Re: Using ilookup?

[Andreas Dilger]

On Oct 13, 2004  14:42 +1300, Charles Manning wrote:
> YAFFS allocates its own "objectId"s which are used as inode numbers for most 
> purposes. When objects get deleted (== unlinked), the object numbers get 
> recycles.  Sometimes though the Linux cache has an inode after the object
> has been deleted. Then if that object id gets recycled before the cached
> inode is released, a problem occurs since iget() gets the old inode instead
> of creating a new one. We then end up with an inconsistency.

You can use iget4() along with a filesystem-specific comparison function,
which allows you to distinguish inodes with the same number based on
some extra data (e.g. generation number, 64-bit inode numbers, etc).  Is
there a reason to recycle the inode numbers, or could you just have a
32-bit counter?

> 1)  Somehow plug myself into the inode iput() chain so that I know when
> an inode is removed from the cache. I can then make sure that I don't
> free up the inode number for reuse until the inode is not in the cache.
> Any hints on how to do that?

You can use the ->delete_inode method which is a hook to be called
before/instead of the clear_inode() function in iput(), and is
the last thing action taken when the inode is being unlinked.  There
is also the ->clear_inode inode method, which is called when inodes
are being put away but not only when being unlinked.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://members.shaw.ca/adilger/             http://members.shaw.ca/golinux/

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