Messages in this thread | | | Date | Tue, 4 Nov 2008 18:04:29 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][PATCH 2/5] memcg : handle swap cache |
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On Tue, 4 Nov 2008 17:42:01 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> > +#ifdef CONFIG_SWAP > > +int mem_cgroup_cache_charge_swapin(struct page *page, > > + struct mm_struct *mm, gfp_t mask) > > +{ > > + int ret = 0; > > + > > + if (mem_cgroup_subsys.disabled) > > + return 0; > > + if (unlikely(!mm)) > > + mm = &init_mm; > > + > > + ret = mem_cgroup_charge_common(page, mm, mask, > > + MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL); > > + /* > > + * The page may be dropped from SwapCache because we don't have > > + * lock_page().This may cause charge-after-uncharge trouble. > > + * Fix it up here. (the caller have refcnt to this page and > > + * page itself is guaranteed not to be freed.) > > + */ > > + if (ret && !PageSwapCache(page)) > > + mem_cgroup_uncharge_swapcache(page); > > + > Hmm.. after [5/5], mem_cgroup_cache_charge_swapin has 'locked' parameter, > calls lock_page(if !locked), and checks PageSwapCache under page lock. > > Why not doing it in this patch? >
My intention is to guard swap_cgroup by lock_page() against SwapCache. In Mem+Swap controller. we get "memcg" from information in page->private. I think we need lock_page(), there.
But here, we don't refer page->private information. I think we don't need lock_page() because there is no inofrmation we depends on.
Thanks, -Kame
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