On Wed, Aug 12 2009, Jens Axboe wrote: > On Thu, Aug 06 2009, Christoph Hellwig wrote: > > On Thu, Jul 30, 2009 at 11:23:56PM +0200, Jens Axboe wrote: > > > This is a first step at introducing per-bdi flusher threads. We should > > > have no change in behaviour, although sb_has_dirty_inodes() is now > > > ridiculously expensive, as there's no easy way to answer that question. > > > Not a huge problem, since it'll be deleted in subsequent patches. > > > > Looking at this again and again I don't really like this at all. What > > is the problem with having per-bdi flushing threads that just iterate > > a list of superblocks per-bdi and then the inodes from there? That > > would keep a lot of the calling conventions much more logical, as we > > have to writeback data per-sb for all data integrity and some other > > writes. > > OK, so you'd prefer leaving the super block lists in place and rather > have the super blocks hanging off the bdi? What about file systems that > support more than one block device per mount, like btrfs? Can we assume > that they will forever provide a single bdi backing? btrfs currently has > this, just wondering about future implications. Another issue with that approach is that you then need some logic to decide which lists to do first, how much, etc. A single list is nicely time ordered and retains our current approach, at least on a per-sb per device level. -- Jens Axboe -- 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
