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mm: remove unnecessary uses of lock_page_memcg()

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There are several users that nest lock_page_memcg() inside lock_page()
to prevent page->mem_cgroup from changing.  But the page lock prevents
pages from moving between cgroups, so that is unnecessary overhead.

Remove lock_page_memcg() in contexts with locked contexts and fix the
debug code in the page stat functions to be okay with the page lock.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner
2016-03-15 14:57:25 -07:00
committed by Linus Torvalds
parent 62cccb8c8e
commit fdf1cdb91b
5 changed files with 8 additions and 20 deletions
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2
mm/page-writeback.c
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@@ -2700,7 +2700,6 @@ int clear_page_dirty_for_io(struct page *page)
* always locked coming in here, so we get the desired
* exclusion.
*/
lock_page_memcg(page);
wb = unlocked_inode_to_wb_begin(inode, &locked);
if (TestClearPageDirty(page)) {
mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY);
@@ -2709,7 +2708,6 @@ int clear_page_dirty_for_io(struct page *page)
ret = 1;
}
unlocked_inode_to_wb_end(inode, locked);
unlock_page_memcg(page);
return ret;
}
return TestClearPageDirty(page);