From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7862621E0AF; Tue, 25 Nov 2025 17:21:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764091288; cv=none; b=NbpuXN0h7dGGuPu6Cv+hyg3O5s5t3tIzwRwVQTRy/Bs9b5kklIBSYa1HoPt6A/yiUI9BuFROFvAaGRJuOTAaxIJYfj8UllUDmRzpSDu52csxsiEpcVR/sugA639Ssh1kfOyMoMgjBvTH3/aF/3baGi09ChLog52xvs2jWTWXVzc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764091288; c=relaxed/simple; bh=5V9QV7SiBzMU5nx3Mn2uqFLHCyID9A3N1YOoa6yxqY4=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=O4d5Qyn4DibshRfrK3pvDt0ciTQHiT+wbKg9Ugt6PWw/u34R9z/mBOfVVKXNhTlRD/v2Itp+2iBQ6hsct+XNxdgdJZjt1rmSaLH8CSc+TnXqTxHMfNB8PST37hkLNp4MBt7mdakvKLJwKtWfGlNGkziVdxkwn+nUzeO4vZUhCOE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=f0+AP+ps; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="f0+AP+ps" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9F6FC4CEF1; Tue, 25 Nov 2025 17:21:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1764091288; bh=5V9QV7SiBzMU5nx3Mn2uqFLHCyID9A3N1YOoa6yxqY4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=f0+AP+psoLoGzXaq00ep6BDykJP5aOdtZfoQZ4KAyuamvgXUZO/UGmEJZu88bAQIq Ph+B0PjesF0Ac7gLWJ9KCv+Omr0a+hSLWs0rbzhWkIUTz4dhCv1QM8hBT4VZXdt0Tw qAckYaIks0SEUeBlWRsbMccDVtm+g6LfRTNVGc0U= Date: Tue, 25 Nov 2025 09:21:25 -0800 From: Andrew Morton To: Lorenzo Stoakes Cc: Muchun Song , Oscar Salvador , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Axel Rasmussen , Yuanchu Xie , Wei Xu , Peter Xu , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Kees Cook , Matthew Wilcox , Jason Gunthorpe , John Hubbard , Leon Romanovsky , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Xu Xin , Chengming Zhou , Jann Horn , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Pedro Falcato , Shakeel Butt , David Rientjes , Rik van Riel , Harry Yoo , Kemeng Shi , Kairui Song , Nhat Pham , Baoquan He , Chris Li , Johannes Weiner , Qi Zheng , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , Bjorn Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , rust-for-linux@vger.kernel.org Subject: Re: [PATCH v3 0/4] initial work on making VMA flags a bitmap Message-Id: <20251125092125.3e425e05382642ddff2db496@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit On Tue, 25 Nov 2025 10:00:58 +0000 Lorenzo Stoakes wrote: > We are in the rather silly situation that we are running out of VMA flags > as they are currently limited to a system word in size. > > This leads to absurd situations where we limit features to 64-bit > architectures only because we simply do not have the ability to add a flag > for 32-bit ones. > > This is very constraining and leads to hacks or, in the worst case, simply > an inability to implement features we want for entirely arbitrary reasons. > > This also of course gives us something of a Y2K type situation in mm where > we might eventually exhaust all of the VMA flags even on 64-bit systems. > > This series lays the groundwork for getting away from this limitation by > establishing VMA flags as a bitmap whose size we can increase in future > beyond 64 bits if required. All added to mm-unstable, thanks.