On Wed, May 12, 2010 at 05:24:04PM -0400, Josef Bacik wrote: > Hello, > > I just started adding aio_write to Btrfs and I noticed we're duplicating _alot_ > of the generic stuff in mm/filemap.c, even though the only thing thats really > unique is the fact that we copy userspace pages in chunks rather than one page a > t a time. What would be best is instead of doing write_begin/write_end with > Btrfs, it would be nice if we could just do our own perform_write instead of > generic_perform_write. This way we can drop all of these generic checks we have > that we copied from filemap.c and just got to the business of actually writing > the data. I hate to add another file operation, but it would _greatly_ reduce > the amount of duplicate code we have. If there is no violent objection to this > I can put something together quickly for review. Thanks, > I just got a suggestion from hpa about instead just moving what BTRFS does into the generic_perform_write. What btrfs does is allocates a chunk of pages to cover the entirety of the write, sets everything up, does the copy from user into the pages, and tears everything down, so essentially what generic_perform_write does, just with more pages. I could modify generic_perform_write and the write_begin/write_end aops to do this, where write_begin will return how many pages it allocated, copy in all of the userpages into the pages we allocated at once, and then call write_end with the pages we allocated in write begin. Then I could just make btrfs do write_being/write_end. So which option seems more palatable? Thanks, Josef -- 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
