Return-Path: Date: Tue, 6 Jun 2017 16:23:07 -0400 From: "J. Bruce Fields" To: Chuck Lever Cc: Benjamin Coddington , Linux NFS Mailing List Subject: Re: GSS sequence number window Message-ID: <20170606202307.GI13376@fieldses.org> References: <63736845-2BD3-4EE1-AC12-0BD21A9ABEF2@oracle.com> <20170530193419.GA9371@fieldses.org> <20170531192231.GA23526@fieldses.org> <28665890-C74A-4319-B42E-475393821EC7@oracle.com> <20170606194158.GG13376@fieldses.org> <4D542D55-DCBA-4838-9DB2-B76B4068783E@oracle.com> <20170606201504.GH13376@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-ID: On Tue, Jun 06, 2017 at 04:16:53PM -0400, Chuck Lever wrote: > > > On Jun 6, 2017, at 4:15 PM, J. Bruce Fields 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 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. --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 > >