[Qemu-devel] [PATCH v3 10/15] nbd: add support for NBD_CMD_FLUSH

[Paolo Bonzini <pbonzini@redhat.com>]

Note for the brace police: the style in this commit and the following
is consistent with the rest of the file.  It is then fixed together with
the introduction of coroutines.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/nbd.c |   31 +++++++++++++++++++++++++++++++
 nbd.c       |   15 ++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 76f04d8..b6b2f2d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -238,6 +238,36 @@ static int nbd_write(BlockDriverState *bs, int64_t sector_num,
     return 0;
 }
 
+static int nbd_flush(BlockDriverState *bs)
+{
+    BDRVNBDState *s = bs->opaque;
+    struct nbd_request request;
+    struct nbd_reply reply;
+
+    if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) {
+        return 0;
+    }
+
+    request.type = NBD_CMD_FLUSH;
+    request.handle = (uint64_t)(intptr_t)bs;
+    request.from = 0;
+    request.len = 0;
+
+    if (nbd_send_request(s->sock, &request) == -1)
+        return -errno;
+
+    if (nbd_receive_reply(s->sock, &reply) == -1)
+        return -errno;
+
+    if (reply.error != 0)
+        return -reply.error;
+
+    if (reply.handle != request.handle)
+        return -EIO;
+
+    return 0;
+}
+
 static void nbd_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
@@ -261,6 +291,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_read		= nbd_read,
     .bdrv_write		= nbd_write,
     .bdrv_close		= nbd_close,
+    .bdrv_flush		= nbd_flush,
     .bdrv_getlength	= nbd_getlength,
     .protocol_name	= "nbd",
 };
diff --git a/nbd.c b/nbd.c
index 5df9745..f06090b 100644
--- a/nbd.c
+++ b/nbd.c
@@ -194,7 +194,8 @@ int nbd_negotiate(int csock, off_t size, uint32_t flags)
     memcpy(buf, "NBDMAGIC", 8);
     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);
+    cpu_to_be32w((uint32_t*)(buf + 24),
+                 flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH);
     memset(buf + 28, 0, 124);
 
     if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
@@ -686,6 +687,18 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
         TRACE("Request type is DISCONNECT");
         errno = 0;
         return 1;
+    case NBD_CMD_FLUSH:
+        TRACE("Request type is FLUSH");
+
+        ret = bdrv_flush(bs);
+        if (ret < 0) {
+            LOG("flush failed");
+            reply.error = -ret;
+        }
+
+        if (nbd_send_reply(csock, &reply) == -1)
+            return -1;
+        break;
     default:
         LOG("invalid request type (%u) received", request.type);
         errno = EINVAL;
-- 
1.7.6