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
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;} @@ -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.