[PATCH 2/4] xen-block: Fix inverted error check in xen_cdrom_realize()

[Mitsuru Kariya <Mitsuru.Kariya@xxxxxxxxxxxxxxx>]

xen_cdrom_realize() checks the return value of blk_attach_dev() with

    if (!rc) {
        error_setg_errno(errp, -rc, "failed to create drive");
        return;
    }

but blk_attach_dev() returns 0 on success and a negative errno on
failure.  The condition is inverted: a successful attach (rc == 0) is
reported as an error and fails realize, while a real failure (rc < 0)
is silently ignored.

Here blk_attach_dev() is called on a BlockBackend just created by
blk_new(), so blk->dev is NULL and its only failure path (-EBUSY)
cannot be taken.  Replace the bogus check with an assertion, matching
the other empty-drive realize paths (scsi-disk, ide, fdc, swim).

Signed-off-by: Mitsuru Kariya <Mitsuru.Kariya@xxxxxxxxxxxxxxx>
---
 hw/block/xen-block.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index 474c12fe4a..abf9df2eee 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -762,10 +762,7 @@ static void xen_cdrom_realize(XenBlockDevice *blockdev, 
Error **errp)
         conf->blk = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
 
         rc = blk_attach_dev(conf->blk, DEVICE(blockdev));
-        if (!rc) {
-            error_setg_errno(errp, -rc, "failed to create drive");
-            return;
-        }
+        assert(rc == 0);
     }
 
     blockdev->info = VDISK_READONLY | VDISK_CDROM;
-- 
2.43.0