2011/10/9 Shaohua Li <shli@xxxxxxxxxx>: > 2011/10/9 Mike Snitzer <snitzer@xxxxxxxxxx>: >> On Sat, Oct 08 2011 at 7:02am -0400, >> Shaohua Li <shli@xxxxxxxxxx> wrote: >> >>> Looks the dm request based flush logic is broken. >>> >>> saved_make_request_fn >>> __make_request >>> blk_insert_flush >>> but blk_insert_flush doesn't put the original request to list, instead, the >>> q->flush_rq is in list. >>> then >>> dm_request_fn >>> blk_peek_request >>> dm_prep_fn >>> clone_rq >>> map_request >>> blk_insert_cloned_request >>> so q->flush_rq is cloned, and get dispatched. but we can't clone q->flush_rq >>> and use it to do flush. map_request even could assign a different blockdev to >>> the cloned request. >> >> You haven't explained why cloning q->flush_rq is broken. What is the >> problem with map_request changing the blockdev? For the purposes of >> request-based DM the flush machinery has already managed the processing >> of the flush at the higher level request_queue. > hmm, looks I overlook the issue. cloned flush_rq has some problems but can > be fixed. > 1. it doesn't set requet->bio, request->bio_tail > 2. REQ_CLONE_MASK should set REQ_FLUSH_SEQ oh, don't need set REQ_FLUSH_SEQ, the low level queue will set it anyway. sorry for the noise. Jeff's patch looks ok then. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
