[PATCH] ll_rw_blk: allow more flexibility for read_ahead_kb store

It can make sense to set read-ahead larger than a single request.
We should not be enforcing such policy on the user. Additionally,
using the BLKRASET ioctl doesn't impose such a restriction. So
additionally we now expose identical behaviour through the two.

Issue also reported by Anton <cbou@mail.ru>
Signed-off-by: NJens Axboe <axboe@suse.de>

block/ll_rw_blk.c

@@ -3806,9 +3806,6 @@ queue_ra_store(struct request_queue *q, const char *page, size_t count)
 	ssize_t ret = queue_var_store(&ra_kb, page, count);
 
 	spin_lock_irq(q->queue_lock);
-	if (ra_kb > (q->max_sectors >> 1))
-		ra_kb = (q->max_sectors >> 1);
-
 	q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
 	spin_unlock_irq(q->queue_lock);