readahead: remove the limit max_sectors_kb imposed on max_readahead_kb

Remove the size limit max_sectors_kb imposed on max_readahead_kb.

The size restriction is unreasonable.  Especially when max_sectors_kb cannot
grow larger than max_hw_sectors_kb, which can be rather small for some disk
drives.

Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index d875673..a83823f 100644 (file)
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3928,7 +3928,6 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
                        max_hw_sectors_kb = q->max_hw_sectors >> 1,
                        page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
        ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
-       int ra_kb;
 
        if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
                return -EINVAL;
@@ -3937,14 +3936,6 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
         * values synchronously:
         */
        spin_lock_irq(q->queue_lock);
-       /*
-        * Trim readahead window as well, if necessary:
-        */
-       ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
-       if (ra_kb > max_sectors_kb)
-               q->backing_dev_info.ra_pages =
-                               max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
-
        q->max_sectors = max_sectors_kb << 1;
        spin_unlock_irq(q->queue_lock);