linux-kernel - [PATCH] kernel/power/snapshot.c: improve arithmetic divisions

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Message-Id: <20200103155458.21707-1-wenyang@linux.alibaba.com>
Date:   Fri,  3 Jan 2020 23:54:58 +0800
From:   Wen Yang <wenyang@...ux.alibaba.com>
To:     rjw@...ysocki.net, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>
Cc:     Wen Yang <wenyang@...ux.alibaba.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kernel/power/snapshot.c: improve arithmetic divisions

do_div() does a 64-by-32 division. Use div64_u64() instead of
do_div() if the divisor is u64, to avoid truncation to 32-bit.
This change also cleans up code a tad.

Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Len Brown <len.brown@...el.com>
Cc: Pavel Machek <pavel@....cz>
Cc: linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 kernel/power/snapshot.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 26b9168..8a6eaf7 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1566,9 +1566,7 @@ static unsigned long preallocate_image_highmem(unsigned long nr_pages)
  */
 static unsigned long __fraction(u64 x, u64 multiplier, u64 base)
 {
-	x *= multiplier;
-	do_div(x, base);
-	return (unsigned long)x;
+	return div64_u64(x * multiplier, base);
 }
 
 static unsigned long preallocate_highmem_fraction(unsigned long nr_pages,
-- 
1.8.3.1