From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44424606A32C for ; Tue, 3 Nov 2026 06:26:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=fSRpCbAi; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=BrQ5Opza DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=89WHsBI4UooPN0e/fzWqgj/M9hLD/tFhYxvpr6aA8I0=; b=fSRpCbAiVgn6qa 9/W+DMQl46VeIuFsH8ijc2YalhCfFy1KsY4doZFQ+wGHKquBOmDC/k+Xc0t8I7kmFNpJeYNGmqFnt cm6o/Mh7Mn+AwefDlgXy0Lx+BMsIYGENaI4Q2+Edk+FlC6gRCXDB0W8wyYOYdXFQPulXGlUfhXWOK kJFcXoAoe/91+YFr6j9pfdMtXAknx2lg3BheTIXYu4280ieVW/qOxmDo/LS3vSKPTPdF+4+MmqMMF 3inzgMDU6KFaNlODWZ1jBR8m19NxzjpUZu3LlOFvVnqL3Ylz7EzsUVDY+CH0J9NNELn356P9mbtL0 6bAO9vE6Nq+fvFU1ZKlQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xO7yk-00000001F4x-3Sls; Tue, 03 Nov 2026 06:26:42 +0000 Received: from out-167.mta1.migadu.com ([95.215.58.167] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xO7yg-00000001F4O-1WZV for kexec@lists.infradead.org; Tue, 03 Nov 2026 06:26:40 +0000 X-Envelope-To: kexec@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=R4qncA5U596ba8pavgxH4k05FBMaxgAUsAOufRDPVI0=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793687194; v=1; x=1794291994; b=BrQ5OpzasmaKN5c4rG+lUhIWYHYwU9Zu/yaL7ECDfW6bWPv8oJYd/xoJtaPXoBVLlimlpMUD hxMHJYVuqCPlSy9lE3cTmbFIqjIxFUJWVmK1PEWGFGvTx3eyIQsy580HKxs6eKEmRludRp7iNyI 96WyFglyjScKawmHaqcOgHAs= X-Envelope-To: kexec@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id 650e1e2cc95fd22e; Tue, 03 Nov 2026 06:26:33 +0000 X-Mizu-Trace-ID: 650e1e2cc95fd22e X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kees@kernel.org, peterz@infradead.org, jannh@google.com, pfalcato@suse.de, hughd@google.com, pasha.tatashin@soleen.com, pratyush@kernel.org, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, lance.yang@linux.dev, riel@surriel.com, harry@kernel.org, apopple@nvidia.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, jhubbard@nvidia.com, peterx@redhat.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, osalvador@suse.de, minchan@kernel.org, muchun.song@linux.dev, xu.xin@linux.dev, chengming.zhou@linux.dev, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, youngjun.park@lge.com, gourry@gourry.net, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, jgg@ziepe.ca, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, mason@kernel.org, stable@vger.kernel.org, usama.anjum@arm.com Subject: Re: [PATCH v3 38/47] mm: fix deadlock of mremap() against UFFDIO_MOVE Date: Tue, 3 Nov 2026 14:26:28 +0800 Message-ID: <20261103062628.92242-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261031-fixes_core-v3-38-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-38-d6437171ecc3@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261102_222638_690856_8E763EA0 X-CRM114-Status: UNSURE ( 8.17 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -2.8 (--) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-13.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sat, Oct 31, 2026 at 10:40:07AM +0100, David Hildenbrand (Arm) wrote: >From: Chris Mason > >With per-VMA locks, UFFDIO_MOVE can run concurrently with mremap() >on different VMAs in the same mm. Those VMAs can share page tables, so >both operations can acquire the same pair of page-table locks. > >UFFDIO_MOVE orders the locks by address, while mremap() takes the source >lock first. These conflicting orders can deadlock; mremap() holding >mmap_lock for writing no longer helps. > >Move double_pt_lock() and double_pt_unlock() to mm/internal.h and use >them for all page-table moves in mremap(). Preserve the source entry >checks after acquiring both locks. Remove the comments claiming that >exclusive mmap_lock makes lock ordering irrelevant. > >In move_ptes(), make sure to just recheck source and destination PMD >after taking the locks and drop the overly-long comment. > >Fix generated by an LLM and sent by Chris Mason in private. > >[ david: use new helpers consistently; simplify description and comments; > move_ptes() fixup ] > >Fixes: 867a43a34ff8 ("userfaultfd: use per-vma locks in userfaultfd operations") >Cc: stable@vger.kernel.org >Signed-off-by: Chris Mason >Reviewed-by: Lorenzo Stoakes (ARM) >Acked-by: Muchun Song >Tested-by: Muhammad Usama Anjum >Signed-off-by: David Hildenbrand (Arm) >--- Nothing jumped out at me, so: Reviewed-by: Lance Yang