mm/page_owner: fix recursion bug after changing skip entries

This patch fixes commit 5f48f0bd4e36 ("mm, page_owner: skip unnecessary
stack_trace entries").

Because if we skip first two entries then logic of checking count value
as 2 for recursion is broken and code will go in one depth recursion.

so we need to check only one call of _RET_IP(__set_page_owner) while
checking for recursion.

Current Backtrace while checking for recursion:-

  (save_stack)             from (__set_page_owner)  // (But recursion returns true here)
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)       // recursion should return true here
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask+)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)

Correct Backtrace with fix:

  (save_stack)             from (__set_page_owner) // recursion returned true here
  (__set_page_owner)       from (get_page_from_freelist)
  (get_page_from_freelist) from (__alloc_pages_nodemask+)
  (__alloc_pages_nodemask) from (depot_save_stack)
  (depot_save_stack)       from (save_stack)
  (save_stack)             from (__set_page_owner)
  (__set_page_owner)       from (get_page_from_freelist)

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 5f48f0bd4e36 ("mm, page_owner: skip unnecessary stack_trace entries")
Signed-off-by: Maninder Singh <[email protected]>
Signed-off-by: Vaneet Narang <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Ayush Mittal <[email protected]>
Cc: Prakash Gupta <[email protected]>
Cc: Vinayak Menon <[email protected]>
Cc: Vasyl Gomonovych <[email protected]>
Cc: Amit Sahrawat <[email protected]>
Cc: <[email protected]>
Cc: Vaneet Narang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 3 insertions, 3 deletions

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 9886c6073828..7172e0a80e13 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -123,13 +123,13 @@ void __reset_page_owner(struct page *page, unsigned int order)
 static inline bool check_recursive_alloc(struct stack_trace *trace,
 					unsigned long ip)
 {
-	int i, count;
+	int i;
 
 	if (!trace->nr_entries)
 		return false;
 
-	for (i = 0, count = 0; i < trace->nr_entries; i++) {
-		if (trace->entries[i] == ip && ++count == 2)
+	for (i = 0; i < trace->nr_entries; i++) {
+		if (trace->entries[i] == ip)
 			return true;
 	}