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 56336606A320 for ; Wed, 28 Oct 2026 13:12:35 +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=rSAqWe2v; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=fGEzUaEr 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=mHGE9nXbxuB8GQ9t8LPv8LBGWevl1d8ukNIHXAQHhiw=; b=rSAqWe2vz4Gh4p shSJoH52HMTQYFquK4TKZeMMoYI4HzQxYCvUmFDopaV9RiihFCEn/LRt3QKeFuEPnrfVM/ZABCTIH T7hRsJEDkr5LIPvmskoWxmH6TOeJUrvOmZ+R3P0yMiHhH07+09t2Gt6akk4meg8uWRreNKtsMAQnF 9bj5isngnWkGENrqr9ANZfJ2Jp+f214l0UCSDvV3V8EJ/iwPnY+9y3mzZwm4x2d8kihhufYJQ98EU U52G+7r+m7KGoYbCjyDSikyrdHi+XBizHawdfgkNl425Eb1BWcWkP4dFF7ZP6bl2MiRkuk/9LmR3f P5KXa/QbHsTnW6EiwIIg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xM3SE-000000071nC-3PR7; Wed, 28 Oct 2026 13:12:34 +0000 Received: from out-252.mta1.migadu.com ([95.215.58.252] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xM3SB-000000071lr-3IyU for kexec@lists.infradead.org; Wed, 28 Oct 2026 13:12:33 +0000 X-Envelope-To: kexec@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=mHGE9nXbxuB8GQ9t8LPv8LBGWevl1d8ukNIHXAQHhiw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793193149; v=1; x=1793797949; b=fGEzUaEr8w61+lFUJkekZQi4IchHFI1oGuTpYnywD4uq7NYgtMIB4KLVEQTX9tu3L0+pzd7X uJGPjUqkyRJ7/LGJdP9Yu5YYeiFDulf+ETYGKM/YTzW7aaDU7ISl7xwUjOV6DayGav6115xQZ23 2+9Gu5zJq6L2EXkbbQRvZNpM= X-Envelope-To: kexec@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id db747fb4ed3da529; Wed, 28 Oct 2026 13:12:28 +0000 X-Mizu-Trace-ID: db747fb4ed3da529 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, stable@vger.kernel.org Subject: Re: [PATCH 11/46] mm/huge_memory: properly handle refcounted PUD mappings on fork Date: Wed, 28 Oct 2026 21:12:21 +0800 Message-ID: <20261028131221.42261-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261027-fixes_core-v1-11-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-11-6f74bec9a5bb@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-20261028_061231_972887_FAF6A5C9 X-CRM114-Status: UNSURE ( 6.00 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -2.1 (--) 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 Tue, Oct 27, 2026 at 12:17:31AM +0100, David Hildenbrand (Arm) wrote: >copy_huge_pud() copies device-DAX entries without taking a folio reference >or updating mapcounts and the child's RSS. > >For example, MADV_GUARD_INSTALL sets VM_MAYBE_GUARD on a device-DAX VMA, >forcing copy_page_range() to traverse the whole VMA on fork. Any remaining >huge PUDs are then copied without accounting for the new mappings. >Unmapping them in the child decrements accounting that was never added. > >Use vm_normal_page_pud() to identify refcounted mappings. Take a folio >reference and add the child's PUD rmap and RSS accounting before installing >the copied entry. Pass src and dst VMAs consistently instead of src and >dst MM. Move the TODO. > >Fixes: aed877c2b4257 ("device/dax: properly refcount device dax pages when mapping") >Cc: stable@vger.kernel.org >Signed-off-by: David Hildenbrand (Arm) >--- Reviewed-by: Lance Yang