
     .bdrv_close             = null_close,
     .bdrv_getlength         = null_getlength,
 

tests/qemu-iotests/136

@@ -75,7 +75,7 @@ sector = "%d"
         drive_args.append("stats-account-failed=%s" %
                           (self.account_failed and "on" or "off"))
         self.create_blkdebug_file()
-        self.vm = iotests.VM().add_drive('blkdebug:%s:%s ' %
+        self.vm = iotests.VM().add_drive('blkdebug:%s:%s' %
                                          (blkdebug_file, self.test_img),
                                          ','.join(drive_args))
         self.vm.launch()