From ae41be374293e70e1ed441d986afcc6e744ef9d9 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Thu, 7 Feb 2008 00:14:10 -0800 Subject: [PATCH] bugfix for memory cgroup controller: migration under memory controller fix While using memory control cgroup, page-migration under it works as following. == 1. uncharge all refs at try to unmap. 2. charge regs again remove_migration_ptes() == This is simple but has following problems. == The page is uncharged and charged back again if *mapped*. - This means that cgroup before migration can be different from one after migration - If page is not mapped but charged as page cache, charge is just ignored (because not mapped, it will not be uncharged before migration) This is memory leak. == This patch tries to keep memory cgroup at page migration by increasing one refcnt during it. 3 functions are added. mem_cgroup_prepare_migration() --- increase refcnt of page->page_cgroup mem_cgroup_end_migration() --- decrease refcnt of page->page_cgroup mem_cgroup_page_migration() --- copy page->page_cgroup from old page to new page. During migration - old page is under PG_locked. - new page is under PG_locked, too. - both old page and new page is not on LRU. These 3 facts guarantee that page_cgroup() migration has no race. Tested and worked well in x86_64/fake-NUMA box. Signed-off-by: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Pavel Emelianov Cc: Paul Menage Cc: Peter Zijlstra Cc: "Eric W. Biederman" Cc: Nick Piggin Cc: Kirill Korotaev Cc: Herbert Poetzl Cc: David Rientjes Cc: Vaidyanathan Srinivasan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 19 +++++++++++++++++ mm/memcontrol.c | 43 ++++++++++++++++++++++++++++++++++++++ mm/migrate.c | 13 +++++++++--- 3 files changed, 72 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 42536c737d..4ec712967f 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -60,6 +60,10 @@ static inline void mem_cgroup_uncharge_page(struct page *page) mem_cgroup_uncharge(page_get_page_cgroup(page)); } +extern int mem_cgroup_prepare_migration(struct page *page); +extern void mem_cgroup_end_migration(struct page *page); +extern void mem_cgroup_page_migration(struct page *page, struct page *newpage); + #else /* CONFIG_CGROUP_MEM_CONT */ static inline void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p) @@ -117,6 +121,21 @@ static inline int task_in_mem_cgroup(struct task_struct *task, return 1; } +static inline int mem_cgroup_prepare_migration(struct page *page) +{ + return 0; +} + +static inline void mem_cgroup_end_migration(struct page *page) +{ +} + +static inline void +mem_cgroup_page_migration(struct page *page, struct page *newpage) +{ +} + + #endif /* CONFIG_CGROUP_MEM_CONT */ #endif /* _LINUX_MEMCONTROL_H */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3270ce7375..128f45c16f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -492,6 +492,49 @@ void mem_cgroup_uncharge(struct page_cgroup *pc) } } } +/* + * Returns non-zero if a page (under migration) has valid page_cgroup member. + * Refcnt of page_cgroup is incremented. + */ + +int mem_cgroup_prepare_migration(struct page *page) +{ + struct page_cgroup *pc; + int ret = 0; + lock_page_cgroup(page); + pc = page_get_page_cgroup(page); + if (pc && atomic_inc_not_zero(&pc->ref_cnt)) + ret = 1; + unlock_page_cgroup(page); + return ret; +} + +void mem_cgroup_end_migration(struct page *page) +{ + struct page_cgroup *pc = page_get_page_cgroup(page); + mem_cgroup_uncharge(pc); +} +/* + * We know both *page* and *newpage* are now not-on-LRU and Pg_locked. + * And no race with uncharge() routines because page_cgroup for *page* + * has extra one reference by mem_cgroup_prepare_migration. + */ + +void mem_cgroup_page_migration(struct page *page, struct page *newpage) +{ + struct page_cgroup *pc; +retry: + pc = page_get_page_cgroup(page); + if (!pc) + return; + if (clear_page_cgroup(page, pc) != pc) + goto retry; + pc->page = newpage; + lock_page_cgroup(newpage); + page_assign_page_cgroup(newpage, pc); + unlock_page_cgroup(newpage); + return; +} int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp) { diff --git a/mm/migrate.c b/mm/migrate.c index 7637941446..a73504ff5a 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -593,9 +593,10 @@ static int move_to_new_page(struct page *newpage, struct page *page) else rc = fallback_migrate_page(mapping, newpage, page); - if (!rc) + if (!rc) { + mem_cgroup_page_migration(page, newpage); remove_migration_ptes(page, newpage); - else + } else newpage->mapping = NULL; unlock_page(newpage); @@ -614,6 +615,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, int *result = NULL; struct page *newpage = get_new_page(page, private, &result); int rcu_locked = 0; + int charge = 0; if (!newpage) return -ENOMEM; @@ -673,14 +675,19 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, goto rcu_unlock; } + charge = mem_cgroup_prepare_migration(page); /* Establish migration ptes or remove ptes */ try_to_unmap(page, 1); if (!page_mapped(page)) rc = move_to_new_page(newpage, page); - if (rc) + if (rc) { remove_migration_ptes(page, page); + if (charge) + mem_cgroup_end_migration(page); + } else if (charge) + mem_cgroup_end_migration(newpage); rcu_unlock: if (rcu_locked) rcu_read_unlock(); -- 2.39.5