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Fri, 21 Mar 2025 12:02:57 +0000 (UTC) Received: from gshan-thinkpadx1nanogen2.remote.csb (unknown [10.64.136.79]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D3C981801752; Fri, 21 Mar 2025 12:02:51 +0000 (UTC) From: Gavin Shan To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, willy@infradead.org, david@redhat.com, vbabka@suse.cz, linmiaohe@huawei.com, gehao@kylinos.cn, shan.gavin@gmail.com Subject: [PATCH v2 2/2] mm/debug: Fix parameter passed to page_mapcount_is_type() Date: Fri, 21 Mar 2025 22:02:22 +1000 Message-ID: <20250321120222.1456770-3-gshan@redhat.com> In-Reply-To: <20250321120222.1456770-1-gshan@redhat.com> References: <20250321120222.1456770-1-gshan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Queue-Id: F0F2C4000A X-Stat-Signature: qnyddp7ug6pfw5b71o14a3p4pdy6ikpm X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1742558583-407761 X-HE-Meta: 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 CQL8922l U0JFENfNgnS1ui1DKd92yjeA7xoLVIs63jYE7FiU6d7rHH0SpvIQ9foKo60HRF1dCMfhcXr2sjcaTbjcYsAa8ieFev5eNJ83lID5/LfEO95WQMyPDNivM9VQpz1pdwRtWeIpz+G0LICaIm5RroJrHjbgaxqWAc/LgDeRkYdy9ANVxgcjMKRcQRi2pweAEU7jNcEa7psW+jAxklFHOWJhdd40o+MC4TRiXYYNu/K6L7VunBi3g5etXdhXUyvoEVL9WHl5vIbKglk7AIx0M3gXsnwuEbhXlCvWQZTtgJzvJ5vXmLB3ebF1y1XtlWDiISHw36EXYsAsPtpSIkPHW53lbU1H4SHXot9XjD63UZ0HzZVm8iocStPlBud0df6wI8jPRXI4FxLM8InjBy5nd2yx1SNKBSpkpZV2j8mtzInOr29EA99nfB7kR7aMv1VP3bZZBqcfofGTbSw0VRzw= 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: As the comments of page_mapcount_is_type() indicate, the parameter passed to the function should be one more than page->_mapcount. However, page->_mapcount is passed to the function by commit 4ffca5a96678 ("mm: support only one page_type per page") where page_type_has_type() is replaced by page_mapcount_is_type(), but the parameter isn't adjusted. Fix the parameter for page_mapcount_is_type() to be (page->__mapcount + 1). Note that the issue doesn't cause any visible impacts due to the safety gap introduced by PGTY_mapcount_underflow limit. Fixes: 4ffca5a96678 ("mm: support only one page_type per page") Signed-off-by: Gavin Shan Acked-by: David Hildenbrand Acked-by: Vlastimil Babka --- mm/debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/debug.c b/mm/debug.c index 8d2acf432385..b6bd9555ec7b 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -71,10 +71,10 @@ 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 = atomic_read(&page->_mapcount); + int mapcount = atomic_read(&page->_mapcount) + 1; char *type = ""; - mapcount = page_mapcount_is_type(mapcount) ? 0 : mapcount + 1; + mapcount = page_mapcount_is_type(mapcount) ? 0 : mapcount; pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", folio_ref_count(folio), mapcount, mapping, folio->index + idx, pfn);