linux-kernel - Long file names in VFAT broken with iocharset=utf8

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Date:	Mon, 7 May 2007 21:51:14 +0400
From:	Andrey Borzenkov <arvidjaar@...l.ru>
To:	hirofumi@...l.parknet.co.jp
Cc:	linux-kernel@...r.kernel.org
Subject: Long file names in VFAT broken with iocharset=utf8

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?

-andrey

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