From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CA8DF3BB113; Thu, 27 Aug 2026 11:18:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787829513; cv=none; b=EqHIIrPIVycYt7zRdeNFZA6Etc2DCjqBgAhOxe4Bxqms1BeqJA0gRGCPRIwYsnzIwYnzbKq+9hTYzwHz6POzOUqMxWn6ZJJ8AN6Os99EMUGC7hsyCNvVP3fI+xuLb0D5Je+VqqWcG6OIycO+Ih4Njx5k/78jZOoFpWUAllSHeWQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787829513; c=relaxed/simple; bh=+TRvDqchYoIwTYgqnq/cOtGwCvEcbUaVknQvACncHRU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lsZPf5MBhRkl2FxxafyXShUgrITPNW7Np5+yX9dyd4Ps85Z+hdYSDUJgexzvqVLAHtMRNrmUaRBxntdnrMI2h7Je41nBvOGFqgiqIsQUvP0hGyUNdnrOCq9VeYJpDeKPZQBFFHD3YTdc5YEmXDU7hucBNihOusZoBCnEwvEzLBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DC6qIxE0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DC6qIxE0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30FF01F000E9; Thu, 27 Aug 2026 11:18:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787829504; bh=UXfBo8v3K8VIzDSO2VHXgtuPrAb/8lRFr7BXsf++oYA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=DC6qIxE0KrdRhnwTpQj+mqOREb/P52l2gDOdyFApoE8VA1gv3wcCC3cG1+ykL3FjI gLV3FcWtR1+Q8HXEsmNwdHlWMLmr6Ox5CZzzOTla/i+4zIByVE+n7H9QeLbqUQogTP HINaxGjyQ2EfkOvrIiHXrZQ/YuvaW1nAJ04hK9lO596nhxDAP9PBO+TTzqNAXyYD8y jFe48V+dIKFBme7rHsNveL4VaiDtgdVQ6BFNh0GS6CIQwxW+R8p1M0PGA1lY/0j4F/ kjvulu43FN0rQAskUM5hgMh93Jh6XhGXLIM5ckhruJrXivG8JmUlG0gU47N82N0yaF KlpeMGvJUSCAQ== Date: Thu, 27 Aug 2026 12:18:14 +0100 From: "Lorenzo Stoakes (ARM)" To: Mike Rapoport Cc: Andrew Morton , David Hildenbrand , Baolin Wang , Barry Song , Dev Jain , Hugh Dickins , Jann Horn , Jason Gunthorpe , John Hubbard , Jonathan Corbet , Lance Yang , "Liam R. Howlett" , Masami Hiramatsu , Mathieu Desnoyers , Michal Hocko , Muchun Song , Nico Pache , Oscar Salvador , Pedro Falcato , Peter Xu , Ryan Roberts , Shakeel Butt , Shuah Khan , Steven Rostedt , Suren Baghdasaryan , Usama Arif , Vlastimil Babka , Zi Yan , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 6/6] userfaultfd: collapse VM_UFFD_{MISSING,WP,MINOR,RWP} into single VM_UFFD Message-ID: References: <20260823-uffd-vm-flags-v1-v1-0-3086981b33cf@kernel.org> <20260823-uffd-vm-flags-v1-v1-6-3086981b33cf@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Aug 27, 2026 at 12:16:32PM +0100, Lorenzo Stoakes (ARM) wrote: > So actually you're increasing by a cacheline and increasing the VMA size by > 64 bytes, i.e. 1/3, which is unacceptable obviously. > > Maybe there's something that can be done with: > > /* forced alignments: 1 */ > > Perhaps? But that looks potentially ugly. > I say elsewhere (or think I do) but to highlight - I think probably we could fix this by putting the flags in the low bits of vm_uffd_state.ctx? -- Cheers, Lorenzo