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, 2 insertions, 1 deletions

diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index c62b6fe96d..6991b2610c 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -102,7 +102,8 @@ BlockAIOCB *blk_aio_write_zeroes(BlockBackend *blk, int64_t sector_num,
                                  int nb_sectors, BdrvRequestFlags flags,
                                  BlockCompletionFunc *cb, void *opaque);
 int blk_pread(BlockBackend *blk, int64_t offset, void *buf, int count);
-int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count);
+int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count,
+               BdrvRequestFlags flags);
 int64_t blk_getlength(BlockBackend *blk);
 void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr);
 int64_t blk_nb_sectors(BlockBackend *blk);