tree 30a130141b7c4b69ff20d134734acd40f1ee0960
parent 3ca4f5ca73057a617f9444a91022d7127041970a
author Christoph Hellwig <hch@lst.de> 1253210262 +0200
committer Rusty Russell <rusty@rustcorp.com.au> 1253710596 +0930

virtio_blk: add support for cache flush

Recent qemu has added a VIRTIO_BLK_F_FLUSH flag to advertise that the
virtual disk has a volatile write cache that needs to be flushed.  In case
we see this feature implement tell the Linux block layer about the fact
and use the new VIRTIO_BLK_T_FLUSH to flush the cache when required.  This
allows for an correct and simple implementation of write barriers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>