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Date: Thu, 19 Jul 2012 11:29:28 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Cc: linux-mm@...ck.org, Johannes Weiner <hannes@...xchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
Gavin Shan <shangw@...ux.vnet.ibm.com>,
Bob Liu <lliubbo@...il.com>
Subject: Re: [PATCH v2] mm/memcg: use exist interface to get css from memcg
On Wed 18-07-12 19:08:54, Wanpeng Li wrote:
> use exist interface mem_cgroup_css instead of &mem->css.
This interface has been added to enable mem->css outside of
mm/memcontrol.c (where we define struct mem_cgroup). There is one user
left (hwpoison_filter_task) after recent clean ups.
I think we shouldn't spread the usage inside the mm/memcontrol.c. The
compiler inlines the function for all callers added by this patch but I
wouldn't rely on it. It is also unfortunate that we cannot convert all
dereferences (e.g. const mem_cgroup).
Moreover it doesn't add any additional type safety. So I would vote for
not taking the patch but if others like it I will not block it.
> V2->V1:
> * restore the mistake modify in mem_cgroup_css
>
> Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
> ---
> mm/memcontrol.c | 89 ++++++++++++++++++++++++++++--------------------------
> 1 files changed, 46 insertions(+), 43 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f72b5e5..f27084c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -645,7 +645,7 @@ retry:
> */
> __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
> if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
> - !css_tryget(&mz->memcg->css))
> + !css_tryget(mem_cgroup_css(mz->memcg)))
> goto retry;
> done:
> return mz;
> @@ -899,7 +899,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
> memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
> if (unlikely(!memcg))
> break;
> - } while (!css_tryget(&memcg->css));
> + } while (!css_tryget(mem_cgroup_css(memcg)));
> rcu_read_unlock();
> return memcg;
> }
> @@ -935,10 +935,10 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
> root = root_mem_cgroup;
>
> if (prev && !reclaim)
> - id = css_id(&prev->css);
> + id = css_id(mem_cgroup_css(prev));
>
> if (prev && prev != root)
> - css_put(&prev->css);
> + css_put(mem_cgroup_css(prev));
>
> if (!root->use_hierarchy && root != root_mem_cgroup) {
> if (prev)
> @@ -963,9 +963,10 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
> }
>
> rcu_read_lock();
> - css = css_get_next(&mem_cgroup_subsys, id + 1, &root->css, &id);
> + css = css_get_next(&mem_cgroup_subsys, id + 1,
> + mem_cgroup_css(root), &id);
> if (css) {
> - if (css == &root->css || css_tryget(css))
> + if (css == mem_cgroup_css(root) || css_tryget(css))
> memcg = container_of(css,
> struct mem_cgroup, css);
> } else
> @@ -997,7 +998,7 @@ void mem_cgroup_iter_break(struct mem_cgroup *root,
> if (!root)
> root = root_mem_cgroup;
> if (prev && prev != root)
> - css_put(&prev->css);
> + css_put(mem_cgroup_css(prev));
> }
>
> /*
> @@ -1150,7 +1151,8 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> return true;
> if (!root_memcg->use_hierarchy || !memcg)
> return false;
> - return css_is_ancestor(&memcg->css, &root_memcg->css);
> + return css_is_ancestor(mem_cgroup_css(memcg),
> + &root_memcg->css);
> }
>
> static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> @@ -1183,7 +1185,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
> task_lock(task);
> curr = mem_cgroup_from_task(task);
> if (curr)
> - css_get(&curr->css);
> + css_get(mem_cgroup_css(curr));
> task_unlock(task);
> }
> if (!curr)
> @@ -1195,7 +1197,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
> * hierarchy(even if use_hierarchy is disabled in "memcg").
