blockdev: Don't disable COR automatically with blockdev-add

If a read-only device is configured with copy-on-read=on, the old code
only prints a warning and automatically disables copy on read. Make it
a real error for blockdev-add.

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

2 files changed, 34 insertions, 6 deletions

diff --git a/block.c b/block.c
index 84c0eac671..fd05a8008a 100644
--- a/block.c
+++ b/block.c
@@ -778,8 +778,13 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     }
 
     assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */
-    if (!bs->read_only && (flags & BDRV_O_COPY_ON_READ)) {
-        bdrv_enable_copy_on_read(bs);
+    if (flags & BDRV_O_COPY_ON_READ) {
+        if (!bs->read_only) {
+            bdrv_enable_copy_on_read(bs);
+        } else {
+            error_setg(errp, "Can't use copy-on-read on read-only device");
+            return -EINVAL;
+        }
     }
 
     if (filename != NULL) {
diff --git a/blockdev.c b/blockdev.c
index e1ad319281..1f14514bea 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -510,10 +510,6 @@ static DriveInfo *blockdev_init(QDict *bs_opts,
 
     bdrv_flags |= ro ? 0 : BDRV_O_RDWR;
 
-    if (ro && copy_on_read) {
-        error_report("warning: disabling copy_on_read on read-only drive");
-    }
-
     QINCREF(bs_opts);
     ret = bdrv_open(dinfo->bdrv, file, bs_opts, bdrv_flags, drv, &error);
 
@@ -601,6 +597,18 @@ QemuOptsList qemu_legacy_drive_opts = {
             .type = QEMU_OPT_STRING,
             .help = "pci address (virtio only)",
         },
+
+        /* Options that are passed on, but have special semantics with -drive */
+        {
+            .name = "read-only",
+            .type = QEMU_OPT_BOOL,
+            .help = "open drive file as read-only",
+        },{
+            .name = "copy-on-read",
+            .type = QEMU_OPT_BOOL,
+            .help = "copy read data from backing file into image file",
+        },
+
         { /* end of list */ }
     },
 };
@@ -616,6 +624,7 @@ DriveInfo *drive_init(QemuOpts *all_opts, BlockInterfaceType block_default_type)
     int cyls, heads, secs, translation;
     int max_devs, bus_id, unit_id, index;
     const char *devaddr;
+    bool read_only, copy_on_read;
     Error *local_err = NULL;
 
     /* Change legacy command line options into QMP ones */
@@ -698,6 +707,20 @@ DriveInfo *drive_init(QemuOpts *all_opts, BlockInterfaceType block_default_type)
         }
     }
 
+    /* copy-on-read is disabled with a warning for read-only devices */
+    read_only = qemu_opt_get_bool(legacy_opts, "read-only", false);
+    copy_on_read = qemu_opt_get_bool(legacy_opts, "copy-on-read", false);
+
+    if (read_only && copy_on_read) {
+        error_report("warning: disabling copy-on-read on read-only drive");
+        copy_on_read = false;
+    }
+
+    qdict_put(bs_opts, "read-only",
+              qstring_from_str(read_only ? "on" : "off"));
+    qdict_put(bs_opts, "copy-on-read",
+              qstring_from_str(copy_on_read ? "on" :"off"));
+
     /* Controller type */
     value = qemu_opt_get(legacy_opts, "if");
     if (value) {