[PATCH] mm: add stackdepot information on page->private for tracking

["zhaoyang.huang" <zhaoyang.huang@unisoc.com>]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Private is vacant for most of Non-LRU pages while the user has explicitly
operation on page->private via set_page_private, I would like introduce
stackdepot information on page->private for a simplified tracking mechanism
which could be help for kernel driver's memory leak.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 mm/page_alloc.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e5486d4..b79a503 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -75,6 +75,7 @@
 #include <linux/khugepaged.h>
 #include <linux/buffer_head.h>
 #include <linux/delayacct.h>
+#include <linux/stackdepot.h>
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -2464,6 +2465,25 @@ static inline bool should_skip_init(gfp_t flags)
 	return (flags & __GFP_SKIP_ZERO);
 }
 
+#ifdef CONFIG_STACKDEPOT
+static noinline depot_stack_handle_t set_track_prepare(void)
+{
+       depot_stack_handle_t trace_handle;
+       unsigned long entries[16];
+       unsigned int nr_entries;
+
+       nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
+       trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
+
+       return trace_handle;
+}
+#else
+static inline depot_stack_handle_t set_track_prepare(void)
+{
+       return 0;
+}
+#endif
+
 inline void post_alloc_hook(struct page *page, unsigned int order,
 				gfp_t gfp_flags)
 {
@@ -2471,8 +2491,14 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 			!should_skip_init(gfp_flags);
 	bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
 	int i;
+	depot_stack_handle_t stack_handle = set_track_prepare();
 
-	set_page_private(page, 0);
+	/*
+	 * Don't worry, user will cover private directly without checking
+	 * this field and has ability to trace the page. This also will not
+	 * affect expected state when freeing
+	 */
+	set_page_private(page, stack_handle);
 	set_page_refcounted(page);
 
 	arch_alloc_page(page, order);
-- 
1.9.1