On Sun, Jul 29, 2007 at 04:09:20PM +0400, Alex Tomas wrote: > David Chinner wrote: > >On Fri, Jul 27, 2007 at 11:51:56AM +0400, Alex Tomas wrote: > >But this is really irrelevant - the issue at hand is what we want > >for VFS level delalloc support. IMO, that mechanism needs to support > >both XFS and ext4, and I'd prefer if it doesn't perpetuate the > >bufferhead abuses of the past (i.e. define an iomap structure > >instead of overloading bufferheads yet again). > > I'm not sure I understand very well. ->get_blocks abuses bufferheads to provide an offset/length/state mapping. That's all it needs. That what the iomap structure is used for. It's smaller than a bufferhead, it's descriptive of it's use and you don't get it confused with the other 10 ways bufferheads are used and abused. > where would you track uptodate, dirty and other states then? > do you propose to separate block states from block mapping? No. They still get tracked in the bufferheads attached to the page. That's what bufferheads were originally intended for(*). Cheers, Dave. (*) I recently proposed a separate block map tree for this rather than using buffer heads for this because of the memory footprint of N bufferheads per page on contiguous mappings. That's future work, not something we really need to consider here. Chris Mason's extent map tree patches are a start on this concept. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
