[PATCH] nbd: show nbd client pid in sysfs

Allow nbd to expose the nbd-client daemon's PID in /sys/block/nbd<x>/pid.

This is helpful for tracking connection status of a device and for
determining which nbd devices are currently in use.

Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/nbd.h

@@ -64,6 +64,7 @@ struct nbd_device {
 	struct gendisk *disk;
 	int blksize;
 	u64 bytesize;
+	pid_t pid; /* pid of nbd-client, if attached */
 };
 
 #endif