[OpenAFS] Some questions (Linux-oriented)

[Derek Atkins]

Frank Baumgart <frank.baumgart@esc-electronics.de> writes:

> > As I learned, the reiserfs does not have the inode-abstraction that is
> > needed for a proper functioning of AFS. The ext2 as well as ext3 does.
> 
> reiserfs does not have inodes, that's true, but it has some object-id
> mechanism to kind of simulate them because they are required for NFS
> as well.
> It should be possible to use this for AFS, too, but I can not remember
> to have seen ANY AFS-related messages on the reiserfs developer list
> since at least early '99.

The problem with AFS cache on reiserfs is that the reiserfs
violates the inode abstraction.  The user-space application runs
a 'stat' on the file, reads the inode number, and passes that
inode number down into the kernel.  With reiserfs this information
is _INSUFFICIENT_ to grab into the real file inode.

reiserfs uses a 32-bit inode number and a 32-bit "magic number".
Unfortunately there is no way to get this magic-number from
user-space.

When linux moves to 64-bit inode numbers then this should be fixed
because then reiserfs can make the 64-bit inode number be a
combination of the 32-bit inode and 32-bit magic.  I'm not holding
my breath.

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
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