block: Allow BDRV_REQ_FUA through blk_pwrite()

We have several block drivers that understand BDRV_REQ_FUA,
and emulate it in the block layer for the rest by a full flush.
But without a way to actually request BDRV_REQ_FUA during a
pass-through blk_pwrite(), FUA-aware block drivers like NBD are
forced to repeat the emulation logic of a full flush regardless
of whether the backend they are writing to could do it more
efficiently.

This patch just wires up a flags argument; followup patches
will actually make use of it in the NBD driver and in qemu-io.

Signed-off-by: Eric Blake <eblake@redhat.com>
Acked-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/nbd/server.c b/nbd/server.c
index 2184c64..fa862cd 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1115,7 +1115,7 @@ static void nbd_trip(void *opaque)
         TRACE("Writing to device");
 
         ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
-                        req->data, request.len);
+                         req->data, request.len, 0);
         if (ret < 0) {
             LOG("writing to file failed");
             reply.error = -ret;