On 9/12/21 12:21 PM, Nadav Amit wrote: > > >> On Sep 12, 2021, at 11:15 AM, Jens Axboe <axboe@xxxxxxxxx> wrote: >> >> On 9/11/21 8:34 PM, Nadav Amit wrote: >>> Hello Jens (& Pavel), >>> >>> I hope you are having a nice weekend. I ran into a KASAN failure in io-uring >>> which I think is not "my fault". >>> >>> The failure does not happen very infrequently, so my analysis is based on >>> reading the code. IIUC the failure, then I do not understand the code well >>> enough, as to say I do not understand how it was supposed to work. I would >>> appreciate your feedback. >>> >>> The failure happens on my own custom kernel (do not try to correlate the line >>> numbers). The gist of the splat is: >> >> I think this is specific to your use case, but I also think that we >> should narrow the scope for this type of REQ_F_REISSUE trigger. It >> really should only happen on bdev backed regular files, where we cannot >> easily pass back congestion. For that case, the completion for this is >> called while we're in ->write_iter() for example, and hence there is no >> race here. >> >> I'll ponder this a bit… > > I see what you are saying. The assumption is that write_iter() is setting > REQ_F_REISSUE, which is not the case in my use-case. Yes exactly, and hence why I think we need to tighten this check to only be for bdev backed files. > Perhaps EAGAIN is > anyhow not the right return value (in my case). I am not sure any other > “invalid" use-case exists, but some documentation/assertion(?) can help. > > I changed the return error-codes and check that the issue is not > triggered again. > > Thanks, as usual, for the quick response. OK good, thanks for confirming! -- Jens Axboe
