[LTP] [PATCH 1/1] nfsstat01: Update client RPC calls for kernel 6.9

Fri Jul 12 02:40:58 CEST 2024

On Fri, 2024-07-12 at 08:58 +1000, NeilBrown wrote:
> On Fri, 12 Jul 2024, Jeff Layton wrote:
> > On Mon, 2024-07-08 at 17:49 +0000, Chuck Lever III wrote:
> > > 
> > > > On Jul 8, 2024, at 6:36 AM, Greg KH <greg@kroah.com> wrote:
> > > > 
> > > > On Sat, Jul 06, 2024 at 07:46:19AM +0000, Sherry Yang wrote:
> > > > > 
> > > > > 
> > > > > > On Jul 6, 2024, at 12:11 AM, Greg KH <greg@kroah.com> wrote:
> > > > > > 
> > > > > > On Fri, Jul 05, 2024 at 02:19:18PM +0000, Chuck Lever III wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > > On Jul 2, 2024, at 6:55 PM, Calum Mackay <calum.mackay@oracle.com> wrote:
> > > > > > > > 
> > > > > > > > To clarify…
> > > > > > > > 
> > > > > > > > On 02/07/2024 5:54 pm, Calum Mackay wrote:
> > > > > > > > > hi Petr,
> > > > > > > > > I noticed your LTP patch [1][2] which adjusts the nfsstat01 test on v6.9 kernels, to account for Josef's changes [3], which restrict the NFS/RPC stats per-namespace.
> > > > > > > > > I see that Josef's changes were backported, as far back as longterm v5.4,
> > > > > > > > 
> > > > > > > > Sorry, that's not quite accurate.
> > > > > > > > 
> > > > > > > > Josef's NFS client changes were all backported from v6.9, as far as longterm v5.4.y:
> > > > > > > > 
> > > > > > > > 2057a48d0dd0 sunrpc: add a struct rpc_stats arg to rpc_create_args
> > > > > > > > d47151b79e32 nfs: expose /proc/net/sunrpc/nfs in net namespaces
> > > > > > > > 1548036ef120 nfs: make the rpc_stat per net namespace
> > > > > > > > 
> > > > > > > > 
> > > > > > > > Of Josef's NFS server changes, four were backported from v6.9 to v6.8:
> > > > > > > > 
> > > > > > > > 418b9687dece sunrpc: use the struct net as the svc proc private
> > > > > > > > d98416cc2154 nfsd: rename NFSD_NET_* to NFSD_STATS_*
> > > > > > > > 93483ac5fec6 nfsd: expose /proc/net/sunrpc/nfsd in net namespaces
> > > > > > > > 4b14885411f7 nfsd: make all of the nfsd stats per-network namespace
> > > > > > > > 
> > > > > > > > and the others remained only in v6.9:
> > > > > > > > 
> > > > > > > > ab42f4d9a26f sunrpc: don't change ->sv_stats if it doesn't exist
> > > > > > > > a2214ed588fb nfsd: stop setting ->pg_stats for unused stats
> > > > > > > > f09432386766 sunrpc: pass in the sv_stats struct through svc_create_pooled
> > > > > > > > 3f6ef182f144 sunrpc: remove ->pg_stats from svc_program
> > > > > > > > e41ee44cc6a4 nfsd: remove nfsd_stats, make th_cnt a global counter
> > > > > > > > 16fb9808ab2c nfsd: make svc_stat per-network namespace instead of global
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > I'm wondering if this difference between NFS client, and NFS server, stat behaviour, across kernel versions, may perhaps cause some user confusion?
> > > > > > > 
> > > > > > > As a refresher for the stable folken, Josef's changes make
> > > > > > > nfsstats silo'd, so they no longer show counts from the whole
> > > > > > > system, but only for NFS operations relating to the local net
> > > > > > > namespace. That is a surprising change for some users, tools,
> > > > > > > and testing.
> > > > > > > 
> > > > > > > I'm not clear on whether there are any rules/guidelines around
> > > > > > > LTS backports causing behavior changes that user tools, like
> > > > > > > nfsstat, might be impacted by.
> > > > > > 
> > > > > > The same rules that apply for Linus's tree (i.e. no userspace
> > > > > > regressions.)
> > > > > 
> > > > > Given the current data we have, LTP nfsstat01[1] failed on LTS v5.4.278 because of kernel commit 1548036ef1204 ("nfs:
> > > > > make the rpc_stat per net namespace") [2]. Other LTS which backported the same commit are very likely troubled with the same LTP test failure.
> > > > > 
> > > > > The following are the LTP nfsstat01 failure output
> > > > > 
> > > > > ========
> > > > > network 1 TINFO: initialize 'lhost' 'ltp_ns_veth2' interface
> > > > > network 1 TINFO: add local addr 10.0.0.2/24
> > > > > network 1 TINFO: add local addr fd00:1:1:1::2/64
> > > > > network 1 TINFO: initialize 'rhost' 'ltp_ns_veth1' interface
> > > > > network 1 TINFO: add remote addr 10.0.0.1/24
> > > > > network 1 TINFO: add remote addr fd00:1:1:1::1/64
> > > > > network 1 TINFO: Network config (local -- remote):
> > > > > network 1 TINFO: ltp_ns_veth2 -- ltp_ns_veth1
> > > > > network 1 TINFO: 10.0.0.2/24 -- 10.0.0.1/24
> > > > > network 1 TINFO: fd00:1:1:1::2/64 -- fd00:1:1:1::1/64
> > > > > <<<test_start>>>
> > > > > tag=veth|nfsstat3_01 stime=1719943586
> > > > > cmdline="nfsstat01"
> > > > > contacts=""
> > > > > analysis=exit
> > > > > <<<test_output>>>
> > > > > incrementing stop
> > > > > nfsstat01 1 TINFO: timeout per run is 0h 20m 0s
> > > > > nfsstat01 1 TINFO: setup NFSv3, socket type udp
