Re: [patch] mm: memcg: move pc lookup point to commit_charge()

Johannes Weiner
2012-04-24T19:38:58Z

Sorry, git-send-email didn't pick up the CCs, full quote here:

On Tue, Apr 24, 2012 at 09:31:00PM +0200, Johannes Weiner wrote:
> None of the callsites actually need the page_cgroup descriptor
> themselves, so just pass the page and do the look up in there.
>
> We already had two bugs (6568d4a 'mm: memcg: update the correct soft
> limit tree during migration' and 'memcg: fix Bad page state after
> replace_page_cache') where the passed page and pc were not referring
> to the same page frame.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: Hugh Dickins <hughd@google.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Michal Hocko <mhocko@suse.cz>
> ---
> mm/memcontrol.c | 17 +++++------------
> 1 files changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 884e936..1a28dd8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2461,10 +2461,10 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
> static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
> struct page *page,
> unsigned int nr_pages,
> - struct page_cgroup *pc,
> enum charge_type ctype,
> bool lrucare)
> {
> + struct page_cgroup *pc = lookup_page_cgroup(page);
> struct zone *uninitialized_var(zone);
> bool was_on_lru = false;
> bool anon;
> @@ -2701,7 +2701,6 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
> {
> struct mem_cgroup *memcg = NULL;
> unsigned int nr_pages = 1;
> - struct page_cgroup *pc;
> bool oom = true;
> int ret;
>
> @@ -2715,11 +2714,10 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
> oom = false;
> }
>
> - pc = lookup_page_cgroup(page);
> ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom);
> if (ret == -ENOMEM)
> return ret;
> - __mem_cgroup_commit_charge(memcg, page, nr_pages, pc, ctype, false);
> + __mem_cgroup_commit_charge(memcg, page, nr_pages, ctype, false);
> return 0;
> }
>
> @@ -2816,16 +2814,13 @@ static void
> __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
> enum charge_type ctype)
> {
> - struct page_cgroup *pc;
> -
> if (mem_cgroup_disabled())
> return;
> if (!memcg)
> return;
> cgroup_exclude_rmdir(&memcg->css);
>
> - pc = lookup_page_cgroup(page);
> - __mem_cgroup_commit_charge(memcg, page, 1, pc, ctype, true);
> + __mem_cgroup_commit_charge(memcg, page, 1, ctype, true);
> /*
> * Now swap is on-memory. This means this page may be
> * counted both as mem and swap....double count.
> @@ -3254,14 +3249,13 @@ int mem_cgroup_prepare_migration(struct page *page,
> * page. In the case new page is migrated but not remapped, new page's
> * mapcount will be finally 0 and we call uncharge in end_migration().
> */
> - pc = lookup_page_cgroup(newpage);
> if (PageAnon(page))
> ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
> else if (page_is_file_cache(page))
> ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
> else
> ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
> - __mem_cgroup_commit_charge(memcg, newpage, 1, pc, ctype, false);
> + __mem_cgroup_commit_charge(memcg, newpage, 1, ctype, false);
> return ret;
> }
>
> @@ -3348,8 +3342,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
> * the newpage may be on LRU(or pagevec for LRU) already. We lock
> * LRU while we overwrite pc->mem_cgroup.
> */
> - pc = lookup_page_cgroup(newpage);
> - __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true);
> + __mem_cgroup_commit_charge(memcg, newpage, 1, type, true);
> }
>
> #ifdef CONFIG_DEBUG_VM
> --
> 1.7.7.6
>
> --
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