[PATCH 5/5] readahead: remove size limit on read_ahead_kb

[Wu Fengguang <wfg@mail.ustc.edu.cn>]

Remove the unnecessary size limit on setting read_ahead_kb.

Also make possible large values harmless. The stock readahead
is protected by always consulting the avaiable memory before
applying this number. Other readahead paths have already did so.

read_ahead_kb used to be guarded by the queue's max_sectors,
which can be too rigid because some devices set max_sectors to
small values like 64kb. That leads to many user complains.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---


 block/ll_rw_blk.c |    5 -----
 1 files changed, 5 deletions(-)

--- linux-2.6.17-rc6-mm1.orig/block/ll_rw_blk.c
+++ linux-2.6.17-rc6-mm1/block/ll_rw_blk.c
@@ -3810,12 +3810,7 @@ queue_ra_store(struct request_queue *q, 
 	unsigned long ra_kb;
 	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);
 
 	return ret;
 }
--- linux-2.6.17-rc6-mm1.orig/mm/readahead.c
+++ linux-2.6.17-rc6-mm1/mm/readahead.c
@@ -156,7 +156,7 @@ EXPORT_SYMBOL_GPL(file_ra_state_init);
  */
 static inline unsigned long get_max_readahead(struct file_ra_state *ra)
 {
-	return ra->ra_pages;
+	return max_sane_readahead(ra->ra_pages);
 }
 
 static inline unsigned long get_min_readahead(struct file_ra_state *ra)

--
-
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