> > > > > nfsstat01 1 TINFO: Mounting NFS: mount -t nfs -o proto=udp,vers=3 10.0.0.2:/tmp/netpan-4577/LTP_nfsstat01.lz6zhgQHoV/3/udp /tmp/netpan-4577/LTP_nfsstat01.lz6zhgQHoV/3/0
> > > > > nfsstat01 1 TINFO: checking RPC calls for server/client
> > > > > nfsstat01 1 TINFO: calls 98/0
> > > > > nfsstat01 1 TINFO: Checking for tracking of RPC calls for server/client
> > > > > nfsstat01 1 TINFO: new calls 102/0
> > > > > nfsstat01 1 TPASS: server RPC calls increased
> > > > > nfsstat01 1 TFAIL: client RPC calls not increased
> > > > > nfsstat01 1 TINFO: checking NFS calls for server/client
> > > > > nfsstat01 1 TINFO: calls 2/2
> > > > > nfsstat01 1 TINFO: Checking for tracking of NFS calls for server/client
> > > > > nfsstat01 1 TINFO: new calls 3/3
> > > > > nfsstat01 1 TPASS: server NFS calls increased
> > > > > nfsstat01 1 TPASS: client NFS calls increased
> > > > > nfsstat01 2 TINFO: Cleaning up testcase
> > > > > nfsstat01 2 TINFO: SELinux enabled in enforcing mode, this may affect test results
> > > > > nfsstat01 2 TINFO: it can be disabled with TST_DISABLE_SELINUX=1 (requires super/root)
> > > > > nfsstat01 2 TINFO: install seinfo to find used SELinux profiles
> > > > > nfsstat01 2 TINFO: loaded SELinux profiles: none
> > > > > 
> > > > > Summary:
> > > > > passed 3
> > > > > failed 1
> > > > > skipped 0
> > > > > warnings 0
> > > > > <<<execution_status>>>
> > > > > initiation_status="ok"
> > > > > duration=1 termination_type=exited termination_id=1 corefile=no
> > > > > cutime=11 cstime=16
> > > > > <<<test_end>>>
> > > > > ltp-pan reported FAIL
> > > > > ========
> > > > > 
> > > > > We can observe the number of RPC client calls is 0, which is wired. And this happens from the kernel commit 57d1ce96d7655 ("nfs: make the rpc_stat per net namespace”). So now we’re not sure the kernel backport of nfs client changes is proper, or the LTP tests / userspace need to be modified.
> > > > > 
> > > > > If no userspace regression, should we revert the Josef’s NFS client-side changes on LTS?
> > > > 
> > > > This sounds like a regression in Linus's tree too, so why isn't it
> > > > reverted there first?
> > > 
> > > There is a change in behavior in the upstream code, but Josef's
> > > patches fix an information leak and make the statistics more
> > > sensible in container environments. I'm not certain that
> > > should be considered a regression, but confess I don't know
> > > the regression rules to this fine a degree of detail.
> > > 
> > > If it is indeed a regression, how can we go about retaining
> > > both behaviors (selectable by Kconfig or perhaps administrative
> > > UI)?
> > > 
> > 
> > I'd argue that the old behavior was a bug, and that Josef fixed
> > it. These stats should probably have been made per-net when all of the
> > original nfsd namespace work was done, but no one noticed until
> > recently. Whoops. 
> > 
> > A couple of hacky ideas for how we might deal with this:
> > 
> > 1/ add a new line to the output of /proc/net/rpc/nfsd. It could just
> > say "per-net\n" or "per-net <netns_id_number>\n" or something. nfsstat
> > should ignore it, but LTP test could look for it and handle it
> > appropriately. That could even be useful later for nfsstat too I guess.
> > 
> > 2/ move the file to a new name and make the old filename be a symlink
> > to the new one. nfsstat would still work, but LTP would be able to see
> > whether it was a symlink to detect the difference...or could just make
> > a new symlink that points to the file and LTP could look for its
> > presence.
> 
> I don't think it makes sense to present a solution which requires
> LTP to be modified.  If we are willing to modify LTP, then we should
> modify it to work with the per-net stats.
> 
> I think we need to create a new interface for the per-net stats, then
> deprecate the old interface and remove it in (say) 2 years.  That given
> LTP time to update, and means that an old LTP won't give incorrect
> numbers, it will simply fail.
> 
> All we need to do is bikeshed the new interface.
>   netlink ?
>   /proc/net/rpc-pernet/nfsd ?
> 
> This means that we still need to keep the combined stats, or to combine
> all the per-net stats on each access.
> 

How much of this functionality would we need to restore?

Prior to Josef's patches, you would get info about global stats from
relevant stats procfiles in a container. That seems like an information
leak to me, but fixing that is probably going to break _somebody_.
Where do we draw the line and why?

LTP is just a testsuite. Asking them to alter tests in order to cope
with a bugfix seems entirely reasonable to me. If someone can make a
case for real-world applications that rely on the old semantics, then
I'd be more open to changing this, but I just don't see the upside of
restoring legacy behavior here.
-- 
Jeff Layton <jlayton@kernel.org>