linux-kernel - [RFC PATCH v2 16/30] mm: debug: adapt dump

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Date:   Mon, 28 Sep 2020 13:54:14 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     linux-mm@...ck.org
Cc:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Roman Gushchin <guro@...com>, Rik van Riel <riel@...riel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        David Hildenbrand <david@...hat.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Nellans <dnellans@...dia.com>,
        linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>
Subject: [RFC PATCH v2 16/30] mm: debug: adapt dump_page to PUD THP.

From: Zi Yan <ziy@...dia.com>

Since the order of a PUD THP is greater than MAX_ORDER, do not consider
its tail pages corrupted. Also print sub_compound_mapcount when dumping
a PMDPageInPUD.

Signed-off-by: Zi Yan <ziy@...dia.com>
---
 mm/debug.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/debug.c b/mm/debug.c
index ccca576b2899..f5b035dc620d 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -68,7 +68,9 @@ void __dump_page(struct page *page, const char *reason)
 		goto hex_only;
 	}
 
-	if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
+	if (page < head ||
+	    (page >= head + max_t(unsigned long, compound_nr(head),
+				  (unsigned long)MAX_ORDER_NR_PAGES))) {
 		/*
 		 * Corrupt page, so we cannot call page_mapping. Instead, do a
 		 * safe subset of the steps that page_mapping() does. Caution:
@@ -109,6 +111,8 @@ void __dump_page(struct page *page, const char *reason)
 					head, compound_order(head),
 					head_compound_mapcount(head));
 		}
+		if (compound_order(head) == HPAGE_PUD_ORDER && PMDPageInPUD(page))
+			pr_warn("sub_compound_mapcount:%d\n", sub_compound_mapcount(page));
 	}
 	if (PageKsm(page))
 		type = "ksm ";
-- 
2.28.0