1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index ade146bf65e5..695c68fedd32 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -98,6 +98,7 @@ static const char *nbdcmd_to_ascii(int cmd)
         case  NBD_CMD_READ: return "read";
         case NBD_CMD_WRITE: return "write";
         case  NBD_CMD_DISC: return "disconnect";
+        case NBD_CMD_FLUSH: return "flush";
         case  NBD_CMD_TRIM: return "trim/discard";
         }
         return "invalid";
@@ -244,8 +245,15 @@ static int nbd_send_req(struct nbd_device *nbd, struct request *req)
 
         request.magic = htonl(NBD_REQUEST_MAGIC);
         request.type = htonl(nbd_cmd(req));
-        request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
-        request.len = htonl(size);
+
+        if (nbd_cmd(req) == NBD_CMD_FLUSH) {
+                /* Other values are reserved for FLUSH requests.  */
+                request.from = 0;
+                request.len = 0;
+        } else {
+                request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
+                request.len = htonl(size);
+        }
         memcpy(request.handle, &req, sizeof(req));
 
         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%uB)\n",
@@ -482,6 +490,11 @@ static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
                 }
         }
 
+        if (req->cmd_flags & REQ_FLUSH) {
+                BUG_ON(unlikely(blk_rq_sectors(req)));
+                nbd_cmd(req) = NBD_CMD_FLUSH;
+        }
+
         req->errors = 0;
 
         mutex_lock(&nbd->tx_lock);
@@ -684,6 +697,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                 if (nbd->flags & NBD_FLAG_SEND_TRIM)
                         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
                                 nbd->disk->queue);
+                if (nbd->flags & NBD_FLAG_SEND_FLUSH)
+                        blk_queue_flush(nbd->disk->queue, REQ_FLUSH);
+                else
+                        blk_queue_flush(nbd->disk->queue, 0);
 
                 thread = kthread_create(nbd_thread, nbd, nbd->disk->disk_name);
                 if (IS_ERR(thread)) {
@@ -705,6 +722,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                 queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
                 if (file)
                         fput(file);
+                nbd->flags = 0;
                 nbd->bytesize = 0;
                 bdev->bd_inode->i_size = 0;
                 set_capacity(nbd->disk, 0);