nbd: correct disconnect behavior
Paul Clements [Wed, 3 Jul 2013 22:09:04 +0000 (15:09 -0700)]
commit c378f70adbc1bbecd9e6db145019f14b2f688c7c upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/block/nbd.c
include/linux/nbd.h

index 46b35f7..cf1576d 100644 (file)
@@ -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;
        }
 
index 4871170..ae4981e 100644 (file)
@@ -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