linux-kernel - [PATCH 2/6] mm/debug: Factor PagePoisoned out of __dump

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Date:   Sat, 17 Apr 2021 00:15:27 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/6] mm/debug: Factor PagePoisoned out of __dump_page

Move the PagePoisoned test into dump_page().  Skip the hex print
for poisoned pages -- we know they're full of ffffffff.  Move the
reason printing from __dump_page() to dump_page().

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/debug.c | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/mm/debug.c b/mm/debug.c
index 84cdcd0f7bd3..e73fe0a8ec3d 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -42,11 +42,10 @@ const struct trace_print_flags vmaflag_names[] = {
 	{0, NULL}
 };
 
-static void __dump_page(struct page *page, const char *reason)
+static void __dump_page(struct page *page)
 {
 	struct page *head = compound_head(page);
 	struct address_space *mapping;
-	bool page_poisoned = PagePoisoned(page);
 	bool compound = PageCompound(page);
 	/*
 	 * Accessing the pageblock without the zone lock. It could change to
@@ -58,16 +57,6 @@ static void __dump_page(struct page *page, const char *reason)
 	int mapcount;
 	char *type = "";
 
-	/*
-	 * If struct page is poisoned don't access Page*() functions as that
-	 * leads to recursive loop. Page*() check for poisoned pages, and calls
-	 * dump_page() when detected.
-	 */
-	if (page_poisoned) {
-		pr_warn("page:%px is uninitialized and poisoned", page);
-		goto hex_only;
-	}
-
 	if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
 		/*
 		 * Corrupt page, so we cannot call page_mapping. Instead, do a
@@ -173,8 +162,6 @@ static void __dump_page(struct page *page, const char *reason)
 
 	pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
 		page_cma ? " CMA" : "");
-
-hex_only:
 	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
 			sizeof(unsigned long), page,
 			sizeof(struct page), false);
@@ -182,14 +169,16 @@ static void __dump_page(struct page *page, const char *reason)
 		print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32,
 			sizeof(unsigned long), head,
 			sizeof(struct page), false);
-
-	if (reason)
-		pr_warn("page dumped because: %s\n", reason);
 }
 
 void dump_page(struct page *page, const char *reason)
 {
-	__dump_page(page, reason);
+	if (PagePoisoned(page))
+		pr_warn("page:%p is uninitialized and poisoned", page);
+	else
+		__dump_page(page);
+	if (reason)
+		pr_warn("page dumped because: %s\n", reason);
 	dump_page_owner(page);
 }
 EXPORT_SYMBOL(dump_page);
-- 
2.30.2