[PATCH] pktcdvd: bio write congestion using congestion_wait()

This adds a bio write queue congestion control to the pktcdvd driver with
fixed on/off marks.  It prevents that the driver consumes a unlimited
amount of write requests.

[akpm@osdl.org: sync with congestion_wait() renaming]
Signed-off-by: Thomas Maier <balagi@justmail.de>
Cc: Peter Osterlund <petero2@telia.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/pktcdvd.h

@@ -112,6 +112,12 @@ struct pkt_ctrl_command {
 #include <linux/completion.h>
 #include <linux/cdrom.h>
 
+
+/* default bio write queue congestion marks */
+#define PKT_WRITE_CONGESTION_ON    10000
+#define PKT_WRITE_CONGESTION_OFF   9000
+
+
 struct packet_settings
 {
 	__u32			size;		/* packet size in (512 byte) sectors */
@@ -271,6 +277,9 @@ struct pktcdvd_device
 
 	struct packet_iosched   iosched;
 	struct gendisk		*disk;
+
+	int			write_congestion_off;
+	int			write_congestion_on;
 };
 
 #endif /* __KERNEL__ */