In mem_cgroup_move_parent(), we can avoid the get_page_unless_zero() call by taking a page reference under protection of the zone LRU lock in mem_cgroup_force_empty_list(). In mc_handle_present_pte(), the page count is already known to be nonzero as there is a PTE pointing to it and the page table lock is held. Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> --- mm/memcontrol.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e013b8e..f9439ef 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2649,7 +2649,7 @@ out: } /* - * move charges to its parent. + * move charges to its parent. Caller must hold a reference on page. */ static int mem_cgroup_move_parent(struct page *page, @@ -2669,10 +2669,8 @@ static int mem_cgroup_move_parent(struct page *page, return -EINVAL; ret = -EBUSY; - if (!get_page_unless_zero(page)) - goto out; if (isolate_lru_page(page)) - goto put; + goto out; nr_pages = hpage_nr_pages(page); @@ -2692,8 +2690,6 @@ static int mem_cgroup_move_parent(struct page *page, compound_unlock_irqrestore(page, flags); put_back: putback_lru_page(page); -put: - put_page(page); out: return ret; } @@ -3732,11 +3728,12 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *mem, spin_unlock_irqrestore(&zone->lru_lock, flags); continue; } - spin_unlock_irqrestore(&zone->lru_lock, flags); - page = lookup_cgroup_page(pc); + get_page(page); + spin_unlock_irqrestore(&zone->lru_lock, flags); ret = mem_cgroup_move_parent(page, pc, mem, GFP_KERNEL); + put_page(page); if (ret == -ENOMEM) break; @@ -5133,9 +5130,12 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma, } else if (!move_file()) /* we ignore mapcount for file pages */ return NULL; - if (!get_page_unless_zero(page)) - return NULL; + /* + * The page reference count is guaranteed to be nonzero since + * ptent points to that page and the page table lock is held. + */ + get_page(page); return page; } -- 1.7.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>