On Mon 19-03-12 16:59:47, KAMEZAWA Hiroyuki wrote:
> In order to encode pc->mem_cgroup and pc->flags to be in a word,
> access function to pc->mem_cgroup is required.
>
> This patch replaces access to pc->mem_cgroup with
> pc_to_mem_cgroup(pc) : pc->mem_cgroup
> pc_set_mem_cgroup(pc, memcg) : pc->mem_cgroup = memcg
>
> Following patch will remove pc->mem_cgroup.
Acked-by: Michal Hocko <mhocko@xxxxxxx>
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> include/linux/page_cgroup.h | 12 +++++++
> mm/memcontrol.c | 69 ++++++++++++++++++++++--------------------
> 2 files changed, 48 insertions(+), 33 deletions(-)
>
> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
> index a88cdba..92768cb 100644
> --- a/include/linux/page_cgroup.h
> +++ b/include/linux/page_cgroup.h
> @@ -82,6 +82,18 @@ static inline void unlock_page_cgroup(struct page_cgroup *pc)
> bit_spin_unlock(PCG_LOCK, &pc->flags);
> }
>
> +
> +static inline struct mem_cgroup* pc_to_mem_cgroup(struct page_cgroup *pc)
> +{
> + return pc->mem_cgroup;
> +}
> +
> +static inline void
> +pc_set_mem_cgroup(struct page_cgroup *pc, struct mem_cgroup *memcg)
> +{
> + pc->mem_cgroup = memcg;
> +}
> +
> #else /* CONFIG_CGROUP_MEM_RES_CTLR */
> struct page_cgroup;
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c65e6bc..124fec9 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1014,9 +1014,9 @@ struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
> /*
> * Following LRU functions are allowed to be used without PCG_LOCK.
> * Operations are called by routine of global LRU independently from memcg.
> - * What we have to take care of here is validness of pc->mem_cgroup.
> + * What we have to take care of here is validness of pc's mem_cgroup.
> *
> - * Changes to pc->mem_cgroup happens when
> + * Changes to pc's mem_cgroup happens when
> * 1. charge
> * 2. moving account
> * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
> @@ -1048,7 +1048,7 @@ struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
> return &zone->lruvec;
>
> pc = lookup_page_cgroup(page);
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
>
> /*
> * Surreptitiously switch any uncharged page to root:
> @@ -1057,10 +1057,12 @@ struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
> *
> * Our caller holds lru_lock, and PageCgroupUsed is updated
> * under page_cgroup lock: between them, they make all uses
> - * of pc->mem_cgroup safe.
> + * of pc's mem_cgroup safe.
> */
> - if (!PageCgroupUsed(pc) && memcg != root_mem_cgroup)
> - pc->mem_cgroup = memcg = root_mem_cgroup;
> + if (!PageCgroupUsed(pc) && memcg != root_mem_cgroup) {
> + pc_set_mem_cgroup(pc, root_mem_cgroup);
> + memcg = root_mem_cgroup;
> + }
>
> mz = page_cgroup_zoneinfo(memcg, page);
> /* compound_order() is stabilized through lru_lock */
> @@ -1088,7 +1090,7 @@ void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
> return;
>
> pc = lookup_page_cgroup(page);
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> VM_BUG_ON(!memcg);
> mz = page_cgroup_zoneinfo(memcg, page);
> /* huge page split is done under lru_lock. so, we have no races. */
> @@ -1235,9 +1237,9 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
> pc = lookup_page_cgroup(page);
> if (!PageCgroupUsed(pc))
> return NULL;
> - /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
> + /* Ensure pc's mem_cgroup is visible after reading PCG_USED. */
> smp_rmb();
> - mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
> + mz = page_cgroup_zoneinfo(pc_to_mem_cgroup(pc), page);
> return &mz->reclaim_stat;
> }
>
> @@ -1314,7 +1316,7 @@ static void mem_cgroup_end_move(struct mem_cgroup *memcg)
> *
> * mem_cgroup_stolen() - checking whether a cgroup is mc.from or not. This
> * is used for avoiding races in accounting. If true,
> - * pc->mem_cgroup may be overwritten.
