Re: Long file names in VFAT broken with iocharset=utf8

Roland Kuhn
2007-05-07T18:07:41Z

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Hi Andrey!

On 7 May 2007, at 19:51, Andrey Borzenkov wrote:

> This was posted in one of Russian forums. It was not possible to
> archive
> (under Linux, using tar) vfat directory where files had long
> Russian names
> (really long - over 150 - 170 characters) - tar returned stat
> failure. When
> looking with plain ls, file names appeared truncated.
>
> Now looking at current (2.6.21) fat driver, __fat_readdir allocates
> large
> enough buffer (PAGE_SIZE-522) for UTF-8 name; but for
> iocharset=utf8 it calls
> uni16_to_x8() which artificially limits length of UTF-8 name to
> 256 ... which
> is obviously not enough for long UTF-8 Russian string (2 bytes per
> character)
> not to mention the - theoretical - general case of 6 bytes UTF-8
> characters.
>
> Similar problem has apparently vfat_lookup()->...->fat_search_long
> () call
> chain. Except this appears to be broken even in case of "utf8",
> because
> fat_search_long allocates fixed 256 bytes buffer for UTF-8 name.
>
> Am I off track here?
>
PATH_MAX specifically counts _bytes_ not characters, so UTF-8 does
not matter. ISTR that PATH_MAX was 256 at some point, but I just
quickly grepped /usr/include and found various mention of 4096, so
where's the central repository for this configuration item? A hard-
coded value of 256 somewhere inside the kernel smells like a bug.

Ciao,
Roland

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