[PATCH] device-mapper statistics: basic

Record basic I/O statistics for mapped devices.
Signed-off-by: Kevin Corry <kevcorry@us.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/dm.c

@@ -573,10 +573,14 @@ static void __split_bio(struct mapped_device *md, struct bio *bio)
 static int dm_request(request_queue_t *q, struct bio *bio)
 {
 	int r;
+	int rw = bio_data_dir(bio);
 	struct mapped_device *md = q->queuedata;
 
 	down_read(&md->io_lock);
 
+	disk_stat_inc(dm_disk(md), ios[rw]);
+	disk_stat_add(dm_disk(md), sectors[rw], bio_sectors(bio));
+
 	/*
 	 * If we're suspended we have to queue
 	 * this io for later.