linux-kernel - Re: [PATCH] mm: simplify get_next_ra

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Date:   Sun, 28 Oct 2018 14:27:22 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Gao Xiang <hsiangkao@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: simplify get_next_ra_size

Looks good to me, thanks!

Reviewed-by: Fengguang Wu <fengguang.wu@...el.com>

On Sun, Oct 28, 2018 at 02:13:26PM +0800, Gao Xiang wrote:
>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
>