> */
> ret = mem_cgroup_same_or_subtree(memcg, curr);
> - css_put(&curr->css);
> + css_put(mem_cgroup_css(curr));
> return ret;
> }
>
> @@ -1251,7 +1253,7 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
>
> int mem_cgroup_swappiness(struct mem_cgroup *memcg)
> {
> - struct cgroup *cgrp = memcg->css.cgroup;
> + struct cgroup *cgrp = mem_cgroup_css(memcg)->cgroup;
>
> /* root ? */
> if (cgrp->parent == NULL)
> @@ -1396,7 +1398,7 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
>
> rcu_read_lock();
>
> - mem_cgrp = memcg->css.cgroup;
> + mem_cgrp = mem_cgroup_css(memcg)->cgroup;
> task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);
>
> ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
> @@ -2275,12 +2277,12 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
> again:
> if (*ptr) { /* css should be a valid one */
> memcg = *ptr;
> - VM_BUG_ON(css_is_removed(&memcg->css));
> + VM_BUG_ON(css_is_removed(mem_cgroup_css(memcg)));
> if (mem_cgroup_is_root(memcg))
> goto done;
> if (nr_pages == 1 && consume_stock(memcg))
> goto done;
> - css_get(&memcg->css);
> + css_get(mem_cgroup_css(memcg));
> } else {
> struct task_struct *p;
>
> @@ -2316,7 +2318,7 @@ again:
> goto done;
> }
> /* after here, we may be blocked. we need to get refcnt */
> - if (!css_tryget(&memcg->css)) {
> + if (!css_tryget(mem_cgroup_css(memcg))) {
> rcu_read_unlock();
> goto again;
> }
> @@ -2328,7 +2330,7 @@ again:
>
> /* If killed, bypass charge */
> if (fatal_signal_pending(current)) {
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> goto bypass;
> }
>
> @@ -2344,29 +2346,29 @@ again:
> break;
> case CHARGE_RETRY: /* not in OOM situation but retry */
> batch = nr_pages;
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> memcg = NULL;
> goto again;
> case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> goto nomem;
> case CHARGE_NOMEM: /* OOM routine works */
> if (!oom) {
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> goto nomem;
> }
> /* If oom, we never return -ENOMEM */
> nr_oom_retries--;
> break;
> case CHARGE_OOM_DIE: /* Killed by OOM Killer */
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> goto bypass;
> }
> } while (ret != CHARGE_OK);
>
> if (batch > nr_pages)
> refill_stock(memcg, batch - nr_pages);
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> done:
> *ptr = memcg;
> return 0;
> @@ -2445,14 +2447,14 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> lock_page_cgroup(pc);
> if (PageCgroupUsed(pc)) {
> memcg = pc->mem_cgroup;
> - if (memcg && !css_tryget(&memcg->css))
> + if (memcg && !css_tryget(mem_cgroup_css(memcg)))
> memcg = NULL;
> } else if (PageSwapCache(page)) {
> ent.val = page_private(page);
> id = lookup_swap_cgroup_id(ent);
> rcu_read_lock();
> memcg = mem_cgroup_lookup(id);
> - if (memcg && !css_tryget(&memcg->css))
> + if (memcg && !css_tryget(mem_cgroup_css(memcg)))
> memcg = NULL;
> rcu_read_unlock();
> }
> @@ -2795,7 +2797,7 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
> goto charge_cur_mm;
> *memcgp = memcg;
> ret = __mem_cgroup_try_charge(NULL, mask, 1, memcgp, true);
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> if (ret == -EINTR)
> ret = 0;
> return ret;
> @@ -2816,7 +2818,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
> return;
> if (!memcg)
> return;
> - cgroup_exclude_rmdir(&memcg->css);
> + cgroup_exclude_rmdir(mem_cgroup_css(memcg));
>
> __mem_cgroup_commit_charge(memcg, page, 1, ctype, true);
> /*
> @@ -2835,7 +2837,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
> * So, rmdir()->pre_destroy() can be called while we do this charge.
> * In that case, we need to call pre_destroy() again. check it here.
> */
> - cgroup_release_and_wakeup_rmdir(&memcg->css);
> + cgroup_release_and_wakeup_rmdir(mem_cgroup_css(memcg));
> }
>
> void mem_cgroup_commit_charge_swapin(struct page *page,
> @@ -3083,7 +3085,7 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
> * mem_cgroup_get() was called in uncharge().
