Le jeudi 27 mars 2014 à 10:45 +0200, Ilya Dryomov a écrit : > On Thu, Mar 27, 2014 at 9:48 AM, Olivier Bonvalet <ceph.list@xxxxxxxxx> wrote: > > Le mercredi 26 mars 2014 à 15:58 -0500, Alex Elder a écrit : > >> Olivier reports that with the simple patch I provided > >> (which changed a "<" to a "!=" and removed an assertion) > >> he is running successfully. > >> > >> To me this is fantastic news, and you can see I posted > >> a patch with the fix. > >> > >> There remains a race condition though, one which I described > >> in a separate message earlier today. I don't think it will > >> prove to be a problem in practice, but I agreed to work on > >> a fix to ensure the race condition is eliminated. It will > >> require some work with reference counting image and object > >> requests. > >> > >> The fix won't be coming today. But I aim to provide it > >> in a matter of several days. > >> > >> -Alex > >> > > > > One question from one of my customers : why am I the only one to > > complain about that problem ? > > I know that Ceph users often use qemu/librbd instead of kernel client, > > but what is the trigger of those «race condition» ? Having "multiple > > requests" per RBD image ? It should be a normal use, no ? > > > > If someone can help me give an explanation, thanks :) > > We've had a couple more, similar reports in the last few months. > However you are the first reporter who was able to trigger this race > often enough to track it down. This race condition (read: bug) is > kernel client specific, qemu/librbd is unaffected. Having an rbd > request that spans multiple RADOS objects and therefore results in > multiple object requests is normal use, it's just that particular piece > of code turned out to be prone to a subtle race. You have to keep in > mind that races are all about timing and relative order of events, so > simply issuing a multi-object rbd request is not enough to trigger it, > stars have to align too ;) > > Thanks, > > Ilya > Great, thanks ! Olivier -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
