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From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@suse.com>,
	Shakeel Butt <shakeelb@google.com>, Roman Gushchin <guro@fb.com>,
	linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH] mm: page-writeback: simplify memcg handling in test_clear_page_writeback()
Date: Tue,  9 Feb 2021 16:45:43 -0500	[thread overview]
Message-ID: <20210209214543.112655-1-hannes@cmpxchg.org> (raw)

Page writeback doesn't hold a page reference, which allows truncate to
free a page the second PageWriteback is cleared. This used to require
special attention in test_clear_page_writeback(), where we had to be
careful not to rely on the unstable page->memcg binding and look up
all the necessary information before clearing the writeback flag.

Since commit 073861ed77b6 ("mm: fix VM_BUG_ON(PageTail) and
BUG_ON(PageWriteback)") test_clear_page_writeback() is called with an
explicit reference on the page, and this dance is no longer needed.

Use unlock_page_memcg() and dec_lruvec_page_stat() directly.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/page-writeback.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index eb34d204d4ee..f6c2c3165d4d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2722,12 +2722,9 @@ EXPORT_SYMBOL(clear_page_dirty_for_io);
 int test_clear_page_writeback(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
-	struct mem_cgroup *memcg;
-	struct lruvec *lruvec;
 	int ret;
 
-	memcg = lock_page_memcg(page);
-	lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
+	lock_page_memcg(page);
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		struct inode *inode = mapping->host;
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
@@ -2755,11 +2752,11 @@ int test_clear_page_writeback(struct page *page)
 		ret = TestClearPageWriteback(page);
 	}
 	if (ret) {
-		dec_lruvec_state(lruvec, NR_WRITEBACK);
+		dec_lruvec_page_state(page, NR_WRITEBACK);
 		dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
 		inc_node_page_state(page, NR_WRITTEN);
 	}
-	__unlock_page_memcg(memcg);
+	unlock_page_memcg(page);
 	return ret;
 }
 
-- 
2.30.0


WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
To: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>,
	Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	kernel-team-b10kYP2dOMg@public.gmane.org
Subject: [PATCH] mm: page-writeback: simplify memcg handling in test_clear_page_writeback()
Date: Tue,  9 Feb 2021 16:45:43 -0500	[thread overview]
Message-ID: <20210209214543.112655-1-hannes@cmpxchg.org> (raw)

Page writeback doesn't hold a page reference, which allows truncate to
free a page the second PageWriteback is cleared. This used to require
special attention in test_clear_page_writeback(), where we had to be
careful not to rely on the unstable page->memcg binding and look up
all the necessary information before clearing the writeback flag.

Since commit 073861ed77b6 ("mm: fix VM_BUG_ON(PageTail) and
BUG_ON(PageWriteback)") test_clear_page_writeback() is called with an
explicit reference on the page, and this dance is no longer needed.

Use unlock_page_memcg() and dec_lruvec_page_stat() directly.

Signed-off-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
---
 mm/page-writeback.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index eb34d204d4ee..f6c2c3165d4d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2722,12 +2722,9 @@ EXPORT_SYMBOL(clear_page_dirty_for_io);
 int test_clear_page_writeback(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
-	struct mem_cgroup *memcg;
-	struct lruvec *lruvec;
 	int ret;
 
-	memcg = lock_page_memcg(page);
-	lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
+	lock_page_memcg(page);
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		struct inode *inode = mapping->host;
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
@@ -2755,11 +2752,11 @@ int test_clear_page_writeback(struct page *page)
 		ret = TestClearPageWriteback(page);
 	}
 	if (ret) {
-		dec_lruvec_state(lruvec, NR_WRITEBACK);
+		dec_lruvec_page_state(page, NR_WRITEBACK);
 		dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
 		inc_node_page_state(page, NR_WRITTEN);
 	}
-	__unlock_page_memcg(memcg);
+	unlock_page_memcg(page);
 	return ret;
 }
 
-- 
2.30.0


             reply	other threads:[~2021-02-10  1:16 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-09 21:45 Johannes Weiner [this message]
2021-02-09 21:45 ` [PATCH] mm: page-writeback: simplify memcg handling in test_clear_page_writeback() Johannes Weiner
2021-02-10  5:16 ` Hugh Dickins
2021-02-10  5:16   ` Hugh Dickins
2021-02-10  5:16   ` Hugh Dickins
2021-02-10 16:22   ` Hugh Dickins
2021-02-10 16:22     ` Hugh Dickins
2021-02-10 16:22     ` Hugh Dickins
2021-02-10 17:44     ` [PATCH v2] " Johannes Weiner
2021-02-10 17:44       ` Johannes Weiner
2021-02-10 20:14       ` Hugh Dickins
2021-02-10 20:14         ` Hugh Dickins
2021-02-10 20:14         ` Hugh Dickins
2021-02-10 22:59       ` Shakeel Butt
2021-02-10 22:59         ` Shakeel Butt
2021-02-10 22:59         ` Shakeel Butt
2021-02-11  0:33         ` Johannes Weiner
2021-02-11  0:33           ` Johannes Weiner
2021-02-12 10:05       ` Michal Hocko
2021-02-12 10:05         ` Michal Hocko
2021-02-10 13:46 ` [PATCH] " Shakeel Butt
2021-02-10 13:46   ` Shakeel Butt
2021-02-10 13:46   ` Shakeel Butt

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