> */
> if (do_swap_account && swapout && memcg)
> - swap_cgroup_record(ent, css_id(&memcg->css));
> + swap_cgroup_record(ent, css_id(mem_cgroup_css(memcg)));
> }
> #endif
>
> @@ -3135,8 +3137,8 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry,
> {
> unsigned short old_id, new_id;
>
> - old_id = css_id(&from->css);
> - new_id = css_id(&to->css);
> + old_id = css_id(mem_cgroup_css(from));
> + new_id = css_id(mem_cgroup_css(to));
>
> if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
> mem_cgroup_swap_statistics(from, false);
> @@ -3184,7 +3186,7 @@ int mem_cgroup_prepare_migration(struct page *page,
> lock_page_cgroup(pc);
> if (PageCgroupUsed(pc)) {
> memcg = pc->mem_cgroup;
> - css_get(&memcg->css);
> + css_get(mem_cgroup_css(memcg));
> /*
> * At migrating an anonymous page, its mapcount goes down
> * to 0 and uncharge() will be called. But, even if it's fully
> @@ -3227,7 +3229,7 @@ int mem_cgroup_prepare_migration(struct page *page,
>
> *memcgp = memcg;
> ret = __mem_cgroup_try_charge(NULL, gfp_mask, 1, memcgp, false);
> - css_put(&memcg->css);/* drop extra refcnt */
> + css_put(mem_cgroup_css(memcg));/* drop extra refcnt */
> if (ret) {
> if (PageAnon(page)) {
> lock_page_cgroup(pc);
> @@ -3268,7 +3270,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
> if (!memcg)
> return;
> /* blocks rmdir() */
> - cgroup_exclude_rmdir(&memcg->css);
> + cgroup_exclude_rmdir(mem_cgroup_css(memcg));
> if (!migration_ok) {
> used = oldpage;
> unused = newpage;
> @@ -3306,7 +3308,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
> * So, rmdir()->pre_destroy() can be called while we do this charge.
> * In that case, we need to call pre_destroy() again. check it here.
> */
> - cgroup_release_and_wakeup_rmdir(&memcg->css);
> + cgroup_release_and_wakeup_rmdir(mem_cgroup_css(memcg));
> }
>
> /*
> @@ -3575,7 +3577,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> next_mz =
> __mem_cgroup_largest_soft_limit_node(mctz);
> if (next_mz == mz)
> - css_put(&next_mz->memcg->css);
> + css_put(mem_cgroup_css(next_mz->memcg));
> else /* next_mz == NULL or other memcg */
> break;
> } while (1);
> @@ -3593,7 +3595,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> /* If excess == 0, no tree ops */
> __mem_cgroup_insert_exceeded(mz->memcg, mz, mctz, excess);
> spin_unlock(&mctz->lock);
> - css_put(&mz->memcg->css);
> + css_put(mem_cgroup_css(mz->memcg));
> loop++;
> /*
> * Could not reclaim anything and there are no more
> @@ -3606,7 +3608,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> break;
> } while (!nr_reclaimed);
> if (next_mz)
> - css_put(&next_mz->memcg->css);
> + css_put(mem_cgroup_css(next_mz->memcg));
> return nr_reclaimed;
> }
>
> @@ -3679,9 +3681,9 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all)
> int ret;
> int node, zid, shrink;
> int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> - struct cgroup *cgrp = memcg->css.cgroup;
> + struct cgroup *cgrp = mem_cgroup_css(memcg)->cgroup;
>
> - css_get(&memcg->css);
> + css_get(mem_cgroup_css(memcg));
>
> shrink = 0;
> /* should free all ? */
> @@ -3722,7 +3724,7 @@ move_account:
> /* "ret" should also be checked to ensure all lists are empty. */
> } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0 || ret);
> out:
> - css_put(&memcg->css);
> + css_put(mem_cgroup_css(memcg));
> return ret;
>
> try_to_free:
> @@ -3933,7 +3935,7 @@ static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
>
> min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
> min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
> - cgroup = memcg->css.cgroup;
> + cgroup = mem_cgroup_css(memcg)->cgroup;
> if (!memcg->use_hierarchy)
> goto out;
>
> @@ -4770,7 +4772,7 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
> int node;
>
> mem_cgroup_remove_from_trees(memcg);
> - free_css_id(&mem_cgroup_subsys, &memcg->css);
> + free_css_id(&mem_cgroup_subsys, mem_cgroup_css(memcg));
>
> for_each_node(node)
> free_mem_cgroup_per_zone_info(memcg, node);
> @@ -4926,7 +4928,7 @@ mem_cgroup_create(struct cgroup *cont)
> mem_cgroup_put(memcg);
> return ERR_PTR(error);
> }
> - return &memcg->css;
> + return mem_cgroup_css(memcg);
> free_out:
> __mem_cgroup_free(memcg);
> return ERR_PTR(error);
> @@ -5145,7 +5147,8 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
> }
> /* There is a swap entry and a page doesn't exist or isn't charged */
> if (ent.val && !ret &&
> - css_id(&mc.from->css) == lookup_swap_cgroup_id(ent)) {
> + css_id(mem_cgroup_css(mc.from)) ==
> + lookup_swap_cgroup_id(ent)) {
> ret = MC_TARGET_SWAP;
> if (target)
> target->ent = ent;
> --
> 1.7.7.6
>
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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