mm: check the return value of lookup_page_ext for all call sites

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

[akpm@linux-foundation.org: fix build-breaking typos]
[arnd@arndb.de: fix build problems from lookup_page_ext]
  Link: http://lkml.kernel.org/r/6285269.2CksypHdYp@wuerfel
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1464023768-31025-1-git-send-email-yang.shi@linaro.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 41 insertions, 1 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f8f3bfc435ee..d27e8b968ac3 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 792b56da13d8..c6cda3e36212 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 +64,7 @@ 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);
+
         struct stack_trace trace = {
                 .nr_entries = 0,
                 .max_entries = ARRAY_SIZE(page_ext->trace_entries),
@@ -69,6 +72,9 @@ void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
                 .skip = 3,
         };
 
+        if (unlikely(!page_ext))
+                return;
+
         save_stack_trace(&trace);
 
         page_ext->order = order;
@@ -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;
 }
@@ -99,6 +113,9 @@ void __copy_page_owner(struct page *oldpage, struct page *newpage)
         struct page_ext *new_ext = lookup_page_ext(newpage);
         int i;
 
+        if (unlikely(!old_ext || !new_ext))
+                return;
+
         new_ext->order = old_ext->order;
         new_ext->gfp_mask = old_ext->gfp_mask;
         new_ext->nr_entries = old_ext->nr_entries;
@@ -193,6 +210,11 @@ void __dump_page_owner(struct page *page)
         gfp_t gfp_mask = page_ext->gfp_mask;
         int mt = gfpflags_to_migratetype(gfp_mask);
 
+        if (unlikely(!page_ext)) {
+                pr_alert("There is not page extension available.\n");
+                return;
+        }
+
         if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
                 pr_alert("page_owner info is not active (free page?)\n");
                 return;
@@ -251,6 +273,8 @@ 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 +341,8 @@ 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 1eae5fad2446..2e647c65916b 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 77e42ef388c2..cb2a67bb4158 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;