On 03/09/2016 03:47 PM, Chuck Lever wrote: > >> On Mar 9, 2016, at 6:09 AM, Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx> wrote: >> >> >> >> On 08/03/2016 20:03, Chuck Lever wrote: >>> >>>> On Mar 8, 2016, at 12:53 PM, Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx> wrote: >>>> >>>> >>>> >>>> On 04/03/2016 18:28, Chuck Lever wrote: >>>>> If ib_post_send() in ro_unmap_sync() fails, the WRs have not been >>>>> posted, no completions will fire, and wait_for_completion() will >>>>> wait forever. Skip the wait in that case. >>>>> >>>>> To ensure the MRs are invalid, disconnect. >>>> >>>> How does that help to ensure that? >>> >>> I should have said "To ensure the MRs are fenced," >>> >>>> The first wr that failed and on will leave the >>>> corresponding MRs invalid, and the others will be valid >>>> upon completion. >>> >>> ? This is in the invalidation code, not in the fastreg >>> code. >> >> Yes, I meant linv... >> >>> When this ib_post_send() fails, I've built a set of >>> chained LOCAL_INV WRs, but they never get posted. So >>> there is no WR failure here, the WRs are simply >>> never posted, and they won't complete or flush. >> >> That's the thing, some of them may have succeeded. >> if ib_post_send() fails on a chain of posts, it reports >> which wr failed (in the third wr pointer). > > I see. > > >> 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? > > >>> 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. > > The xprtrdma completion handlers mark the MR associated with > a flushed LOCAL_INV WR "stale". They all have to be reset with > ib_dereg_mr to guarantee they are usable again. Have a look at > __frwr_recovery_worker(). > > And, xprtrdma waits for only the last LOCAL_INV in the chain to > complete. If that one isn't posted, then fr_done is never woken > up. In that case, frwr_op_unmap_sync() would wait forever. > > If I understand you I think the correct solution is for > frwr_op_unmap_sync() to regroup and reset the MRs associated > with the LOCAL_INV WRs that were never posted, using the same > mechanism as __frwr_recovery_worker() . > > It's already 4.5-rc7, a little late for a significant rework > of this patch, so maybe I should drop it? Git doesn't have any conflicts if I drop the patch from my tree, and I was still able to compile. Let me know if you want me to drop the patch from my tree, so you don't have to resend an entire series! Thanks, Anna > > > -- > 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
