> On Jun 6, 2017, at 4:23 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Tue, Jun 06, 2017 at 04:16:53PM -0400, Chuck Lever wrote: >> >>> On Jun 6, 2017, at 4:15 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: >>> >>> On Tue, Jun 06, 2017 at 03:45:59PM -0400, Chuck Lever wrote: >>>> >>>>> On Jun 6, 2017, at 3:41 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: >>>>> >>>>> On Tue, Jun 06, 2017 at 03:35:23PM -0400, Chuck Lever wrote: >>>>>> I filed https://bugzilla.linux-nfs.org/show_bug.cgi?id=306 >>>>>> >>>>>> To check memory allocation latency, I could always construct >>>>>> a framework around kmalloc and alloc_page. >>>>>> >>>>>> >>>>>> I've also found some bad behavior around proto=rdma,sec=krb5i. >>>>>> When I run a heavy I/O workload (fio, for example), every so >>>>>> often a read operation fails with EIO. I dug into it a little >>>>>> and MIC verification fails for these replies on the client. >>>>> >>>>> Do we still have the problem that the read data can change between the >>>>> time we calculate the MIC and the time we transmit the data to the >>>>> client? >>>> >>>> I don't see a problem with krb5p, which, if IIUC, would also >>>> fall victim to this situation, unless there is much stricter >>>> request serialization going on with krb5p. >>> >>> We turn off zero-copy by clearing RQ_SPLICE_OK in the krb5p case. >> >> Seems like this is the right answer for krb5i too. Shall I try that? > > Sure! Just grep around for RQ_SPLICE_OK, I think it should be easy to > figure out. I added clear_bit(RQ_SPLICE_OK, &rqstp->rq_flags); at the top of unwrap_integ_data() in net/sunrpc/auth_gss/svcauth_gss.c. I haven't seen a failure yet, which is a good sign. > --b. >> >> >>>> Even so, how would I detect if this issue was present? >>> >>> Good question. If you knew the data and mic in the bad case, and had >>> some way to guess what the previous data might have been based on what >>> you knew about the test, then you could try mic's of likely older >>> versions of the data and see if you get a match.... That sounds hard. >>> >>> --b. >> >> -- >> Chuck Lever -- 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
