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

OGAWA Hirofumi
2007-05-07T18:28:14Z

Hi,

Roland Kuhn <rkuhn@e18.physik.tu-muenchen.de> writes:

>> 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.

There is a nasty issue here. FAT is limited by 255 unicode chars or so.
So, we would need to count number of unicode chars of filename.

That's not implemented currently.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>