From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F99EC46469 for ; Wed, 12 Sep 2018 10:36:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AEAAD206BB for ; Wed, 12 Sep 2018 10:36:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AEAAD206BB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mail.parknet.co.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727753AbeILPkO (ORCPT ); Wed, 12 Sep 2018 11:40:14 -0400 Received: from mail.parknet.co.jp ([210.171.160.6]:57162 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726855AbeILPkO (ORCPT ); Wed, 12 Sep 2018 11:40:14 -0400 Received: from ibmpc.myhome.or.jp (server.parknet.ne.jp [210.171.168.39]) by mail.parknet.co.jp (Postfix) with ESMTPSA id 3548A15AF4A; Wed, 12 Sep 2018 19:36:17 +0900 (JST) Received: from devron.myhome.or.jp (foobar@devron.myhome.or.jp [192.168.0.3]) by ibmpc.myhome.or.jp (8.15.2/8.15.2/Debian-11) with ESMTPS id w8CAaFMI030465 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Sep 2018 19:36:16 +0900 Received: from devron.myhome.or.jp (foobar@localhost [127.0.0.1]) by devron.myhome.or.jp (8.15.2/8.15.2/Debian-11) with ESMTPS id w8CAaFQE010409 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Sep 2018 19:36:15 +0900 Received: (from hirofumi@localhost) by devron.myhome.or.jp (8.15.2/8.15.2/Submit) id w8CAaFkg010408; Wed, 12 Sep 2018 19:36:15 +0900 From: OGAWA Hirofumi To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] fat: Relax checks for sector size and media type References: <20180902131932.11558-1-pali.rohar@gmail.com> <87bm9ft5h5.fsf@mail.parknet.co.jp> <20180903074005.7e3guj24ksq2l44c@pali> <874lf7t3gg.fsf@mail.parknet.co.jp> <20180903080422.ta3clnhr5bobv6il@pali> <87zhwzro1o.fsf@mail.parknet.co.jp> <20180912101750.6slpi3puoww72xsj@pali> Date: Wed, 12 Sep 2018 19:36:15 +0900 In-Reply-To: <20180912101750.6slpi3puoww72xsj@pali> ("Pali =?iso-8859-1?Q?Roh=E1r=22's?= message of "Wed, 12 Sep 2018 12:17:50 +0200") Message-ID: <878t47roio.fsf@mail.parknet.co.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Pali Rohár writes: >> If there is real user to use that, I'm ok though (of course, need >> serious tests). However, FAT would be for exchange data with other >> devices, and there is "cluster per sector", and spec recommends sector >> size == device sector size. So I suspect this format is not useful. > > I looked into OpenBSD, FreeBSD and NetBSD source code and there is no > explicit upper limit for sector size. Just that sector size must be > power of two. > > I have not did tests yet, but you are right that some testing should be > done. > > As FAT operates with clusters and cluster size is defined by sector > size, then sectors per cluster and sector size defines cluster size. And > cluster size itself implies maximal size of FAT filesystem. > > So increasing sector size could be useful to create larger FAT32 > filesystems as current limit hit by sector size = 512 bytes. > > What do you think, which operating systems should be tested? Again, I suspect those custom extension (can't read by some uefi or windows) is not useful though. Testing on kernel that has PAGE_SIZE >= 8192, and setting FAT sector_size >= 8192. After that, it would be safe to remove 4096 limitation. Thanks. -- OGAWA Hirofumi