On Mon, 7 Mar 2011 15:00:49 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > At this point, I'm not sure this is a fix for > https://bugzilla.kernel.org/show_bug.cgi?id=30432. > > The behavior seems very similar to SwapCache case and this is a possible > bug and this patch can be a fix. Nishimura-san, how do you think ? > As long as I can read the source code, I also think this is a possible bug. > But I'm not sure how to test this....please review. > > = > fs/fuse/dev.c::fuse_try_move_page() does > > (1) remove a page from page cache by ->steal() > (2) re-add the page to page cache > (3) link the page to LRU if it was _not_ on LRU at (1) > > > This implies the page can be _on_ LRU when add_to_page_cache_locked() is called. > So, the page is added to a memory cgroup while it's on LRU. > > This is the same behavior as SwapCache, 'newly charged pages may be on LRU' > and needs special care as > - remove page from old memcg's LRU before overwrite pc->mem_cgroup. > - add page to new memcg's LRU after overwrite pc->mem_cgroup. > > So, reusing SwapCache code with renaming for fix. > > Note: a page on pagevec(LRU). > > If a page is not PageLRU(page) but on pagevec(LRU), it may be added to LRU > while we overwrite page->mapping. But in that case, PCG_USED bit of > the page_cgroup is not set and the page_cgroup will not be added to > wrong memcg's LRU. So, this patch's logic will work fine. > (It has been tested with SwapCache.) > As for SwapCache, mem_cgroup_lru_add_after_commit() will be allways called, and it will link the page to LRU. But, if I read this patch correctly, a page cache on pagevec may not be added to a *proper* memcg's LRU. lru_add_drain() mem_cgroup_cache_charge() ---------------------------------------------------------- if (!PageLRU()) SetPageLRU() add_page_to_lru_list() mem_cgroup_add_lru_list() -> do nothing mem_cgroup_charge_common() mem_cgroup_commit_charge() -> set PCG_USED Right ? Thanks, Daisuke Nishimura. > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > --- > mm/memcontrol.c | 42 +++++++++++++++++++++++------------------- > 1 file changed, 23 insertions(+), 19 deletions(-) > > Index: mmotm-0303/mm/memcontrol.c > =================================================================== > --- mmotm-0303.orig/mm/memcontrol.c > +++ mmotm-0303/mm/memcontrol.c > @@ -926,13 +926,12 @@ void mem_cgroup_add_lru_list(struct page > } > > /* > - * At handling SwapCache, pc->mem_cgroup may be changed while it's linked to > - * lru because the page may.be reused after it's fully uncharged (because of > - * SwapCache behavior).To handle that, unlink page_cgroup from LRU when charge > - * it again. This function is only used to charge SwapCache. It's done under > - * lock_page and expected that zone->lru_lock is never held. > + * At handling SwapCache and other FUSE stuff, pc->mem_cgroup may be changed > + * while it's linked to lru because the page may be reused after it's fully > + * uncharged. To handle that, unlink page_cgroup from LRU when charge it again. > + * It's done under lock_page and expected that zone->lru_lock isnever held. > */ > -static void mem_cgroup_lru_del_before_commit_swapcache(struct page *page) > +static void mem_cgroup_lru_del_before_commit(struct page *page) > { > unsigned long flags; > struct zone *zone = page_zone(page); > @@ -948,7 +947,7 @@ static void mem_cgroup_lru_del_before_co > spin_unlock_irqrestore(&zone->lru_lock, flags); > } > > -static void mem_cgroup_lru_add_after_commit_swapcache(struct page *page) > +static void mem_cgroup_lru_add_after_commit(struct page *page) > { > unsigned long flags; > struct zone *zone = page_zone(page); > @@ -2428,7 +2427,7 @@ int mem_cgroup_newpage_charge(struct pag > } > > static void > -__mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr, > +__mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *ptr, > enum charge_type ctype); > > int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm, > @@ -2468,17 +2467,22 @@ int mem_cgroup_cache_charge(struct page > if (unlikely(!mm)) > mm = &init_mm; > > - if (page_is_file_cache(page)) > - return mem_cgroup_charge_common(page, mm, gfp_mask, > + if (page_is_file_cache(page) && !PageLRU(page)) { > + ret = mem_cgroup_charge_common(page, mm, gfp_mask, > MEM_CGROUP_CHARGE_TYPE_CACHE); > - > - /* shmem */ > - if (PageSwapCache(page)) { > + } else if (page_is_file_cache(page)) { > + struct mem_cgroup *mem; > + /* Page on LRU should be moved to the _new_ LRU */ > + ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &mem, true); > + if (!ret) > + __mem_cgroup_commit_charge_lrucare(page, mem, > + MEM_CGROUP_CHARGE_TYPE_CACHE); > + } else if (PageSwapCache(page)) { > struct mem_cgroup *mem; > - > ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem); > + > if (!ret) > - __mem_cgroup_commit_charge_swapin(page, mem, > + __mem_cgroup_commit_charge_lrucare(page, mem, > MEM_CGROUP_CHARGE_TYPE_SHMEM); > } else > ret = mem_cgroup_charge_common(page, mm, gfp_mask, > @@ -2529,7 +2533,7 @@ charge_cur_mm: > } > > static void > -__mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr, > +__mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *ptr, > enum charge_type ctype) > { > struct page_cgroup *pc; > @@ -2540,9 +2544,9 @@ __mem_cgroup_commit_charge_swapin(struct > return; > cgroup_exclude_rmdir(&ptr->css); > pc = lookup_page_cgroup(page); > - mem_cgroup_lru_del_before_commit_swapcache(page); > + mem_cgroup_lru_del_before_commit(page); > __mem_cgroup_commit_charge(ptr, page, 1, pc, ctype); > - mem_cgroup_lru_add_after_commit_swapcache(page); > + mem_cgroup_lru_add_after_commit(page); > /* > * Now swap is on-memory. This means this page may be > * counted both as mem and swap....double count. > @@ -2580,7 +2584,7 @@ __mem_cgroup_commit_charge_swapin(struct > > void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) > { > - __mem_cgroup_commit_charge_swapin(page, ptr, > + __mem_cgroup_commit_charge_lrucare(page, ptr, > MEM_CGROUP_CHARGE_TYPE_MAPPED); > } > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>