On Wed, Jun 27, 2007 at 07:32:45AM +0200, Nick Piggin wrote:

I think using fsblock to drive the IO and keep the pagecache flags
uptodate and using a btree in the filesystem to manage extents of block
allocations wouldn't be a bad idea though. Do any filesystems actually
do this?

Yes. XFS. But we still need to hold state in buffer heads (BH_delay,
BH_unwritten) that is needed to determine what type of
allocation/extent conversion is necessary during writeback. i.e.
what we originally mapped the page as during the ->prepare_write
call.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group

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