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From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To: "Pali Rohár" <pali@kernel.org>
Cc: linux-fsdevel@vger.kernel.org,
	linux-ntfs-dev@lists.sourceforge.net, linux-cifs@vger.kernel.org,
	jfs-discussion@lists.sourceforge.net,
	linux-kernel@vger.kernel.org,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Jan Kara" <jack@suse.cz>, "Theodore Y . Ts'o" <tytso@mit.edu>,
	"Luis de Bethencourt" <luisbg@kernel.org>,
	"Salah Triki" <salah.triki@gmail.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Dave Kleikamp" <shaggy@kernel.org>,
	"Anton Altaparmakov" <anton@tuxera.com>,
	"Pavel Machek" <pavel@ucw.cz>, "Marek Behún" <marek.behun@nic.cz>,
	"Christoph Hellwig" <hch@infradead.org>
Subject: Re: [RFC PATCH 01/20] fat: Fix iocharset=utf8 mount option
Date: Sun, 15 Aug 2021 20:23:06 +0900	[thread overview]
Message-ID: <871r6vt0it.fsf@mail.parknet.co.jp> (raw)
In-Reply-To: <20210815094224.dswbjywnhvajvzjv@pali> ("Pali =?iso-8859-1?Q?Roh=E1r=22's?= message of "Sun, 15 Aug 2021 11:42:24 +0200")

To: Pali Rohár <pali@kernel.org>
Cc: linux-fsdevel@vger.kernel.org,  linux-ntfs-dev@lists.sourceforge.net,  linux-cifs@vger.kernel.org,  jfs-discussion@lists.sourceforge.net,  linux-kernel@vger.kernel.org,  Alexander Viro <viro@zeniv.linux.org.uk>,  Jan Kara <jack@suse.cz>,  "Theodore Y . Ts'o" <tytso@mit.edu>,  Luis de Bethencourt <luisbg@kernel.org>,  Salah Triki <salah.triki@gmail.com>,  Andrew Morton <akpm@linux-foundation.org>,  Dave Kleikamp <shaggy@kernel.org>,  Anton Altaparmakov <anton@tuxera.com>,  Pavel Machek <pavel@ucw.cz>,  Marek Behún <marek.behun@nic.cz>,  Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC PATCH 01/20] fat: Fix iocharset=utf8 mount option
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Gcc: nnimap+ibmpc.myhome.or.jp:Sent
--text follows this line--
To: Pali Rohár <pali@kernel.org>
Cc: linux-fsdevel@vger.kernel.org,  linux-ntfs-dev@lists.sourceforge.net,  linux-cifs@vger.kernel.org,  jfs-discussion@lists.sourceforge.net,  linux-kernel@vger.kernel.org,  Alexander Viro <viro@zeniv.linux.org.uk>,  Jan Kara <jack@suse.cz>,  "Theodore Y . Ts'o" <tytso@mit.edu>,  Luis de Bethencourt <luisbg@kernel.org>,  Salah Triki <salah.triki@gmail.com>,  Andrew Morton <akpm@linux-foundation.org>,  Dave Kleikamp <shaggy@kernel.org>,  Anton Altaparmakov <anton@tuxera.com>,  Pavel Machek <pavel@ucw.cz>,  Marek Behún <marek.behun@nic.cz>,  Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC PATCH 01/20] fat: Fix iocharset=utf8 mount option
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Gcc: nnimap+ibmpc.myhome.or.jp:Sent
--text follows this line--
Pali Rohár <pali@kernel.org> writes:

>> This change is not equivalent to utf8=1. In the case of utf8=1, vfat
>> uses iocharset's conversion table and it can handle more than ascii.
>> 
>> So this patch is incompatible changes, and handles less chars than
>> utf8=1. So I think this is clean though, but this would be regression
>> for user of utf8=1.
>
> I do not think so... But please correct me, as this code around is mess.
>
> Without this change when utf8=1 is set then iocharset= encoding is used
> for case-insensitivity implementation (toupper / tolower conversion).
> For all other parts are use correct utf8* conversion functions.
>
> But you use touppper / tolower functions from iocharset= encoding on
> stream of utf8 bytes then you either get identity or some unpredictable
> garbage in utf8. So when comparing two (different) non-ASCII filenames
> via this method you in most cases get that filenames are different.
> Because converting their utf8 bytes via toupper / tolower functions from
> iocharset= encoding results in two different byte sequences in most
> cases. Even for two utf8 case-insensitive same strings.
>
> But you can play with it and I guess it is possible to find two
> different utf8 strings which after toupper / tolower conversion from
> some iocharset= encoding would lead to same byte sequence.
>
> This patch uses for utf8 tolower / touppser function simple 7-bit
> tolower / toupper ascii function. And so for 7-bit ascii file names
> there is no change.
>
> So this patch changes behavior when comparing non 7-bit ascii file
> names, but only in cases when previously two different file names were
> marked as same. As now they are marked correctly as different. So this
> is changed behavior, but I guess it is bug fix which is needed.
> If you want I can put this change into separate patch.
>
> Issue that two case-insensitive same files are marked as different is
> not changed by this patch and therefore this issue stay here.

