On Wed, Apr 09, 2014 at 10:12:58AM -0400, Trond Myklebust wrote:
>
> On Apr 9, 2014, at 9:56, Dr Fields James Bruce <bfields@xxxxxxxxxxxx> wrote:
>
> > On Wed, Apr 09, 2014 at 09:41:28AM -0400, Trond Myklebust wrote:
> >> According to RFC5661, NFS4ERR_REP_TOO_BIG/NFS4ERR_REP_TOO_BIG_TO_CACHE
> >> are only appropriate if "The reply to a Compound would exceed the
> >> channel's negotiated maximum response size.”. Given that the callers
> >> of nfsd4_encode_fattr appear to all pass in ‘buffer’ and ‘buflen’
> >> arguments that are limited to single page, doesn’t this mean that you
> >> can end up returning nfs4err_resource in cases where
> >> nfserr_rep_too_big/nfserr_rep_too_big_to_cache are simply not
> >> appropriate?
> >
> > Yes, you're right. This will be fixed by later patches which remove
> > those arbitrary single-page limits, but for now it's a bug.
> >
> > This was probably a bad way to sequence those patches.
> >
> > That said, all that patch is doing in those cases is replacing one
> > useless error by another, so in practice I don't think reverting the
> > patch would help anyone--so I'm inclined to leave this alone and wait
> > for the real bug to be fixed (which is that we're imposing limits other
> > than the session limits).
> >
> > Is this causing some problem right now?
> >
>
> I’m not aware of any bug reports yet, but I did want to make sure that it was on your radar.
>
> That said, one immediate consequence of this patch will be that NFSv4.1 clients will now report EIO instead of EREMOTEIO if they hit the problem. That may make debugging a little less obvious.
> Another consequence will be that if we ever do try to add client side handling of NFS4ERR_REP_TOO_BIG, then we now have to deal with the “handle existing buggy server” syndrome.
Yeah, OK, I can see it would be annoying; maybe it's worth something
like the following for 3.15?
And then for 3.16 I'll delay this change till later in the xdr-encoding
series.
--b.
commit a675223424673a6393fd291280af51fddd6a97ec
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date: Wed Apr 9 11:07:01 2014 -0400
Revert "nfsd4: fix nfs4err_resource in 4.1 case"
Since we're still limiting attributes to a page, the result here is that
a large getattr result will return NFS4ERR_REP_TOO_BIG/TOO_BIG_TO_CACHE
instead of NFS4ERR_RESOURCE.
Both error returns are wrong, and the real bug here is the arbitrary
limit on getattr results, fixed by as-yet out-of-tree patches. But at a
minimum we can make life easier for clients by sticking to one broken
behavior in released kernels instead of two....
Trond says:
one immediate consequence of this patch will be that NFSv4.1
clients will now report EIO instead of EREMOTEIO if they hit the
problem. That may make debugging a little less obvious.
Another consequence will be that if we ever do try to add client
side handling of NFS4ERR_REP_TOO_BIG, then we now have to deal
with the “handle existing buggy server” syndrome.
Reported-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 2723c1b..18881f3 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3627,14 +3627,6 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)
/* nfsd4_check_resp_size guarantees enough room for error status */
if (!op->status)
op->status = nfsd4_check_resp_size(resp, 0);
- if (op->status == nfserr_resource && nfsd4_has_session(&resp->cstate)) {
- struct nfsd4_slot *slot = resp->cstate.slot;
-
- if (slot->sl_flags & NFSD4_SLOT_CACHETHIS)
- op->status = nfserr_rep_too_big_to_cache;
- else
- op->status = nfserr_rep_too_big;
- }
if (so) {
so->so_replay.rp_status = op->status;
so->so_replay.rp_buflen = (char *)resp->p - (char *)(statp+1);
--
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