linux-kernel - [Patch v3 2/5] mm/page_alloc.c: bad_flags is not necessary for bad

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Message-Id: <20200411220357.9636-3-richard.weiyang@gmail.com>
Date:   Sat, 11 Apr 2020 22:03:54 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        rientjes@...gle.com, anshuman.khandual@....com, david@...hat.com,
        Wei Yang <richard.weiyang@...il.com>
Subject: [Patch v3 2/5] mm/page_alloc.c: bad_flags is not necessary for bad_page()

After commit 5b57b8f22709 ("mm/debug.c: always print flags in
dump_page()"), page->flags is always printed for a bad page. It is not
necessary to have bad_flags any more.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
Suggested-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/page_alloc.c | 34 ++++++++++------------------------
 1 file changed, 10 insertions(+), 24 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7327dc039069..0648127af872 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -602,8 +602,7 @@ static inline int __maybe_unused bad_range(struct zone *zone, struct page *page)
 }
 #endif
 
-static void bad_page(struct page *page, const char *reason,
-		unsigned long bad_flags)
+static void bad_page(struct page *page, const char *reason)
 {
 	static unsigned long resume;
 	static unsigned long nr_shown;
@@ -632,10 +631,6 @@ static void bad_page(struct page *page, const char *reason,
 	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
 	__dump_page(page, reason);
-	bad_flags &= page->flags;
-	if (bad_flags)
-		pr_alert("bad because of flags: %#lx(%pGp)\n",
-						bad_flags, &bad_flags);
 	dump_page_owner(page);
 
 	print_modules();
@@ -1020,11 +1015,7 @@ static inline bool page_expected_state(struct page *page,
 
 static void free_pages_check_bad(struct page *page)
 {
-	const char *bad_reason;
-	unsigned long bad_flags;
-
-	bad_reason = NULL;
-	bad_flags = 0;
+	const char *bad_reason = NULL;
 
 	if (unlikely(atomic_read(&page->_mapcount) != -1))
 		bad_reason = "nonzero mapcount";
@@ -1032,15 +1023,13 @@ static void free_pages_check_bad(struct page *page)
 		bad_reason = "non-NULL mapping";
 	if (unlikely(page_ref_count(page) != 0))
 		bad_reason = "nonzero _refcount";
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
+	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;
-	}
 #ifdef CONFIG_MEMCG
 	if (unlikely(page->mem_cgroup))
 		bad_reason = "page still charged to cgroup";
 #endif
-	bad_page(page, bad_reason, bad_flags);
+	bad_page(page, bad_reason);
 }
 
 static inline int free_pages_check(struct page *page)
@@ -1071,7 +1060,7 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
 	case 1:
 		/* the first tail page: ->mapping may be compound_mapcount() */
 		if (unlikely(compound_mapcount(page))) {
-			bad_page(page, "nonzero compound_mapcount", 0);
+			bad_page(page, "nonzero compound_mapcount");
 			goto out;
 		}
 		break;
@@ -1083,17 +1072,17 @@ static int free_tail_pages_check(struct page *head_page, struct page *page)
 		break;
 	default:
 		if (page->mapping != TAIL_MAPPING) {
-			bad_page(page, "corrupted mapping in tail page", 0);
+			bad_page(page, "corrupted mapping in tail page");
 			goto out;
 		}
 		break;
 	}
 	if (unlikely(!PageTail(page))) {
-		bad_page(page, "PageTail not set", 0);
+		bad_page(page, "PageTail not set");
 		goto out;
 	}
 	if (unlikely(compound_head(page) != head_page)) {
-		bad_page(page, "compound_head not consistent", 0);
+		bad_page(page, "compound_head not consistent");
 		goto out;
 	}
 	ret = 0;
@@ -2035,7 +2024,6 @@ static inline void expand(struct zone *zone, struct page *page,
 static void check_new_page_bad(struct page *page)
 {
 	const char *bad_reason = NULL;
-	unsigned long bad_flags = 0;
 
 	if (unlikely(page->flags & __PG_HWPOISON)) {
 		/* Don't complain about hwpoisoned pages */
@@ -2048,15 +2036,13 @@ static void check_new_page_bad(struct page *page)
 		bad_reason = "non-NULL mapping";
 	if (unlikely(page_ref_count(page) != 0))
 		bad_reason = "nonzero _refcount";
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
+	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
-	bad_page(page, bad_reason, bad_flags);
+	bad_page(page, bad_reason);
 }
 
 /*
-- 
2.23.0