> + * pc's mem_cgroup may be overwritten.
> *
> * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
> * under hierarchy of moving cgroups. This is for
> @@ -1887,8 +1889,8 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask)
> * file-stat operations happen after a page is attached to radix-tree. There
> * are no race with "charge".
> *
> - * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
> - * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
> + * Considering "uncharge", we know that memcg doesn't clear pc's mem_cgroup
> + * at "uncharge" intentionally. So, we always see valid pc's mem_cgroup even
> * if there are race with "uncharge". Statistics itself is properly handled
> * by flags.
> *
> @@ -1905,7 +1907,7 @@ void __mem_cgroup_begin_update_page_stat(struct page *page,
>
> pc = lookup_page_cgroup(page);
> again:
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> if (unlikely(!memcg || !PageCgroupUsed(pc)))
> return;
> /*
> @@ -1918,7 +1920,7 @@ again:
> return;
>
> move_lock_mem_cgroup(memcg, flags);
> - if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) {
> + if (memcg != pc_to_mem_cgroup(pc) || !PageCgroupUsed(pc)) {
> move_unlock_mem_cgroup(memcg, flags);
> goto again;
> }
> @@ -1930,11 +1932,11 @@ void __mem_cgroup_end_update_page_stat(struct page *page, unsigned long *flags)
> struct page_cgroup *pc = lookup_page_cgroup(page);
>
> /*
> - * It's guaranteed that pc->mem_cgroup never changes while
> - * lock is held because a routine modifies pc->mem_cgroup
> + * It's guaranteed that pc's mem_cgroup never changes while
> + * lock is held because a routine modifies pc's mem_cgroup
> * should take move_lock_page_cgroup().
> */
> - move_unlock_mem_cgroup(pc->mem_cgroup, flags);
> + move_unlock_mem_cgroup(pc_to_mem_cgroup(pc), flags);
> }
>
> void mem_cgroup_update_page_stat(struct page *page,
> @@ -1947,7 +1949,7 @@ void mem_cgroup_update_page_stat(struct page *page,
> if (mem_cgroup_disabled())
> return;
>
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> if (unlikely(!memcg || !PageCgroupUsed(pc)))
> return;
>
> @@ -2244,7 +2246,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> * has TIF_MEMDIE, this function returns -EINTR while writing root_mem_cgroup
> * to *ptr. There are two reasons for this. 1: fatal threads should quit as soon
> * as possible without any hazards. 2: all pages should have a valid
> - * pc->mem_cgroup. If mm is NULL and the caller doesn't pass a valid memcg
> + * pc's mem_cgroup. If mm is NULL and the caller doesn't pass a valid memcg
> * pointer, that is treated as a charge to root_mem_cgroup.
> *
> * So __mem_cgroup_try_charge() will return
> @@ -2437,7 +2439,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> pc = lookup_page_cgroup(page);
> lock_page_cgroup(pc);
> if (PageCgroupUsed(pc)) {
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> if (memcg && !css_tryget(&memcg->css))
> memcg = NULL;
> } else if (PageSwapCache(page)) {
> @@ -2489,11 +2491,11 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
> }
> }
>
> - pc->mem_cgroup = memcg;
> + pc_set_mem_cgroup(pc, memcg);
> /*
> * We access a page_cgroup asynchronously without lock_page_cgroup().
> - * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
> - * is accessed after testing USED bit. To make pc->mem_cgroup visible
> + * Especially when a page_cgroup is taken from a page, pc's mem_cgroup
> + * is accessed after testing USED bit. To make pc's mem_cgroup visible
> * before USED bit, we need memory barrier here.
> * See mem_cgroup_add_lru_list(), etc.
