On Tue, Jun 12 2007, Rusty Russell wrote: > On Mon, 2007-06-11 at 09:33 +0200, Jens Axboe wrote: > > On Mon, Jun 11 2007, Rusty Russell wrote: > > > So the problem is that I'd like to handle all of them, but I'm not clear > > > what requests my device can get. I can't see a source of any other type > > > of request. > > > > The other main request type is blk_pc_request(). In the data setup it's > > indentical to blk_fs_request(), there's a bio chain off ->bio. It's a > > byte granularity entity though, so you should check ->data_len for the > > size of it. ->cmd[] holds a SCSI cdb, which is the command you are > > supposed to handle. > > SCSI? I'm even more lost now. > > Q: So what *are* the commands? They are SCSI commands! > Q: Who puts them in my queue? If you want to support SG_IO for instance, you'd have to deal with SCSI commands. > I have *never* seen anything but an fs request come through to my > driver. You probably only did basic IO to it. > > Perhaps you are misunderstanding what the tag is? The tag is a unique > > identifier for a pending request, so you will by definition never have > > requests sharing a tag value. > > Yes, I started to suspect that. > > > But the tag is not to be considered as > > ordered, unless it has the barrier flag set as well. So you only need to > > serialize on the device side when blk_barrier_rq() is true. > > blk_barrier_rq(req) is never true. I put a BUG_ON(blk_barrier_rq(req)) > in my code and booted. This is using the device as a root ext3 > filesystem. > > I reverted all the tag changes, still no barriers. I added > "blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN, NULL);", > still no barriers. -o barrier=1 for ext3, it doesn't use barriers by default. Or barrier=flush for reiserfs. XFS defaults to barriers on. -- Jens Axboe _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
