block: Attach bs->file only during .bdrv_open()
The way that attaching bs->file worked was a bit unusual in that it was
the only child that would be attached to a node which is not opened yet.
Because of this, the block layer couldn't know yet which permissions the
driver would eventually need.
This patch moves the point where bs->file is attached to the beginning
of the individual .bdrv_open() implementations, so drivers already know
what they are going to do with the child. This is also more consistent
with how driver-specific children work.
For a moment, bdrv_open() gets its own BdrvChild to perform image
probing, but instead of directly assigning this BdrvChild to the BDS, it
becomes a temporary one and the node name is passed as an option to the
drivers, so that they can simply use bdrv_open_child() to create another
reference for their own use.
This duplicated child for (the not opened yet) bs is not the final
state, a follow-up patch will change the image probing code to use a
BlockBackend, which is completely independent of bs.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/tests/qemu-iotests/051.pc.out b/tests/qemu-iotests/051.pc.out
index f8047a2..e206ad6 100644
--- a/tests/qemu-iotests/051.pc.out
+++ b/tests/qemu-iotests/051.pc.out
@@ -323,7 +323,7 @@
QEMU_PROG: -drive driver=nbd: NBD server address missing
Testing: -drive driver=raw
-QEMU_PROG: -drive driver=raw: Can't use 'raw' as a block driver for the protocol level
+QEMU_PROG: -drive driver=raw: A block device must be specified for "file"
Testing: -drive file.driver=file
QEMU_PROG: -drive file.driver=file: The 'file' block driver requires a file name
@@ -332,7 +332,7 @@
QEMU_PROG: -drive file.driver=nbd: NBD server address missing
Testing: -drive file.driver=raw
-QEMU_PROG: -drive file.driver=raw: Can't use 'raw' as a block driver for the protocol level
+QEMU_PROG: -drive file.driver=raw: A block device must be specified for "file"
Testing: -drive foo=bar
QEMU_PROG: -drive foo=bar: Must specify either driver or file
