From: Andrew Morton <akpm@linux-foundation.org>
To: tj@kernel.org, cai@lca.pw, axboe@kernel.dk,
wenyang@linux.alibaba.com, akpm@linux-foundation.org,
linux-mm@kvack.org, mm-commits@vger.kernel.org,
torvalds@linux-foundation.org
Subject: [patch 08/11] mm/page-writeback.c: use div64_ul() for u64-by-unsigned-long divide
Date: Mon, 13 Jan 2020 16:29:26 -0800 [thread overview]
Message-ID: <20200114002926.Cskkh%akpm__4412.23914256028$1578961888$gmane$org@linux-foundation.org> (raw)
In-Reply-To: <20200113162831.f7d69e11e9e673c40005c9b0@linux-foundation.org>
From: Wen Yang <wenyang@linux.alibaba.com>
Subject: mm/page-writeback.c: use div64_ul() for u64-by-unsigned-long divide
The two variables 'numerator' and 'denominator', though they are declared
as long, they should actually be unsigned long (according to the
implementation of the fprop_fraction_percpu() function)
And do_div() does a 64-by-32 division, while the divisor 'denominator' is
unsigned long, thus 64-bit on 64-bit platforms. Hence the proper function
to call is div64_ul().
Link: http://lkml.kernel.org/r/20200102081442.8273-3-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>
---
mm/page-writeback.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/page-writeback.c~mm-page-writebackc-use-div64_ul-for-u64-by-unsigned-long-divide
+++ a/mm/page-writeback.c
@@ -766,7 +766,7 @@ static unsigned long __wb_calc_thresh(st
struct wb_domain *dom = dtc_dom(dtc);
unsigned long thresh = dtc->thresh;
u64 wb_thresh;
- long numerator, denominator;
+ unsigned long numerator, denominator;
unsigned long wb_min_ratio, wb_max_ratio;
/*
@@ -777,7 +777,7 @@ static unsigned long __wb_calc_thresh(st
wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100;
wb_thresh *= numerator;
- do_div(wb_thresh, denominator);
+ wb_thresh = div64_ul(wb_thresh, denominator);
wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio);
_
next prev parent reply other threads:[~2020-01-14 0:29 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 0:28 incoming Andrew Morton
2020-01-14 0:29 ` [patch 01/11] mm, thp: tweak reclaim/compaction effort of local-only and all-node allocations Andrew Morton
2020-01-14 0:29 ` Andrew Morton
2020-01-14 2:16 ` Linus Torvalds
2020-01-14 8:05 ` Vlastimil Babka
2020-01-14 8:46 ` Michal Hocko
2020-01-14 0:29 ` [patch 02/11] mm/memory_hotplug: don't free usage map when removing a re-added early section Andrew Morton
2020-01-14 0:29 ` [patch 03/11] mm/huge_memory.c: thp: fix conflict of above-47bit hint address and PMD alignment Andrew Morton
2020-01-14 0:29 ` Andrew Morton
2020-01-14 0:29 ` [patch 04/11] mm/shmem.c: thp, shmem: " Andrew Morton
2020-01-14 0:29 ` [patch 05/11] mm: memcg/slab: fix percpu slab vmstats flushing Andrew Morton
2020-01-14 0:29 ` Andrew Morton
2020-01-14 0:29 ` [patch 06/11] mm, debug_pagealloc: don't rely on static keys too early Andrew Morton
2020-01-14 0:29 ` [patch 07/11] mm/page-writeback.c: avoid potential division by zero in wb_min_max_ratio() Andrew Morton
2020-01-14 0:29 ` Andrew Morton
2020-01-14 0:29 ` Andrew Morton [this message]
2020-01-14 0:29 ` [patch 08/11] mm/page-writeback.c: use div64_ul() for u64-by-unsigned-long divide Andrew Morton
2020-01-14 0:29 ` [patch 09/11] mm/page-writeback.c: improve arithmetic divisions Andrew Morton
2020-01-14 0:29 ` [patch 10/11] mm: memcg/slab: call flush_memcg_workqueue() only if memcg workqueue is valid Andrew Morton
2020-01-14 0:29 ` Andrew Morton
2020-01-14 0:29 ` [patch 11/11] mm: khugepaged: add trace status description for SCAN_PAGE_HAS_PRIVATE Andrew Morton
2020-01-14 0:29 ` Andrew Morton
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