linux-kernel - [PATCH v2] mm: cleanup some useless code

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Message-Id: <20191210160450.3395-1-pilgrimtao@gmail.com>
Date:   Tue, 10 Dec 2019 08:04:50 -0800
From:   chengkaitao <pilgrimtao@...il.com>
To:     hannes@...xchg.org
Cc:     mhocko@...nel.org, vdavydov.dev@...il.com,
        akpm@...ux-foundation.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        smuchun@...il.com, Kaitao Cheng <pilgrimtao@...il.com>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH v2] mm: cleanup some useless code

From: Kaitao Cheng <pilgrimtao@...il.com>

Compound pages handling in mem_cgroup_migrate is more convoluted than
necessary. The state is duplicated in compound variable and the same
could be achieved by PageTransHuge check which is trivial and
hpage_nr_pages is already PageTransHuge aware.

It is much simpler to just use hpage_nr_pages for nr_pages and replace
the local variable by PageTransHuge check directly

Signed-off-by: Kaitao Cheng <pilgrimtao@...il.com>
Acked-by: Michal Hocko <mhocko@...e.com>
---
Change in v2:
	Update commit message

 mm/memcontrol.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bc01423277c5..870284d3ee9d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6678,7 +6678,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 {
 	struct mem_cgroup *memcg;
 	unsigned int nr_pages;
-	bool compound;
 	unsigned long flags;
 
 	VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
@@ -6700,8 +6699,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 		return;
 
 	/* Force-charge the new page. The old one will be freed soon */
-	compound = PageTransHuge(newpage);
-	nr_pages = compound ? hpage_nr_pages(newpage) : 1;
+	nr_pages = hpage_nr_pages(newpage);
 
 	page_counter_charge(&memcg->memory, nr_pages);
 	if (do_memsw_account())
@@ -6711,7 +6709,8 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 	commit_charge(newpage, memcg, false);
 
 	local_irq_save(flags);
-	mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages);
+	mem_cgroup_charge_statistics(memcg, newpage, PageTransHuge(newpage),
+			nr_pages);
 	memcg_check_events(memcg, newpage);
 	local_irq_restore(flags);
 }
-- 
2.20.1