nbd: correct disconnect behavior

Currently, when a disconnect is requested by the user (via NBD_DISCONNECT
ioctl) the return from NBD_DO_IT is undefined (it is usually one of
several error codes).  This means that nbd-client does not know if a
manual disconnect was performed or whether a network error occurred.
Because of this, nbd-client's persist mode (which tries to reconnect after
error, but not after manual disconnect) does not always work correctly.

This change fixes this by causing NBD_DO_IT to always return 0 if a user
requests a disconnect.  This means that nbd-client can correctly either
persist the connection (if an error occurred) or disconnect (if the user
requested it).

Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Acked-by: Rob Landley <rob@landley.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 7 insertions, 1 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7ed1308c42d3..2dc3b5153f0d 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -623,8 +623,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                 if (!nbd->sock)
                         return -EINVAL;
 
+                nbd->disconnect = 1;
+
                 nbd_send_req(nbd, &sreq);
-                return 0;
+                return 0;
         }
  
         case NBD_CLEAR_SOCK: {
@@ -654,6 +656,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                                 nbd->sock = SOCKET_I(inode);
                                 if (max_part > 0)
                                         bdev->bd_invalidated = 1;
+                                nbd->disconnect = 0; /* we're connected now */
                                 return 0;
                         } else {
                                 fput(file);
@@ -743,6 +746,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                 set_capacity(nbd->disk, 0);
                 if (max_part > 0)
                         ioctl_by_bdev(bdev, BLKRRPART, 0);
+                if (nbd->disconnect) /* user requested, ignore socket errors */
+                        return 0;
                 return nbd->harderror;
         }
 
diff --git a/include/linux/nbd.h b/include/linux/nbd.h
index 4871170a04a0..ae4981ebd18e 100644
--- a/include/linux/nbd.h
+++ b/include/linux/nbd.h
@@ -41,6 +41,7 @@ struct nbd_device {
         u64 bytesize;
         pid_t pid; /* pid of nbd-client, if attached */
         int xmit_timeout;
+        int disconnect; /* a disconnect has been requested by user */
 };
 
 #endif