On Mon, 01/04 13:16, Stefan Hajnoczi wrote: > On Wed, Dec 23, 2015 at 06:15:20PM +0800, Fam Zheng wrote: > > On Fri, 12/18 14:15, Markus Armbruster wrote: > > In that theory, all other block job types, mirror/stream/commit, fit into a > > "pull" model, which follows a specified dirty bitmap and copies data from a > > specified src BDS. In this pull model, > > > > mirror (device=d0 target=d1) becomes a pull fileter: > > > > BB[d0] BB[d1] > > | | > > throttle [pull,src=d0] > > | | > > detect-zero detect-zero > > | | > > copy-on-read copy-on-read > > | | > > BDS BDS > > > > Note: the pull reuses most of the block/mirror.c code except the > > s->dirty_bitmap will be initialized depending on the block job type. In the > > case of mirror, it is trivially the same as now. > > I don't understand the pull filter. Is there also a mirror block job > coroutine? > > Does anything perform I/O to BB[d1]?
Yes, the filter will have a mirror block job coroutine, and it writes to the BDS behind BB[d1]. This is conceptually different from the "block jobs have their own BBs" design. > > If nothing is writing to/reading from BB[d1], then I don't understand > the purpose of the pull filter. > > Stefan
