diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memcontrol.c | 105 | ||||
| -rw-r--r-- | mm/page-writeback.c | 22 | ||||
| -rw-r--r-- | mm/rmap.c | 20 |
3 files changed, 79 insertions, 68 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 23976fd885fd..d6ac0e33e150 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1536,12 +1536,8 @@ int mem_cgroup_swappiness(struct mem_cgroup *memcg) * start move here. */ -/* for quick checking without looking up memcg */ -atomic_t memcg_moving __read_mostly; - static void mem_cgroup_start_move(struct mem_cgroup *memcg) { - atomic_inc(&memcg_moving); atomic_inc(&memcg->moving_account); synchronize_rcu(); } @@ -1552,10 +1548,8 @@ static void mem_cgroup_end_move(struct mem_cgroup *memcg) * Now, mem_cgroup_clear_mc() may call this function with NULL. * We check NULL in callee rather than caller. */ - if (memcg) { - atomic_dec(&memcg_moving); + if (memcg) atomic_dec(&memcg->moving_account); - } } /* @@ -2204,41 +2198,52 @@ cleanup: return true; } -/* - * Used to update mapped file or writeback or other statistics. +/** + * mem_cgroup_begin_page_stat - begin a page state statistics transaction + * @page: page that is going to change accounted state + * @locked: &memcg->move_lock slowpath was taken + * @flags: IRQ-state flags for &memcg->move_lock * - * Notes: Race condition + * This function must mark the beginning of an accounted page state + * change to prevent double accounting when the page is concurrently + * being moved to another memcg: * - * Charging occurs during page instantiation, while the page is - * unmapped and locked in page migration, or while the page table is - * locked in THP migration. No race is possible. + * memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); + * if (TestClearPageState(page)) + * mem_cgroup_update_page_stat(memcg, state, -1); + * mem_cgroup_end_page_stat(memcg, locked, flags); * - * Uncharge happens to pages with zero references, no race possible. + * The RCU lock is held throughout the transaction. The fast path can + * get away without acquiring the memcg->move_lock (@locked is false) + * because page moving starts with an RCU grace period. * - * Charge moving between groups is protected by checking mm->moving - * account and taking the move_lock in the slowpath. + * The RCU lock also protects the memcg from being freed when the page + * state that is going to change is the only thing preventing the page + * from being uncharged. E.g. end-writeback clearing PageWriteback(), + * which allows migration to go ahead and uncharge the page before the + * account transaction might be complete. */ - -void __mem_cgroup_begin_update_page_stat(struct page *page, - bool *locked, unsigned long *flags) +struct mem_cgroup *mem_cgroup_begin_page_stat(struct page *page, + bool *locked, + unsigned long *flags) { struct mem_cgroup *memcg; struct page_cgroup *pc; + rcu_read_lock(); + + if (mem_cgroup_disabled()) + return NULL; + pc = lookup_page_cgroup(page); again: memcg = pc->mem_cgroup; if (unlikely(!memcg || !PageCgroupUsed(pc))) - return; - /* - * If this memory cgroup is not under account moving, we don't - * need to take move_lock_mem_cgroup(). Because we already hold - * rcu_read_lock(), any calls to move_account will be delayed until - * rcu_read_unlock(). - */ - VM_BUG_ON(!rcu_read_lock_held()); + return NULL; + + *locked = false; if (atomic_read(&memcg->moving_account) <= 0) - return; + return memcg; move_lock_mem_cgroup(memcg, flags); if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) { @@ -2246,36 +2251,40 @@ again: goto again; } *locked = true; + + return memcg; } -void __mem_cgroup_end_update_page_stat(struct page *page, unsigned long *flags) +/** + * mem_cgroup_end_page_stat - finish a page state statistics transaction + * @memcg: the memcg that was accounted against + * @locked: value received from mem_cgroup_begin_page_stat() + * @flags: value received from mem_cgroup_begin_page_stat() + */ +void mem_cgroup_end_page_stat(struct mem_cgroup *memcg, bool locked, + unsigned long flags) { - struct page_cgroup *pc = lookup_page_cgroup(page); + if (memcg && locked) + move_unlock_mem_cgroup(memcg, &flags); - /* - * It's guaranteed that pc->mem_cgroup never changes while - * lock is held because a routine modifies pc->mem_cgroup - * should take move_lock_mem_cgroup(). - */ - move_unlock_mem_cgroup(pc->mem_cgroup, flags); + rcu_read_unlock(); } -void mem_cgroup_update_page_stat(struct page *page, +/** + * mem_cgroup_update_page_stat - update page state statistics + * @memcg: memcg to account against + * @idx: page state item to account + * @val: number of pages (positive or negative) + * + * See mem_cgroup_begin_page_stat() for locking requirements. + */ +void mem_cgroup_update_page_stat(struct mem_cgroup *memcg, enum mem_cgroup_stat_index idx, int val) { - struct mem_cgroup *memcg; - struct page_cgroup *pc = lookup_page_cgroup(page); - unsigned long uninitialized_var(flags); - - if (mem_cgroup_disabled()) - return; - VM_BUG_ON(!rcu_read_lock_held()); - memcg = pc->mem_cgroup; - if (unlikely(!memcg || !PageCgroupUsed(pc))) - return; - this_cpu_add(memcg->stat->count[idx], val); + if (memcg) + this_cpu_add(memcg->stat->count[idx], val); } /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index ff6a5b07211e..19ceae87522d 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2327,11 +2327,12 @@ EXPORT_SYMBOL(clear_page_dirty_for_io); int test_clear_page_writeback(struct page *page) { struct address_space *mapping = page_mapping(page); - int ret; - bool locked; unsigned long memcg_flags; + struct mem_cgroup *memcg; + bool locked; + int ret; - mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags); + memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags); if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; @@ -2352,22 +2353,23 @@ int test_clear_page_writeback(struct page *page) ret = TestClearPageWriteback(page); } if (ret) { - mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); + mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_WRITEBACK); dec_zone_page_state(page, NR_WRITEBACK); inc_zone_page_state(page, NR_WRITTEN); } - mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags); + mem_cgroup_end_page_stat(memcg, locked, memcg_flags); return ret; } int __test_set_page_writeback(struct page *page, bool keep_write) { struct address_space *mapping = page_mapping(page); - int ret; - bool locked; unsigned long memcg_flags; + struct mem_cgroup *memcg; + bool locked; + int ret; - mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags); + memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags); if (mapping) { struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; @@ -2394,10 +2396,10 @@ int __test_set_page_writeback(struct page *page, bool keep_write) ret = TestSetPageWriteback(page); } if (!ret) { - mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK); + mem_cgroup_inc_page_stat(memcg, MEM_CGROUP_STAT_WRITEBACK); inc_zone_page_state(page, NR_WRITEBACK); } - mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags); + mem_cgroup_end_page_stat(memcg, locked, memcg_flags); return ret; } diff --git a/mm/rmap.c b/mm/rmap.c index 116a5053415b..f574046f77d4 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1042,15 +1042,16 @@ void page_add_new_anon_rmap(struct page *page, */ void page_add_file_rmap(struct page *page) { - bool locked; + struct mem_cgroup *memcg; unsigned long flags; + bool locked; - mem_cgroup_begin_update_page_stat(page, &locked, &flags); + memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); if (atomic_inc_and_test(&page->_mapcount)) { __inc_zone_page_state(page, NR_FILE_MAPPED); - mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED); + mem_cgroup_inc_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED); } - mem_cgroup_end_update_page_stat(page, &locked, &flags); + mem_cgroup_end_page_stat(memcg, locked, flags); } /** @@ -1061,9 +1062,10 @@ void page_add_file_rmap(struct page *page) */ void page_remove_rmap(struct page *page) { + struct mem_cgroup *uninitialized_var(memcg); bool anon = PageAnon(page); - bool locked; unsigned long flags; + bool locked; /* * The anon case has no mem_cgroup page_stat to update; but may @@ -1071,7 +1073,7 @@ void page_remove_rmap(struct page *page) * we hold the lock against page_stat move: so avoid it on anon. */ if (!anon) - mem_cgroup_begin_update_page_stat(page, &locked, &flags); + memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); /* page still mapped by someone else? */ if (!atomic_add_negative(-1, &page->_mapcount)) @@ -1096,8 +1098,7 @@ void page_remove_rmap(struct page *page) -hpage_nr_pages(page)); } else { __dec_zone_page_state(page, NR_FILE_MAPPED); - mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED); - mem_cgroup_end_update_page_stat(page, &locked, &flags); + mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED); } if (unlikely(PageMlocked(page))) clear_page_mlock(page); @@ -1110,10 +1111,9 @@ void page_remove_rmap(struct page *page) * Leaving it set also helps swapoff to reinstate ptes * faster for those pages still in swapcache. */ - return; out: if (!anon) - mem_cgroup_end_update_page_stat(page, &locked, &flags); + mem_cgroup_end_page_stat(memcg, locked, flags); } /* |