The server can use it to issue a flush automatically after a
write. The client can also use it to mimic a write-through
cache.
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
block/nbd.c | 8 ++++++++
nbd.c | 13 +++++++++++--
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/block/nbd.c b/block/nbd.c
index b6b2f2d..23f83d4 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -216,6 +216,10 @@ static int nbd_write(BlockDriverState *bs, int64_t
sector_num,
struct nbd_reply reply;
request.type = NBD_CMD_WRITE;
+ if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) {
+ request.type |= NBD_CMD_FLAG_FUA;
+ }
+
request.handle = (uint64_t)(intptr_t)bs;
request.from = sector_num * 512;;
request.len = nb_sectors * 512;
@@ -249,6 +253,10 @@ static int nbd_flush(BlockDriverState *bs)
}
request.type = NBD_CMD_FLUSH;
+ if (s->nbdflags & NBD_FLAG_SEND_FUA) {
+ request.type |= NBD_CMD_FLAG_FUA;
+ }
+
request.handle = (uint64_t)(intptr_t)bs;
request.from = 0;
request.len = 0;
diff --git a/nbd.c b/nbd.c
index f06090b..42ee2b5 100644
--- a/nbd.c
+++ b/nbd.c
@@ -195,7 +195,8 @@ int nbd_negotiate(int csock, off_t size, uint32_t flags)
cpu_to_be64w((uint64_t*)(buf + 8), 0x00420281861253LL);
cpu_to_be64w((uint64_t*)(buf + 16), size);
cpu_to_be32w((uint32_t*)(buf + 24),
- flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH);
+ flags | NBD_FLAG_HAS_FLAGS |
+ NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
memset(buf + 28, 0, 124);
if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
@@ -616,7 +617,7 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size,
uint64_t dev_offset,
reply.handle = request.handle;
reply.error = 0;
- switch (request.type) {
+ switch (request.type & NBD_CMD_MASK_COMMAND) {
case NBD_CMD_READ:
TRACE("Request type is READ");
@@ -678,6 +679,14 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size,
uint64_t dev_offset,
}
*offset += request.len;
+
+ if (request.type & NBD_CMD_FLAG_FUA) {
+ ret = bdrv_flush(bs);
+ if (ret < 0) {
+ LOG("flush failed");
+ reply.error = -ret;
+ }
+ }
}
if (nbd_send_reply(csock, &reply) == -1)
--
1.7.6
