From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.20 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793193153; b=adb4ZXM/rUMlbaFQSRhCnl8BxpdK5xUvwn/2IhwfTB8xL7tnxqOTmvBE+aK1ajhrZu9y ga0v9CXjP7PbmiXyv2sTmGmixgL15xW3wyq2ar2C+uKAJvgAfMjHZr3HFBtVkiMWS7z6K 7Vojwvv5nDgpCxoCIOTaGxKHKSCH/rpvy1DUDfKnhslX+KXyklRxn2JOcgO2MO4QYyDAr aUM4r9Me9ZCp9ONACt8qEzMZWiYrlt+6y1n/Q+296EaAQYLyJlWIHhIKPJQW0PFcW46Ft VIxM12D6sK9y/Giey912dMNs3gzgslsF0Iye39FlzQJS1WuzgR/JWw8S6oJihytZobw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793193153; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=mHGE9nXbxuB8GQ9t8LPv8LBGWevl1d8ukNIHXAQHhiw=; b=2jSFgf67nRevfa3dp5/mA3GQrpIgnD1nLtIgt78Ed21EBwLpDUca32cD7UShh+y57yjA nQkqxIkrCycKi4NyKQdCXmx7xJOzP6IvRCUwTmX3IjJl/CQPbSVy5O1r+uL1pjOHva/Sd vqqdHR8AHmfULEcQ/cMmlUIiBLU46zpr8zLQbf0gDrjxsDuQx7xXLIQUfSZoXzmNj4cRj TN1IAjvQ6a6WNUryG3kZ8pZ0Vn7oaLtrz60fAmkm/ibdKPdefxiGhHMbTTPahWvqpWfJ5 +FYrj9DSb2XY2u7PTgaG8gzhBU5DCA61AnXK82zS5G31fF71/DyagWsh70sXOK3OdNg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=fGEzUaEr; arc=none smtp.remote-ip=91.218.175.20 Received: from mta0.migadu.com (out-20.mta0.migadu.com [91.218.175.20]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 21DF8606A31D for ; Wed, 28 Oct 2026 13:12:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 21DF8606A31D Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=fGEzUaEr X-Envelope-To: linux-cxl@vger.kernel.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: linux-cxl@vger.kernel.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-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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