Messages in this thread | | | Subject | Re: [PATCH] mm: check the return value of lookup_page_ext for all call sites | From | "Shi, Yang" <> | Date | Thu, 26 May 2016 16:15:28 -0700 |
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On 5/25/2016 5:37 PM, Minchan Kim wrote: > On Tue, May 24, 2016 at 11:58:11AM +0900, Minchan Kim wrote: >> On Mon, May 23, 2016 at 10:16:08AM -0700, Yang Shi wrote: >>> Per the discussion with Joonsoo Kim [1], we need check the return value of >>> lookup_page_ext() for all call sites since it might return NULL in some cases, >>> although it is unlikely, i.e. memory hotplug. >>> >>> Tested with ltp with "page_owner=0". >>> >>> [1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE >>> >>> Signed-off-by: Yang Shi <yang.shi@linaro.org> >> >> I didn't read code code in detail to see how page_ext memory space >> allocated in boot code and memory hotplug but to me, it's not good >> to check NULL whenever we calls lookup_page_ext. >> >> More dangerous thing is now page_ext is used by optionable feature(ie, not >> critical for system stability) but if we want to use page_ext as >> another important tool for the system in future, >> it could be a serious problem. >> >> Can we put some hooks of page_ext into memory-hotplug so guarantee >> that page_ext memory space is allocated with memmap space at the >> same time? IOW, once every PFN wakers find a page is valid, page_ext >> is valid, too so lookup_page_ext never returns NULL on valid page >> by design. >> >> I hope we consider this direction, too. > > Yang, Could you think about this?
Thanks a lot for the suggestion. Sorry for the late reply, I was busy on preparing patches. I do agree this is a direction we should look into, but I haven't got time to think about it deeper. I hope Joonsoo could chime in too since he is the original author for page extension.
> > Even, your patch was broken, I think. > It doesn't work with !CONFIG_DEBUG_VM && !CONFIG_PAGE_POISONING because > lookup_page_ext doesn't return NULL in that case.
Actually, I think the #ifdef should be removed if lookup_page_ext() is possible to return NULL. It sounds not make sense returning NULL only when DEBUG_VM is enabled. It should return NULL no matter what debug config is selected. If Joonsoo agrees with me I'm going to come up with a patch to fix it.
Regards, Yang
> >> >> Thanks. >> >>> --- >>> include/linux/page_idle.h | 43 ++++++++++++++++++++++++++++++++++++------- >>> mm/page_alloc.c | 6 ++++++ >>> mm/page_owner.c | 27 +++++++++++++++++++++++++++ >>> mm/page_poison.c | 8 +++++++- >>> mm/vmstat.c | 2 ++ >>> 5 files changed, 78 insertions(+), 8 deletions(-) >>> >>> diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h >>> index bf268fa..8f5d4ad 100644 >>> --- a/include/linux/page_idle.h >>> +++ b/include/linux/page_idle.h >>> @@ -46,33 +46,62 @@ extern struct page_ext_operations page_idle_ops; >>> >>> static inline bool page_is_young(struct page *page) >>> { >>> - return test_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return false; >>> + >>> + return test_bit(PAGE_EXT_YOUNG, &page_ext->flags); >>> } >>> >>> static inline void set_page_young(struct page *page) >>> { >>> - set_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return; >>> + >>> + set_bit(PAGE_EXT_YOUNG, &page_ext->flags); >>> } >>> >>> static inline bool test_and_clear_page_young(struct page *page) >>> { >>> - return test_and_clear_bit(PAGE_EXT_YOUNG, >>> - &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return false; >>> + >>> + return test_and_clear_bit(PAGE_EXT_YOUNG, &page_ext->flags); >>> } >>> >>> static inline bool page_is_idle(struct page *page) >>> { >>> - return test_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return false; >>> + >>> + return test_bit(PAGE_EXT_IDLE, &page_ext->flags); >>> } >>> >>> static inline void set_page_idle(struct page *page) >>> { >>> - set_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return; >>> + >>> + set_bit(PAGE_EXT_IDLE, &page_ext->flags); >>> } >>> >>> static inline void clear_page_idle(struct page *page) >>> { >>> - clear_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); >>> + struct page_ext *page_ext; >>> + page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext) >>> + return; >>> + >>> + clear_bit(PAGE_EXT_IDLE, &page_ext->flags); >>> } >>> #endif /* CONFIG_64BIT */ >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index f8f3bfc..d27e8b9 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -656,6 +656,9 @@ static inline void set_page_guard(struct zone *zone, struct page *page, >>> return; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + