From: Wen Yang <wenyang@linux.alibaba.com>
Date: Tue, 14 Jan 2020 00:29:29 +0000 (-0800)
Subject: mm/page-writeback.c: improve arithmetic divisions
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0a5d1a7f64702c351d1f47ef159a0df8c71be0b0;p=linux.git

mm/page-writeback.c: improve arithmetic divisions

Use div64_ul() instead of do_div() if the divisor is unsigned long, to
avoid truncation to 32-bit on 64-bit platforms.

Link: http://lkml.kernel.org/r/20200102081442.8273-4-wenyang@linux.alibaba.com
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c74c6bd6540b3..2caf780a42e7a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1102,7 +1102,7 @@ static void wb_update_write_bandwidth(struct bdi_writeback *wb,
 	bw = written - min(written, wb->written_stamp);
 	bw *= HZ;
 	if (unlikely(elapsed > period)) {
-		do_div(bw, elapsed);
+		bw = div64_ul(bw, elapsed);
 		avg = bw;
 		goto out;
 	}