On Tue, 2020-08-18 at 07:44 -0700, Jens Axboe wrote: > On 8/18/20 12:40 AM, Stefan Metzmacher wrote: > > Hi Jens, > > > > > > > > Will this be backported? > > > > > > > > > > I can, but not really in an efficient manner. It depends on > > > > > the async > > > > > buffered work to make progress, and the task_work handling > > > > > retry. The > > > > > latter means it's 5.7+, while the former is only in 5.9+... > > > > > > > > > > We can make it work for earlier kernels by just using the > > > > > thread offload > > > > > for that, and that may be worth doing. That would enable it > > > > > in > > > > > 5.7-stable and 5.8-stable. For that, you just need these two > > > > > patches. > > > > > Patch 1 would work as-is, while patch 2 would need a small > > > > > bit of > > > > > massaging since io_read() doesn't have the retry parts. > > > > > > > > > > I'll give it a whirl just out of curiosity, then we can > > > > > debate it after > > > > > that. > > > > > > > > Here are the two patches against latest 5.7-stable (the rc > > > > branch, as > > > > we had quite a few queued up after 5.9-rc1). Totally untested, > > > > just > > > > wanted to see if it was doable. > > > > > > > > First patch is mostly just applied, with various bits removed > > > > that we > > > > don't have in 5.7. The second patch just does -EAGAIN punt for > > > > the > > > > short read case, which will queue the remainder with io-wq for > > > > async execution. > > > > > > > > Obviously needs quite a bit of testing before it can go > > > > anywhere else, > > > > but wanted to throw this out there in case you were interested > > > > in > > > > giving it a go... > > > > > > Actually passes basic testing, and doesn't return short reads. So > > > at > > > least it's not half bad, and it should be safe for you to test. > > > > > > I quickly looked at 5.8 as well, and the good news is that the > > > same > > > patches will apply there without changes. > > > > Thanks, but I was just curios and I currently don't have the > > environment to test, sorry. > > > > Anoop: you helped a lot reproducing the problem with 5.6, would you > > be able to > > test the kernel patches against 5.7 or 5.8, while reverting the > > samba patches? > > See > > https://lore.kernel.org/io-uring/e22220a8-669a-d302-f454-03a35c9582b4@xxxxxxxxx/T/#t > > for the > > whole discussion? > > I'm actually not too worried about the short reads not working, it'll > naturally fall out correctly if the rest of the path is sane. The > latter > is what I'd be worried about! I ran some synthetic testing and > haven't > seen any issues so far, so maybe (just maybe) it's actually good. > > I can setup two branches with the 5.7-stable + patches and 5.8-stable > + > patches if that helps facilitate testing? That would be great. I took those two patches and tried to apply on top of 5.7.y. I had to manually resolve very few conflicts. I am not sure whether it is OK or not to test such a patched version(because of conflicts). Thanks, Anoop C S.
