nbd/client: refactor nbd_receive_reply

Refactor nbd_receive_reply to return 1 on success, 0 on eof, when no
data was read and <0 for other cases, because returned size of read
data is not actually used.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170804151440.320927-4-vsementsov@virtuozzo.com>
[eblake: tweak function comments]
Signed-off-by: Eric Blake <eblake@redhat.com>

2 files changed, 10 insertions, 4 deletions

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 9c3d0a5868..f7450608b4 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -164,7 +164,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
 int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
              Error **errp);
 ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request);
-ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp);
+int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp);
 int nbd_client(int fd);
 int nbd_disconnect(int fd);
 
diff --git a/nbd/client.c b/nbd/client.c
index 4556056daa..f8c213bc96 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -914,11 +914,16 @@ ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request)
     return nbd_write(ioc, buf, sizeof(buf), NULL);
 }
 
-ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
+/* nbd_receive_reply
+ * Returns 1 on success
+ *         0 on eof, when no data was read (errp is not set)
+ *         negative errno on failure (errp is set)
+ */
+int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
 {
     uint8_t buf[NBD_REPLY_SIZE];
     uint32_t magic;
-    ssize_t ret;
+    int ret;
 
     ret = nbd_read_eof(ioc, buf, sizeof(buf), errp);
     if (ret <= 0) {
@@ -948,6 +953,7 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
         error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
         return -EINVAL;
     }
-    return sizeof(buf);
+
+    return 1;
 }