[Fwd: Bug in Linux VFAT filesystem: truncating file to greather size!]

From: Ivan Baldo (lubaldo@adinet.com.uy)
Date: Fri Oct 27 2000 - 19:43:46 EDT

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            Hello.
            I have sent this to the maintainer of the VFAT code some time ago and
    it told me it doesn't have time.
            It seems there is a bug and this bug still persists in 2.2.17 and
    2.4.0-test9 (test9 says there is a bug on file.c line 69 and sometimes
    on line 79 I think, I think this is the file.c of VFAT which has code
    for reporting that bug on those lines).
            Also note that there is a bug in kernel 2.4.0-test9 regarding to long
    filenames on VFAT32 filesystems (it doesn't create them ok, test with
    Scandisk or Norton Disk Doctor), you can easily check that.
            Sorry this is somewhat vague, but I don't have much free time right
    now, yet I will try to answer your questions or try to help you as much
    as I can, so don't doubt to email me (I am not on the mailing list!).
            I hope you can reproduce both of this bugs and fix them.
            Thank you very much guys!

            Here is the email I sent to the maintainer:

    -------- Original Message --------
    From: Ivan Baldo <lubaldo@adinet.com.uy>
    Subject: Bug in Linux VFAT filesystem: truncating file to greather size!
    To: chaffee@bmrc.cs.berkeley.edu
    CC: SET <salvador@inti.gov.ar>, Gonzalo Piano <mpsggpep@adinet.com.uy>

            Hello.
            Please, if it is not you the correct person to email the bug, then
    point me in the right direction and excuse me.
            Do this:
                    - create a small C program that calls the "truncate()" function to
    increase the size of an already existing file. Note that I am saying
    *increase the size*, wich it is different from *truncating the file*.
    Make sure the file is in a mounted VFAT filesystem and that both the
    file and the increase in size are big (use 1mb for created file and
    increase it to 2mb for example, or use greater random values).
                    - unmount filesystem and check with your favourite program (I have
    used Microsoft Scandisk and Norton Disk Doctor, I have not tryed
    dosfsck...). Your checking program will say that the file has some sort
    of bad allocation issues, etc. Don't worry, it does not seem to kill the
    filesystem, only the file you created and tested.

            Tested with home-compiled 2.2.15 Kernel, I have used GCC 2.95.2 and
    binutils 2.9.5.0.22, most of the things are compiled statically (not as
    modules), the filesystem things are all compiled statically. Another
    friend tested with its 2.2.15 kernel, *and* another friend tested with
    its 2.0.38 kernel!!! In all cases we have managed to reproduce the
    problem! I have a little C program for doing this... it is in spanish
    language but I think you will not need it... anyway, if you want this
    program I can translate a bit of it (the code...) and send it to you.

            I haven't researched which kernel doesn't has the bug, because I don't
    have older kernels (disk space and cleaning issues and my internet
    connection isn't very cheap) and because I have a big lack of free time.

            I hope you can reproduce the problem and fix it easily.
            If you want more information and maybe some more help (take in account
    that I am not a very knowledgeable person... so I can do only easy
    things...), then just email me! Maybe you want me to test a patch or
    something...

            Ok, thanks you so much! Bye.

    P.s.: Netscape Messenger seems to rely on the ability to truncate a file
    to a bigger size, but it uses it only for non important files (the
    message files doesn't seem to have this problem, but the .summary files
    do).

    -- 
    Ivan Baldo:
    lubaldo@adinet.com.uy - http://members.xoom.com/baldo - ICQ 10215364
    Phone: (598) (2) 613 3223.
    Caldas 1781, Malvin, Montevideo, Uruguay, South America.
    

    (If you have problems with the previous addresses, try this ones: ibaldo@usa.net, http://baldo.home.ml.org).

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