linux-kernel - Re: CONFIG_VFAT_FS

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Message-ID: <87tz1up8kc.fsf@devron.myhome.or.jp>
Date:	Fri, 03 Jul 2009 15:46:59 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	tridge@...ba.org
Cc:	Jan Engelhardt <jengelh@...ozas.de>, Theodore Tso <tytso@....edu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Pavel Machek <pavel@....cz>, john.lanza@...ux.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>, corbet@....net,
	jcm@...masters.org
Subject: Re: CONFIG_VFAT_FS_DUALNAMES regressions

tridge@...ba.org writes:

> right, that is not unexpected. It creates both the long name and the
> short name in this case as the short name is constrained to not be
> case preserving, and the filesystem normally tries to be both
> case-insensitive and case-preserving. As the long name has no
> constraints on the case of characters it creates both so that devices
> (like your camera I think) that only look at the 8.3 entries will see
> a file.
>
> That is why setting shortname=winnt is desirable when using the "no
> dualnames" patch I posted. That tells Linux to behave more like what
> current windows versions behave, which is to try and put it in the 8.3
> entry if it can, even if it is all lowercase.
>
> What I would like to see us do for maximum compatibility with devices
> like this, while still maximising the legal safety, is to take mixed
> case prefixes or suffixes that fit in 8.3 and uppercase them and set
> the CASE_LOWER_BASE and CASE_LOWER_EXT bits appropriately in the flags
> field, and not store a long name. That would makes us really nicely
> compatible with devices like your camera, at the price of losing mixed
> case preservation for 8.3 names.
>
> It would be another departure from previous behaviour however, so I
> want to get some feedback from Hirofumi-san first. 

I guess it would be depending on how many shortname only devices are
there though. At least for now, I'd like to keep that small.

Thanks.

> btw, if you still think your camera really is looking at the long
> filename entries, then try creating a file like DsCf2000.jpg with a
> unpatched kernel, mounted with shortname=winnt. That will create two
> directory entries for the file, one being DSCF2000.JPG and the other
> being DsCf2000.jpg.
>
> Then view the list of photos on the LCD back panel of your
> camera. Assuming it has a way to see the filename, does it display the
> mixed case name DsCf2000.jpg, or does it display a non-mixed name like
> dscf2000.jpg or DSCF2000.JPG.
>
> If it displays a mixed name (ie. DsCf) then your camera can indeed
> read long filename entries. If it displays a all uppercase or all
> lowercase name then I think it is only capable of reading short names
> from FAT filesystems. That is what I think you will find.
>
> Cheers, Tridge

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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