Re: [patch][rfc] mm: new address space calls

[Christoph Hellwig <hch@infradead.org>]

On Wed, Feb 25, 2009 at 03:59:57PM -0500, Chris Mason wrote:
> One problem I have with the btrfs extent state code is that I might
> choose to release the extent state in releasepage, but the VM might not
> choose to free the page.  So I've got an up to date page without any of
> the rest of my state.
> 
> Which of these ops covers that? ;)  I'd love to help better document the
> requirements for these callbacks, I find it confusing every time.

releasepage has also another problem.  It only gets called after
discard_buffer discarded lots of valuable information from the buffers,
which gets XFS into really bad trouble as that drops information if
there is a delalloc extent.

I'd really like to see some major overhaul in that area, and that also
extende to documentation (or just naming, why is block_invalidatepage
calling into a method called ->releasepage, but there also is a
->invalidatepage that gets called from truncate*page routines..)

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