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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id y9-20020a4ac409000000b0049e9a80c690sm2014172oop.1.2022.11.18.17.35.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Nov 2022 17:35:17 -0800 (PST) Date: Fri, 18 Nov 2022 17:35:05 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Yu Zhao , Linus Torvalds , Johannes Weiner , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Vlastimil Babka , Peter Xu , Yang Shi , John Hubbard , Mike Kravetz , Sidhartha Kumar , Muchun Song , Miaohe Lin , Naoya Horiguchi , Mina Almasry , James Houghton , Zach O'Keefe , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 1/3 fix] mm,thp,rmap: subpages_mapcount of PTE-mapped subpages: fix In-Reply-To: <759077a6-a08-5bb0-a0b6-53be2fe8b56a@google.com> Message-ID: <7a4f5e5e-de33-dace-c526-4a3d3cf5f6e0@google.com> References: <5f52de70-975-e94f-f141-543765736181@google.com> <78fa518-85b5-32c0-ee92-537fa46131f6@google.com> <759077a6-a08-5bb0-a0b6-53be2fe8b56a@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668821718; a=rsa-sha256; cv=none; b=7Xdg1HfpEKxc3kMzADcsINfW2Mjoj10DiM7wh+60pNo8qrUuwwpQcsse2ZVcuRlh/vo55B 7ZUr1ES1Pwh/a3VyzZcVF4e1ZiEtJM6Ft5fVQGMIYVVuTTfX8Zx49rGtTX6p6qU1QiIwz9 s4V4xYtyajLZj8oUYbs5Hy5mKbtwn4Q= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=niWUweP5; spf=pass (imf18.hostedemail.com: domain of hughd@google.com designates 209.85.167.175 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668821718; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Tj3z/V74h8yTKGx3pmSAn8bqVk2d50oyi+g/jzPn/nQ=; b=An60xEJGQlMR2PCpTl9dONZboC056BVfF9vjJdm/DyTUnJfBUQzgd96eBp0A8DDZqbxciG LZ7dagOAjjPvJ0e1R6CXgfS9cOjqy3/HpoL3obf1nCrqCCW9aHehPueetRIv8N5/mbj2Cf J6O4JEU82XXsN7WLYfeLoa2MqpdfGF4= X-Stat-Signature: i383ak87kc4x6dp57xhdixai4uougap1 X-Rspamd-Queue-Id: 8C9B81C000B X-Rspamd-Server: rspam01 X-Rspam-User: Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=niWUweP5; spf=pass (imf18.hostedemail.com: domain of hughd@google.com designates 209.85.167.175 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1668821718-298191 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: Yu Zhao reports compiler warning in page_add_anon_rmap(): mm/rmap.c:1236:13: warning: variable 'first' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized] } else if (PageTransHuge(page)) { ^~~~~~~~~~~~~~~~~~~ mm/rmap.c:1248:18: note: uninitialized use occurs here VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); ^~~~~ We do need to fix that, even though it's only uninitialized in an impossible condition: I've chosen to initialize "first" true, to minimize the BUGs it might then hit; but you could just as well choose to initialize it false, to maximize the BUGs it might hit. Reported-by: Yu Zhao Signed-off-by: Hugh Dickins --- mm/rmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/rmap.c b/mm/rmap.c index 66be8cae640f..25b720d5ba17 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1281,7 +1281,7 @@ void page_add_anon_rmap(struct page *page, struct compound_mapcounts mapcounts; int nr = 0, nr_pmdmapped = 0; bool compound = flags & RMAP_COMPOUND; - bool first; + bool first = true; if (unlikely(PageKsm(page))) lock_page_memcg(page); -- 2.35.3