block: Add blk_new_open()
blk_new_with_bs() creates a BlockBackend with an empty BlockDriverState attached to it. Empty BDSs are not nice, therefore add an alternative function which combines blk_new_with_bs() with bdrv_open(). Note: In contrast to bdrv_open() which takes a BlockDriver parameter, blk_new_open() does not take such a parameter. This is because bdrv_open() opens a BlockDriverState, therefore it is natural to be able to set the BlockDriver for that BDS. The fact that bdrv_open() can open more than a single BDS is merely some form of a byproduct. blk_new_open() on the other hand is intended to be used to create a whole tree of BlockDriverStates. Therefore, setting a single BlockDriver does not make much sense. Instead, the drivers to be used for each of the nodes must be configured through the "options" QDict; including the driver of the root BDS. Signed-off-by: NMax Reitz <mreitz@redhat.com> Reviewed-by: NEric Blake <eblake@redhat.com> Reviewed-by: NKevin Wolf <kwolf@redhat.com> Message-id: 1423162705-32065-3-git-send-email-mreitz@redhat.com Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
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