linux-kernel - [PATCH] mm: simplify get_next_ra

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Date:   Sun, 28 Oct 2018 14:13:26 +0800
From:   Gao Xiang <hsiangkao@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Fengguang Wu <fengguang.wu@...el.com>,
        Gao Xiang <hsiangkao@....com>
Subject: [PATCH] mm: simplify get_next_ra_size

It's a trivial simplification for get_next_ra_size and
clear enough for humans to understand.

It also fixes potential overflow if ra->size(< ra_pages) is too large.

Cc: Fengguang Wu <fengguang.wu@...el.com>
Signed-off-by: Gao Xiang <hsiangkao@....com>
---
 mm/readahead.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index 4e63014..205ac34 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -272,17 +272,15 @@ static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
  *  return it as the new window size.
  */
 static unsigned long get_next_ra_size(struct file_ra_state *ra,
-						unsigned long max)
+				      unsigned long max)
 {
 	unsigned long cur = ra->size;
-	unsigned long newsize;
 
 	if (cur < max / 16)
-		newsize = 4 * cur;
-	else
-		newsize = 2 * cur;
-
-	return min(newsize, max);
+		return 4 * cur;
+	if (cur <= max / 2)
+		return 2 * cur;
+	return max;
 }
 
 /*
-- 
2.7.4