Re: [CFT][PATCH] loopback fixes for 2.3

From: Alexander Viro (aviro@redhat.com)
Date: Sat Feb 12 2000 - 19:03:35 EST

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    On Sun, 13 Feb 2000, Andi Kleen wrote:

    > > The bottom line: encryption driver can trivially compensate for the change.
    > > So if it's a problem with on-disk format - fine, let's keep the transformation
    > > in the format-handling code.
    >
    > Unfortunately they can not. One design problem of loopback crypto is
    > that you cannot store any additional information. The only way to
    > check if the user entered the right password is to see if ext2 can mount
    > the file system. There is really no way to detect old and new format.

    HUH? You don't need the additional information. You need a different version
    of module that would work with 2.3/2.4 (and I hope that you didn't use
    loopback right before the change - it's severely fscked up as of 2.3.43).
    This version of module should take the page number/offset it got, take the
    lo->lo_dentry->d_inode->i_mapping, find mapping->bmap(mapping, block). That
    will be the on-disk block. What additional information are you talking about?
    Kernel version? lo->transfer() gets lo, it gets page->index, it gets offset
    within the page. What else do you need to calculate the physical block position
    (== old IV)?

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