On Thu, Jan 20, 2011 at 12:33:46PM +1100, Dave Chinner wrote: > It's case b) that I'm mainly worried about, esp. w.r.t the 64k page > size on ia64/ppc. If we only track a single dirty bit in the page, > then every sub-page, non-appending write to an uncached region of a > file becomes a RMW cycle to initialise the areas around the write > correctly. The question is whether we care about this enough given > that we return at least PAGE_SIZE in stat() to tell applications the > optimal IO size to avoid RMW cycles. Note that this generally is only true for the first write into the region - after that we'll have the rest read into the cache. But we also have the same issue for appending writes if they aren't page aligned. > And if we only do IO on whole pages (i.e regardless of block size) > .writepage suddenly becomes a lot simpler, as well as being trivial > to implement our own .readpage/.readpages.... I don't think it simplifies writepage a lot. All the buffer head handling goes away, but we'll still need to do xfs_bmapi calls at block size granularity. Why would you want to replaced the readpage/readpages code? The generic mpage helpers for it do just fine. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