> */
> @@ -2538,13 +2540,14 @@ void mem_cgroup_split_huge_fixup(struct page *head)
> {
> struct page_cgroup *head_pc = lookup_page_cgroup(head);
> struct page_cgroup *pc;
> + struct mem_cgroup *memcg = pc_to_mem_cgroup(head_pc);
> int i;
>
> if (mem_cgroup_disabled())
> return;
> for (i = 1; i < HPAGE_PMD_NR; i++) {
> pc = head_pc + i;
> - pc->mem_cgroup = head_pc->mem_cgroup;
> + pc_set_mem_cgroup(pc, memcg);
> smp_wmb();/* see __commit_charge() */
> pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
> }
> @@ -2595,7 +2598,7 @@ static int mem_cgroup_move_account(struct page *page,
> lock_page_cgroup(pc);
>
> ret = -EINVAL;
> - if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
> + if (!PageCgroupUsed(pc) || pc_to_mem_cgroup(pc) != from)
> goto unlock;
>
> move_lock_mem_cgroup(from, &flags);
> @@ -2613,7 +2616,7 @@ static int mem_cgroup_move_account(struct page *page,
> __mem_cgroup_cancel_charge(from, nr_pages);
>
> /* caller should have done css_get */
> - pc->mem_cgroup = to;
> + pc_set_mem_cgroup(pc, to);
> mem_cgroup_charge_statistics(to, anon, nr_pages);
> /*
> * We charges against "to" which may not have any tasks. Then, "to"
> @@ -2956,7 +2959,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
>
> lock_page_cgroup(pc);
>
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
>
> if (!PageCgroupUsed(pc))
> goto unlock_out;
> @@ -2992,7 +2995,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
>
> ClearPageCgroupUsed(pc);
> /*
> - * pc->mem_cgroup is not cleared here. It will be accessed when it's
> + * pc's mem_cgroup is not cleared here. It will be accessed when it's
> * freed from LRU. This is safe because uncharged page is expected not
> * to be reused (freed soon). Exception is SwapCache, it's handled by
> * special functions.
> @@ -3214,7 +3217,7 @@ int mem_cgroup_prepare_migration(struct page *page,
> pc = lookup_page_cgroup(page);
> lock_page_cgroup(pc);
> if (PageCgroupUsed(pc)) {
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> css_get(&memcg->css);
> /*
> * At migrating an anonymous page, its mapcount goes down
> @@ -3359,7 +3362,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
> pc = lookup_page_cgroup(oldpage);
> /* fix accounting on old pages */
> lock_page_cgroup(pc);
> - memcg = pc->mem_cgroup;
> + memcg = pc_to_mem_cgroup(pc);
> mem_cgroup_charge_statistics(memcg, false, -1);
> ClearPageCgroupUsed(pc);
> unlock_page_cgroup(pc);
> @@ -3370,7 +3373,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
> /*
> * Even if newpage->mapping was NULL before starting replacement,
> * the newpage may be on LRU(or pagevec for LRU) already. We lock
> - * LRU while we overwrite pc->mem_cgroup.
> + * LRU while we overwrite pc's mem_cgroup.
> */
> __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true);
> }
> @@ -3406,7 +3409,7 @@ void mem_cgroup_print_bad_page(struct page *page)
> pc = lookup_page_cgroup_used(page);
> if (pc) {
> printk(KERN_ALERT "pc:%p pc->flags:%lx pc->mem_cgroup:%p\n",
> - pc, pc->flags, pc->mem_cgroup);
> + pc, pc->flags, pc_to_mem_cgroup(pc));
> }
> }
> #endif
> @@ -5197,7 +5200,7 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
> * mem_cgroup_move_account() checks the pc is valid or not under
> * the lock.
> */
> - if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
> + if (PageCgroupUsed(pc) && pc_to_mem_cgroup(pc) == mc.from) {
> ret = MC_TARGET_PAGE;
> if (target)
> target->page = page;
> --
> 1.7.4.1
>
>
> --
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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