> On Mar 10, 2016, at 10:54 AM, Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> wrote: > >>>>>>>> Moving the QP into error state right after with rdma_disconnect >>>>>>>> you are not sure that none of the subset of the invalidations >>>>>>>> that _were_ posted completed and you get the corresponding MRs >>>>>>>> in a bogus state... >>>>>>> >>>>>>> Moving the QP to error state and then draining the CQs means >>>>>>> that all LOCAL_INV WRs that managed to get posted will get >>>>>>> completed or flushed. That's already handled today. >>>>>>> >>>>>>> It's the WRs that didn't get posted that I'm worried about >>>>>>> in this patch. >>>>>>> >>>>>>> Are there RDMA consumers in the kernel that use that third >>>>>>> argument to recover when LOCAL_INV WRs cannot be posted? >>>>>> >>>>>> None :) >>>>>> >>>>>>>>> I suppose I could reset these MRs instead (that is, >>>>>>>>> pass them to ib_dereg_mr). >>>>>>>> >>>>>>>> Or, just wait for a completion for those that were posted >>>>>>>> and then all the MRs are in a consistent state. >>>>>>> >>>>>>> When a LOCAL_INV completes with IB_WC_SUCCESS, the associated >>>>>>> MR is in a known state (ie, invalid). >>>>>>> >>>>>>> The WRs that flush mean the associated MRs are not in a known >>>>>>> state. Sometimes the MR state is different than the hardware >>>>>>> state, for example. Trying to do anything with one of these >>>>>>> inconsistent MRs results in IB_WC_BIND_MW_ERR until the thing >>>>>>> is deregistered. >>>>>> >>>>>> Correct. >>>>>> >>>>> >>>>> It is legal to invalidate an MR that is not in the valid state. So you >>> don't >>>>> have to deregister it, you can assume it is valid and post another LINV > WR. >>>> >>>> I've tried that. Once the MR is inconsistent, even LOCAL_INV >>>> does not work. >>>> >>> >>> Maybe IB Verbs don't mandate that invalidating an invalid MR must be > allowed? >>> (looking at the verbs spec now). >> > > IB Verbs doesn't have specify this requirement. iW verbs does. So transport > independent applications cannot rely on it. So ib_dereg_mr() seems to be the > only thing you can do. > >> If the MR is truly invalid, then there is no issue, and >> the second LOCAL_INV completes successfully. >> >> The problem is after a flushed LOCAL_INV, the MR state >> sometimes does not match the hardware state. The MR is >> neither registered or invalid. >> > > There is a difference, at least with iWARP devices, between the MR state: VALID > vs INVALID, and if the MR is allocated or not. > >> A flushed LOCAL_INV tells you nothing more than that the >> LOCAL_INV didn't complete. The MR state at that point is >> unknown. >> > > With respect to iWARP and cxgb4: when you allocate a fastreg MR, HW has an entry > for that MR and it is marked "allocated". The MR record in HW also has a state: > VALID or INVALID. While the MR is "allocated" you can post WRs to invalidate it > which changes the state to INVALID, or fast-register memory which makes it > VALID. Regardless of what happens on any given QP, the MR remains "allocated" > until you call ib_dereg_mr(). So at least for cxgb4, you could in fact just > post another LINV to get it back to a known state that allows subsequent > fast-reg WRs. > > Perhaps IB devices don't work this way. > > What error did you get when you tried just doing an LINV after a flush? With CX-2 and CX-3, after a flushed LOCAL_INV, trying either a FASTREG or LOCAL_INV on that MR can sometimes complete with IB_WC_MW_BIND_ERR. -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
