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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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7
mm/filemap.c
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@@ -176,8 +176,7 @@ static void page_cache_tree_delete(struct address_space *mapping,
/*
* Delete a page from the page cache and free it. Caller has to make
* sure the page is locked and that nobody else uses it - or that usage
* is safe. The caller must hold the mapping's tree_lock and
* lock_page_memcg().
* is safe. The caller must hold the mapping's tree_lock.
*/
void __delete_from_page_cache(struct page *page, void *shadow)
{
@@ -260,11 +259,9 @@ void delete_from_page_cache(struct page *page)
freepage = mapping->a_ops->freepage;
lock_page_memcg(page);
spin_lock_irqsave(&mapping->tree_lock, flags);
__delete_from_page_cache(page, NULL);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
unlock_page_memcg(page);
if (freepage)
freepage(page);
@@ -557,7 +554,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
new->mapping = mapping;
new->index = offset;
lock_page_memcg(old);
spin_lock_irqsave(&mapping->tree_lock, flags);
__delete_from_page_cache(old, NULL);
error = radix_tree_insert(&mapping->page_tree, offset, new);
@@ -572,7 +568,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
if (PageSwapBacked(new))
__inc_zone_page_state(new, NR_SHMEM);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
unlock_page_memcg(old);
mem_cgroup_migrate(old, new);
radix_tree_preload_end();
if (freepage)