virtio-blk: use virtqueue_add_sgs on bio path
virtio-blk: use virtqueue_add_sgs on bio path

(This is a respin of Paolo Bonzini's patch, but it calls
virtqueue_add_sgs() instead of his multi-part API).

Move the creation of the request header and response footer to
__virtblk_add_req.  vbr->sg only contains the data scatterlist,
the header/footer are added separately using virtqueue_add_sgs().

With this change, virtio-blk (with use_bio) is not relying anymore on
the virtio functions ignoring the end markers in a scatterlist.
The next patch will do the same for the other path.

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>
Signed-off-by: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>
Reviewed-by: Asias He <7487d0432e24c09ba3f2ff7de44b9eb030d5ae18@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas