linux-kernel - [PATCH v3] mm/page_alloc: add a helper function to check page before alloc/free

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Message-Id: <1440679917-3507-1-git-send-email-bywxiaobai@163.com>
Date:	Thu, 27 Aug 2015 20:51:57 +0800
From:	Yaowei Bai <bywxiaobai@....com>
To:	akpm@...ux-foundation.org, mgorman@...e.de, vbabka@...e.cz,
	mhocko@...nel.org, js1304@...il.com, hannes@...xchg.org,
	alexander.h.duyck@...hat.com, sasha.levin@...cle.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] mm/page_alloc: add a helper function to check page before alloc/free

The major portion of check_new_page() and free_pages_check() are same,
introduce a helper function check_one_page() for simplification.

Change in v3:
	- add the missed __PG_HWPOISON check per Michal Hocko
Change in v2:
	- use bad_flags as parameter directly per Michal Hocko

Signed-off-by: Yaowei Bai <bywxiaobai@....com>
---
 mm/page_alloc.c | 54 +++++++++++++++++++++++-------------------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b5240b..0c9c82a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -707,10 +707,9 @@ out:
 	zone->free_area[order].nr_free++;
 }
 
-static inline int free_pages_check(struct page *page)
+static inline int check_one_page(struct page *page, unsigned long bad_flags)
 {
 	const char *bad_reason = NULL;
-	unsigned long bad_flags = 0;
 
 	if (unlikely(page_mapcount(page)))
 		bad_reason = "nonzero mapcount";
@@ -718,9 +717,16 @@ static inline int free_pages_check(struct page *page)
 		bad_reason = "non-NULL mapping";
 	if (unlikely(atomic_read(&page->_count) != 0))
 		bad_reason = "nonzero _count";
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
-		bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
-		bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
+	if (bad_flags == PAGE_FLAGS_CHECK_AT_PREP) {
+		if (unlikely(page->flags & bad_flags))
+			bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
+		if (unlikely(page->flags & __PG_HWPOISON)) {
+			bad_reason = "HWPoisoned (hardware-corrupted)";
+			bad_flags = __PG_HWPOISON;
+		}
+	} else if (bad_flags == PAGE_FLAGS_CHECK_AT_FREE) {
+		if (unlikely(page->flags & bad_flags))
+			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag set";
 	}
 #ifdef CONFIG_MEMCG
 	if (unlikely(page->mem_cgroup))
@@ -730,6 +736,17 @@ static inline int free_pages_check(struct page *page)
 		bad_page(page, bad_reason, bad_flags);
 		return 1;
 	}
+	return 0;
+}
+
+static inline int free_pages_check(struct page *page)
+{
+	int ret = 0;
+
+	ret = check_one_page(page, PAGE_FLAGS_CHECK_AT_FREE);
+	if (ret)
+		return ret;
+
 	page_cpupid_reset_last(page);
 	if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
 		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
@@ -1287,32 +1304,7 @@ static inline void expand(struct zone *zone, struct page *page,
  */
 static inline int check_new_page(struct page *page)
 {
-	const char *bad_reason = NULL;
-	unsigned long bad_flags = 0;
-
-	if (unlikely(page_mapcount(page)))
-		bad_reason = "nonzero mapcount";
-	if (unlikely(page->mapping != NULL))
-		bad_reason = "non-NULL mapping";
-	if (unlikely(atomic_read(&page->_count) != 0))
-		bad_reason = "nonzero _count";
-	if (unlikely(page->flags & __PG_HWPOISON)) {
-		bad_reason = "HWPoisoned (hardware-corrupted)";
-		bad_flags = __PG_HWPOISON;
-	}
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
-		bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
-		bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
-	}
-#ifdef CONFIG_MEMCG
-	if (unlikely(page->mem_cgroup))
-		bad_reason = "page still charged to cgroup";
-#endif
-	if (unlikely(bad_reason)) {
-		bad_page(page, bad_reason, bad_flags);
-		return 1;
-	}
-	return 0;
+	return check_one_page(page, PAGE_FLAGS_CHECK_AT_PREP);
 }
 
 static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
-- 
1.9.1


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