On Thu, Apr 26, 2007 at 04:53:00PM +0300, Avi Kivity wrote: > David Chinner wrote: > >The problem with this approach is that it turns around the whole > >way we look at bufferheads. Right now we have well defined 1:n > >mapping of page to bufferheads and so we tpyically lock the > >page first them iterate all the bufferheads on the page. > > > >Going the other way, we need to support m:n which we means > >the buffer has to become the primary interface for the filesystem > >to the page cache. i.e. we need to lock the bufferhead first, then > >iterate all the pages on it. This is messy because the cache indexes > >via pages, not bufferheads. hence a buffer needs to point to all the > >pages in it explicitly, and this leads to interesting issues with > >locking. > > > > Why is it necessary to assume that one filesystem block == one buffer? > Is it for atomicity, efficiency, or something else?
By definition, really - each filesystem block has it's own state and it's own disk mapping and so we need something to carry that information around.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
