From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 086343EA64 for ; Fri, 16 Aug 2024 03:42:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723779783; cv=none; b=OZ6miiy054DRHNhVemZg4TsXXFNCeSOgKcYPzeubP07f0UdpLq+pU+KkRbwgH8vCXcNBTmxCjCcJPXqZUoJKdxB5u7HpvNLJa6NNuS3BUMckPWH7vaSn3ByVh0ZbyUMrWWeG3Ia/b8eS1FzR5GVnR/9SBYcID7K5MSPaBd4jyJ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723779783; c=relaxed/simple; bh=JSeDhEpkVt7iOYFJaP+u0d3dSiwws2Pele+BVd4AgQw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=koAifUkuDsBZTTQL3LViC7hKpCsQKh5vzNJFWVPwNZFiO80YUL80U8jypCsgOS3/TzeX5MPwO/h10VKScSk5JbfhzMyE0ylb7Au0Ci979tvqkx3PbUy8LGa4zLL4v4C/CZgRDSh8SP5GauUrdpzNrPUfmYFRItFynFKucDBooog= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=OjwPN/33; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OjwPN/33" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=AUsOavIE8dxCHAG65JW9tarGXEp0lmQXHgPOb8+iEwg=; b=OjwPN/335UEp/RsJH48FT+j1FJ y24YeEN50R09pRYv4Y8+6uST73J1AUH0KJf4fXsi72fPIaElTZaY4v7dUGEmQCm2Wp+QPoAqY9pQB 4Efi79WM9NNLAJfFwBeCUiavcHZO3LPFjPDwMX4fXtxjLwBT2L7xWnyw5I98jmXzBaVGqg7JLi9ok q7FhiBlMLZqcwK0ZYqsQGLx/UvZtiQxE4drwZDuXs2V82NqUFkE+sJYYVtS/Nkw78mJaiEvPdLuN0 LtHQ4WtHW/Wl41PzTnKPtXE9i+5pDYE41O4CQ9DDdXSfxE5OCnOPm9u8M+N1j5qZH5/Q5lCUak4D5 xCpzJF5A==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1senrb-00000002xhn-0v9J; Fri, 16 Aug 2024 03:42:55 +0000 Date: Fri, 16 Aug 2024 04:42:55 +0100 From: Matthew Wilcox To: David Hildenbrand Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC] Merge PG_private_2 and PG_mappedtodisk Message-ID: References: <7e7ee391-6f4d-4d36-ace5-4f8ca81479bc@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <7e7ee391-6f4d-4d36-ace5-4f8ca81479bc@redhat.com> On Thu, Aug 15, 2024 at 11:41:23PM +0200, David Hildenbrand wrote: > On 14.08.24 19:36, Matthew Wilcox wrote: > > I believe these two flags have entirely disjoint uses and there will > > be no confusion in amalgamating them. > > > > Anonymous memory (re)uses mappedtodisk for anon_exclusive. > > Anonymous memory does not use PG_private_2. > > Also not when they are in the swapcache, right? Correct, swapcache has no use of PG_private_2. > > The one thing that's going to stand in the way of this is that various > > parts of the VFS treat private_2 as a "wait for this bit to be clear", > > due to its use in fscache (which is going away). > > > > So my approach here is going to be: > > > > - Rename mappedtodisk to be PG_owner_priv_2 (add appropriate aliases) > > - Switch btrfs to use owner_priv_2 instead of private_2 > > - Wait for the fscache use of private2 to finish its deprecation cycle > > - Remove private_2 entirely > > > > Sound good? > > Yes, one step into the right direction. Cool, thanks.