On Mon, Aug 10, 2015 at 05:27:18PM -0400, Chuck Lever wrote:
>
> On Aug 10, 2015, at 5:05 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> > On Fri, Aug 07, 2015 at 04:55:46PM -0400, Chuck Lever wrote:
> >> Both commit 0380a3f375 ("svcrdma: Add a separate "max data segs"
> >> macro for svcrdma") and commit 7e5be28827bf ("svcrdma: advertise
> >> the correct max payload") are incorrect. This commit reverts both
> >> changes, restoring the server's maximum payload size to 1MB.
> >>
> >> Commit 7e5be28827bf based the server's maximum payload on the
> >> _client's_ RPCRDMA_MAX_DATA_SEGS value. That was wrong.
> >>
> >> Commit 0380a3f375 tried to fix this so that the client maximum
> >> payload size could be raised without affecting the server, but
> >> managed to confuse matters more on the server side.
> >>
> >> More importantly, limiting the advertised maximum payload size was
> >> meant to be a workaround, not the actual fix. We need to revisit
> >>
> >> https://bugzilla.linux-nfs.org/show_bug.cgi?id=270
> >>
> >> A Linux client on a platform with 64KB pages can overrun and crash
> >> an x86_64 NFS/RDMA server when the r/wsize is 1MB. An x86/64 Linux
> >> client seems to work fine using 1MB reads and writes when the Linux
> >> server's maximum payload size is restored to 1MB.
> >>
> >> BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=270
> >> Fixes: 0380a3f375 ("svcrdma: Add a separate "max data segs" macro")
> >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> >> ---
> >>
> >> Hi Bruce-
> >>
> >> I notice you still have "svcrdma: Boost NFS READ/WRITE payload
> >> size maximum" in both your nfsd-next and for-4.3 branches. Can
> >> you please replace that patch with this one? This patch uses
> >> the approach we agreed on several weeks ago.
> >>
> >> Thanks!
> >
> > Gah, I don't like rebasing those for-XXX branches, but OK, done. In the
> > future I'd prefer incremental patches against those branches if at all
> > possible.
>
> Thanks for taking the update!
>
> I thought you were going to wait for v2 of that series.
>
> http://marc.info/?l=linux-nfs&m=143680563000597&w=2
Yeah, that was probably my screwup.
--b.
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