OK, sure. utf8 looks like broken than I was thinking (although user can
use iocharset=ascii and utf8=1 for this). The code might be better to
clean up a bit more though, looks like good basically.

One thing, please update FAT_DEFAULT_IOCHARSET help in Kconfig and
Documentation/filesystems/vfat.rst (with new warning about iocharset=utf8).

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

  reply	other threads:[~2021-08-15 11:23 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-08 16:24 [RFC PATCH 00/20] fs: Remove usage of broken nls_utf8 and drop it Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 01/20] fat: Fix iocharset=utf8 mount option Pali Rohár
2021-08-15  3:42   ` OGAWA Hirofumi
2021-08-15  9:42     ` Pali Rohár
2021-08-15 11:23       ` OGAWA Hirofumi [this message]
2021-08-23  3:51   ` Kari Argillander
2021-08-08 16:24 ` [RFC PATCH 02/20] hfsplus: Add iocharset= mount option as alias for nls= Pali Rohár
2021-08-09 17:51   ` Viacheslav Dubeyko
2021-08-09 20:49   ` Kari Argillander
2021-08-09 21:25     ` Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 03/20] udf: Fix iocharset=utf8 mount option Pali Rohár
2021-08-12 14:17   ` Jan Kara
2021-08-12 15:51     ` Pali Rohár
2021-08-13 13:48       ` Jan Kara
2021-08-19  8:34         ` Pali Rohár
2021-08-19 10:41           ` Jan Kara
2021-08-08 16:24 ` [RFC PATCH 04/20] isofs: joliet: " Pali Rohár
2021-08-12 14:18   ` Jan Kara
2021-08-08 16:24 ` [RFC PATCH 05/20] ntfs: Undeprecate iocharset= " Pali Rohár
2021-08-09 20:52   ` Kari Argillander
2021-08-19  1:21   ` Kari Argillander
2021-08-19  8:12     ` Pali Rohár
2021-08-19 10:23       ` Kari Argillander
2021-08-19 22:04         ` Pali Rohár
2021-08-19 23:18           ` Kari Argillander
2021-08-08 16:24 ` [RFC PATCH 06/20] ntfs: Fix error processing when load_nls() fails Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 07/20] befs: Fix printing iocharset= mount option Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 08/20] befs: Rename enum value Opt_charset to Opt_iocharset to match " Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 09/20] befs: Fix error processing when load_nls() fails Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 10/20] befs: Allow to use native UTF-8 mode Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 11/20] hfs: Explicitly set hsb->nls_disk when hsb->nls_io is set Pali Rohár
2021-08-09 17:31   ` Viacheslav Dubeyko
2021-08-09 17:37     ` Matthew Wilcox
2021-08-09 17:47       ` Pali Rohár
2021-08-09 20:43         ` Steve French
2021-08-09 18:00       ` Viacheslav Dubeyko
2021-08-08 16:24 ` [RFC PATCH 12/20] hfs: Do not use broken utf8 NLS table for iocharset=utf8 mount option Pali Rohár
2021-08-09 17:49   ` Viacheslav Dubeyko
2021-08-08 16:24 ` [RFC PATCH 13/20] hfsplus: " Pali Rohár
2021-08-09 17:42   ` Viacheslav Dubeyko
2021-08-08 16:24 ` [RFC PATCH 14/20] jfs: Remove custom iso8859-1 implementation Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 15/20] jfs: Fix buffer overflow in jfs_strfromUCS_le() function Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 16/20] jfs: Do not use broken utf8 NLS table for iocharset=utf8 mount option Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 17/20] ntfs: " Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 18/20] cifs: " Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 19/20] cifs: Remove usage of load_nls_default() calls Pali Rohár
2021-08-08 16:24 ` [RFC PATCH 20/20] nls: Drop broken nls_utf8 module Pali Rohár
2021-09-03 21:26 ` [RFC PATCH 00/20] fs: Remove usage of broken nls_utf8 and drop it Kari Argillander
2021-09-03 21:37   ` Pali Rohár
2021-09-03 22:06     ` Kari Argillander

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