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@xxxxxxxxxx> > --- > 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; > -- There is another race with here. init_section_page_ext < reordering > section->page_ext = base - pfn lookup_page_ext if (section->page_ext) section->page_ext + pfn base = alloc_page_ext I guess alloc_page_ext doesn't make sure to prevent such reordering so caller of memory allocating APIB should provide right memory barrier. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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