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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rnJLf-00000006u48-3pIq; Thu, 21 Mar 2024 14:24:51 +0000 From: "Matthew Wilcox (Oracle)" To: Andrew Morton Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, David Hildenbrand , Vlastimil Babka , Miaohe Lin , Muchun Song , Oscar Salvador Subject: [PATCH 8/9] mm: Improve dumping of mapcount and page_type Date: Thu, 21 Mar 2024 14:24:46 +0000 Message-ID: <20240321142448.1645400-9-willy@infradead.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240321142448.1645400-1-willy@infradead.org> References: <20240321142448.1645400-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C545EA0019 X-Stat-Signature: pxr3pqk7uxyz4gmp4fbiktmzw3ewq6ne X-HE-Tag: 1711031100-254725 X-HE-Meta: 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 0OZkjT+R q/3iR3ytlY/w6vaRFtOBZrOlU5RChNFIM1O9n4aFxP5SiG2B/zcV/KHcU9T/2kubYQ6o0XaIozH7x/vqQujrS0p+xMEfB4r4HN03Ig5t9IhWOJdD5rHFH9fbPkC4R3WH9II76NyAHOj/GGtB0hAQ+wUYqrLImUWfU4nH2ZS50NsS2kgursw/m6VmZaDJ8Jez+xWMRXf3t5C5PZsKMX3VNff3UHVFTCbub1usw X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: For pages that have a page_type, set the mapcount to 0, which will reduce the confusion in people reading page dumps ("Why does this page have a mapcount of -128?"). Now that hugetlbfs is a page_type, read the entire_mapcount for any large folio; this is fine for all folios as no user reuses the entire_mapcount field. For pages which do not have a page type, do not print it to reduce clutter. Signed-off-by: Matthew Wilcox (Oracle) --- mm/debug.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) diff --git a/mm/debug.c b/mm/debug.c index c1c1a6a484e4..e8a96b8b7197 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -55,18 +55,14 @@ static void __dump_folio(struct folio *folio, struct page *page, unsigned long pfn, unsigned long idx) { struct address_space *mapping = folio_mapping(folio); - int mapcount = 0; + int mapcount = atomic_read(&page->_mapcount) + 1; char *type = ""; - /* - * page->_mapcount space in struct page is used by slab pages to - * encode own info, and we must avoid calling page_folio() again. - */ - if (!folio_test_slab(folio)) { - mapcount = atomic_read(&page->_mapcount) + 1; - if (folio_test_large(folio)) - mapcount += folio_entire_mapcount(folio); - } + /* Open-code page_mapcount() to avoid looking up a stale folio */ + if (mapcount < 0) + mapcount = 0; + if (folio_test_large(folio)) + mapcount += folio_entire_mapcount(folio); pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", folio_ref_count(folio), mapcount, mapping, @@ -99,7 +95,8 @@ static void __dump_folio(struct folio *folio, struct page *page, */ pr_warn("%sflags: %pGp%s\n", type, &folio->flags, is_migrate_cma_folio(folio, pfn) ? " CMA" : ""); - pr_warn("page_type: %pGt\n", &folio->page.page_type); + if (page_has_type(&folio->page)) + pr_warn("page_type: %pGt\n", &folio->page.page_type); print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32, sizeof(unsigned long), page, -- 2.43.0