From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0FD592D876B for ; Thu, 16 Jul 2026 04:57:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784177837; cv=none; b=LoMgN0JEdFCRejR+oBN8f0TYa8Ru2/yS2Uw7h03zGnDLTKr4DLDI46H3N6oU3LvMKtT0bOjP0acSVi9CUCjefKQ9RdDMA8NJkAAtXTTXkRVTa6nO1DFuS2y7JAWU+5+tjTMRRwyd4ggBugtzTlx8FAkChE8L3mYFb8zZK5eJ6W8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784177837; c=relaxed/simple; bh=T+w3KKKZd3ndOAYZWOt6qNJb9Iq3+HWEXjZeQ+XUo0g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rlFSfjAgNbLy+dMw4/tBpFl05gR8KEGQARen7OFd9EK3O4L7wrYyFVN2O2g0P8nu4AhG8kh3o9voc/15pbkAiqYhMQSTP01p+eWMrn0pVwoDbSK9BPuiSzZYDaerD9ajy3d900E5EJEfq75AVQ8qavm+Ru99vEyBfR6Q6gkxSJs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=dAzAqH5L; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="dAzAqH5L" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CB96F1477; Wed, 15 Jul 2026 21:57:09 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 426A23F7D8; Wed, 15 Jul 2026 21:57:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784177834; bh=T+w3KKKZd3ndOAYZWOt6qNJb9Iq3+HWEXjZeQ+XUo0g=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dAzAqH5LmxVasJEmpNTlRwMhjim3NeWFinBXl7c7Sw+fSA28vkOuP0ej2S7tEAkmF nvFe1Y/bTIBK27+aRTNhSqLeEaqXYLrbhLUiDkJai86cN95Oi5uoMdcshD25YNXfyG vLCALjqJf+hfqVqGdCSRe2nvh0YAEAk5Gsh0s4mc= Message-ID: Date: Thu, 16 Jul 2026 10:27:05 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] Batch unmap of uffd-wp file folios To: Andrew Morton Cc: david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, riel@surriel.com, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260715111839.1667914-1-dev.jain@arm.com> <20260715115852.a32e472d97fa182d6a5ee482@linux-foundation.org> Content-Language: en-US From: Dev Jain In-Reply-To: <20260715115852.a32e472d97fa182d6a5ee482@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/07/26 12:28 am, Andrew Morton wrote: > On Wed, 15 Jul 2026 11:18:33 +0000 Dev Jain wrote: > >> Currently, batched unmapping is supported if: >> >> 1) folio is a file folio, not belonging to uffd-wp VMA >> 2) folio is anonymous and not swapbacked (lazyfree), not belonging to >> uffd-wp VMA >> >> So the cases which are not supported are >> >> 1) folio belonging to uffd-wp VMA >> 2) folio is anonymous and swapbacked >> >> It is easy to see that this adds a lot of cognitive load while reading >> try_to_unmap_one - we need to remember throughout whether nr_pages == 1 >> or > 1. >> >> The uffd-wp handling in try_to_unmap_one is regarding preserving the >> uffd-wp state for file folios via pte_install_uffd_wp_if_needed (for anon >> folio, we handle that while constructing the swap pte). >> >> Stop special casing on uffd-wp VMAs by simply adding batching support >> to pte_install_uffd_wp_if_needed. > > Thanks, I'll await reviewer input on this. > > Sashiko might have found a pre-existing issue: > https://sashiko.dev/#/patchset/20260715111839.1667914-1-dev.jain@arm.com That was unexpected from Sashiko. "When a large folio registered with uffd-wp is unmapped via try_to_unmap_one(), folio_unmap_pte_batch() batches and clears multiple PTEs." At patch 2, there is no batching support yet for uffd-wp folios.