return; >>> + >>> __set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags); >>> >>> INIT_LIST_HEAD(&page->lru); >>> @@ -673,6 +676,9 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, >>> return; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + return; >>> + >>> __clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags); >>> >>> set_page_private(page, 0); >>> diff --git a/mm/page_owner.c b/mm/page_owner.c >>> index 792b56d..902e398 100644 >>> --- a/mm/page_owner.c >>> +++ b/mm/page_owner.c >>> @@ -55,6 +55,8 @@ void __reset_page_owner(struct page *page, unsigned int order) >>> >>> for (i = 0; i < (1 << order); i++) { >>> page_ext = lookup_page_ext(page + i); >>> + if (unlikely(!page_ext)) >>> + continue; >>> __clear_bit(PAGE_EXT_OWNER, &page_ext->flags); >>> } >>> } >>> @@ -62,6 +64,10 @@ void __reset_page_owner(struct page *page, unsigned int order) >>> void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask) >>> { >>> struct page_ext *page_ext = lookup_page_ext(page); >>> + >>> + if (unlikely(!page_ext)) >>> + return; >>> + >>> struct stack_trace trace = { >>> .nr_entries = 0, >>> .max_entries = ARRAY_SIZE(page_ext->trace_entries), >>> @@ -82,6 +88,8 @@ void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask) >>> void __set_page_owner_migrate_reason(struct page *page, int reason) >>> { >>> struct page_ext *page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + return; >>> >>> page_ext->last_migrate_reason = reason; >>> } >>> @@ -89,6 +97,12 @@ void __set_page_owner_migrate_reason(struct page *page, int reason) >>> gfp_t __get_page_owner_gfp(struct page *page) >>> { >>> struct page_ext *page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + /* >>> + * The caller just returns 0 if no valid gfp >>> + * So return 0 here too. >>> + */ >>> + return 0; >>> >>> return page_ext->gfp_mask; >>> } >>> @@ -97,6 +111,10 @@ void __copy_page_owner(struct page *oldpage, struct page *newpage) >>> { >>> struct page_ext *old_ext = lookup_page_ext(oldpage); >>> struct page_ext *new_ext = lookup_page_ext(newpage); >>> + >>> + if (unlikely(!old_ext || !new_ext)) >>> + return; >>> + >>> int i; >>> >>> new_ext->order = old_ext->order; >>> @@ -186,6 +204,11 @@ err: >>> void __dump_page_owner(struct page *page) >>> { >>> struct page_ext *page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) { >>> + pr_alert("There is not page extension available.\n"); >>> + return; >>> + } >>> + >>> struct stack_trace trace = { >>> .nr_entries = page_ext->nr_entries, >>> .entries = &page_ext->trace_entries[0], >>> @@ -251,6 +274,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) >>> } >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + continue; >>> >>> /* >>> * Some pages could be missed by concurrent allocation or free, >>> @@ -317,6 +342,8 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone) >>> continue; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + continue; >>> >>> /* Maybe overraping zone */ >>> if (test_bit(PAGE_EXT_OWNER, &page_ext->flags)) >>> diff --git a/mm/page_poison.c b/mm/page_poison.c >>> index 1eae5fa..2e647c6 100644 >>> --- a/mm/page_poison.c >>> +++ b/mm/page_poison.c >>> @@ -54,6 +54,9 @@ static inline void set_page_poison(struct page *page) >>> struct page_ext *page_ext; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + return; >>> + >>> __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); >>> } >>> >>> @@ -62,6 +65,9 @@ static inline void clear_page_poison(struct page *page) >>> struct page_ext *page_ext; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + return; >>> + >>> __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); >>> } >>> >>> @@ -70,7 +76,7 @@ bool page_is_poisoned(struct page *page) >>> struct page_ext *page_ext; >>> >>> page_ext = lookup_page_ext(page); >>> - if (!page_ext) >>> + if (unlikely(!page_ext)) >>> return false; >>> >>> return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); >>> diff --git a/mm/vmstat.c b/mm/vmstat.c >>> index 77e42ef..cb2a67b 100644 >>> --- a/mm/vmstat.c >>> +++ b/mm/vmstat.c >>> @@ -1061,6 +1061,8 @@ static void pagetypeinfo_showmixedcount_print(struct seq_file *m, >>> continue; >>> >>> page_ext = lookup_page_ext(page); >>> + if (unlikely(!page_ext)) >>> + continue; >>> >>> if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) >>> continue; >>> -- >>> 2.0.2 >>> >>> -- >>> To unsubscribe, send a message with 'unsubscribe linux-mm' in >>> the body to majordomo@kvack.org. For more info on Linux MM, >>> see: http://www.linux-mm.org/ . >>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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