[PATCH] fix disk IO stats for 512-byte IOs

If you're peforming 512-byte sized IOs.  With, say,

	dd of=/dev/raw/raw1 bs=512

then the `pgpgin' and `pgpgout' accounting just sits on zero.

This is because it counts in kbytes, and 512/1024 is zero.

So change it to count sectors, and divide that by two when we report it
to userspace.

drivers/block/ll_rw_blk.c

@@ -1878,7 +1878,7 @@ void generic_make_request(struct bio *bio)
  */
 int submit_bio(int rw, struct bio *bio)
 {
-	int count = bio_sectors(bio) >> 1;
+	int count = bio_sectors(bio);
 
 	BUG_ON(!bio->bi_end_io);
 	BIO_BUG_ON(!bio->bi_size);

mm/page_alloc.c

@@ -1147,6 +1147,8 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 	if (!ps)
 		return ERR_PTR(-ENOMEM);
 	get_full_page_state(ps);
+	ps->pgpgin /= 2;		/* sectors -> kbytes */
+	ps->pgpgout /= 2;
 	return (unsigned long *)ps + *pos;
 }