On Mon 07-11-11 12:00:41, Dmitry Monakhov wrote: > On Fri, 28 Oct 2011 14:34:31 +0900, Kazuya Mio <k-mio@xxxxxxxxxxxxx> wrote: > > 2011/10/25 22:40, Jan Kara wrote: > > > Please no. Generally this boils down to what do we do with dirty data > > > when there's error in writing them out. Currently we just throw them away > > > (e.g. in media error case) but I don't think that's a generally good thing > > > because e.g. admin may want to copy the data to other working storage or > > > so. So I think we should rather keep the data and provide a mechanism for > > > userspace to ask kernel to get rid of the data (so that we don't eventually > > > run OOM). > > > > I see. I agree with you. > > > > >> Do you have any ideas? > > > So the question is what would you like to achieve. If you just want to > > > unblock a thread then a solution would be to make a thread at > > > balance_dirty_pages() killable. If generally you want to get rid of dirty > > > memory, then I don't have a really good answer but throwing dirty data away > > > seems like a bad answer to me. > > > > The problem is that we cannot unmount the corrupted filesystem due to > > un-killable dd process. We must bring down the system to resume the service > > with no dirty pages. I think it is important for the service continuity > > to be able to kill the thread handling in balance_dirty_pages(). > In fact you are very lucky because dd is just deadlocked, in many cases > journal abort result in BUG_ON triggering(if IO load is high enough). Can you provide the exact kernel message? I'd be interested... > This is because transaction abort check is racy. Right now i've no good > fix which has reasonable performance. My latest idea is to protect > transaction abort check via SRCU. Yeah, the code does not seem to care about races too much but I don't see which BUG_ON would be triggered... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
