On Mon, 4 Jul 2016, Lars Ellenberg wrote: > On Thu, Jun 30, 2016 at 07:15:18PM -0400, Mike Snitzer wrote: > > > Lars, please feel free to see if this set addresses the similar deadlock > > > you saw/fixed with drbd. > > I'm pretty sure it will help, but will confirm. > > > > We need to converge on an acceptable fix for > > > this problem -- preferably sooner rather than later! > > > > > > Conversely, Mikulas: if you can easily reproduce the dm-snapshot > > > deadlock please try Lars' fix to see if it is workable for our DM needs. > > > > I hadn't reviewed Lars' patch yet but Mikulas pointed out to me that > > Lars' patch is focused on the blk_queue_split() path -- and given that > > DM doesn't use this function (nor do DM devices even have a 'bio_split' > > bioset, see commit dbba42d8a9e) it won't fix the DM (snapshot) deadlock. > > Don't you get it implicitly when using dm-mq -> blk-mq? > > Lars There were observed deadlocks just between dm targets, caused by queuing bios on current->bio_list. The underlying block device was not involved in the deadlocks. Therefore I conclude that changing the behavior of blk_queue_split would not resolve these deadlocks (because dm targets do not use blk_queue_split). Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
