On Fri, 2014-10-24 at 09:34 -0400, Jeff Layton wrote:
> On Fri, 24 Oct 2014 07:26:44 -0400
> Jeff Layton <jlayton@xxxxxxxxxxxxxxx> wrote:
>
> > I guess the theory here is that the client sent the request, and got a
> > TCP ACK and then the server never responded because it dropped the
> > request? That sounds plausible and we almost certainly want something
> > like the above for v4.0.
> >
> > If the above patch fixes Christoph's problem with v4.1 though, then I
> > think we'll need more investigation into why. I don't see a way to get
> > a dropped request with v4.1. Those mainly occur due to interaction with
> > the DRC (disabled for v4.1) or with svc_defer (disabled for all v4
> > requests).
> >
> > Is it possible that one of the nfsd threads is just hung while
> > processing an RPC and that's why you're not getting a response?
> >
>
> Ok, I'm able to reproduce this too and got a network trace. I think
> Trond is correct as to the cause:
>
> I see a SETATTR call go out and then see a TCP ACK for it a little
> later, but didn't see a reply sent for it.
>
> I sprinkled in some printks around the "dropit" codepath above and in
> some other areas however and none of them fired. So while Trond's patch
> looks like it might be correct, I don't think it'll fix the problem I'm
> seeing.
>
> Sniffing a little later, it seems like the server replies are being
> delayed somehow:
You can get deferrals in the authentication code which trigger drops.
Here is a variant which tries to deal with that:
8<-----------------------------------------------------
>From a9be1292152af2cb651415c44fd3d91b3d017240 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Date: Fri, 24 Oct 2014 12:54:47 +0300
Subject: [PATCH v2] nfsd: Ensure that NFSv4 always drops the connection when
dropping a request
Both RFC3530 and RFC5661 impose a requirement on the server that it MUST NOT
drop a request unless the connection is broken. This is in order to allow
clients to assume that they can always expect an answer unless the
connection is broken.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
v2: Also deal with NFSv4 requests dropped due to authentication issues
fs/nfsd/nfs4proc.c | 6 ++++++
include/linux/sunrpc/svc.h | 1 +
net/sunrpc/svc.c | 13 +++++++++----
3 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index cdeb3cfd6f32..500ac76662a8 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1960,6 +1960,11 @@ static const char *nfsd4_op_name(unsigned opnum)
return "unknown_operation";
}
+static void nfsd4_dropme(struct svc_rqst *rqstp)
+{
+ svc_close_xprt(rqstp->rq_xprt);
+}
+
#define nfsd4_voidres nfsd4_voidargs
struct nfsd4_voidargs { int dummy; };
@@ -1989,6 +1994,7 @@ struct svc_version nfsd_version4 = {
.vs_nproc = 2,
.vs_proc = nfsd_procedures4,
.vs_dispatch = nfsd_dispatch,
+ .vs_dropme = nfsd4_dropme,
.vs_xdrsize = NFS4_SVC_XDRSIZE,
.vs_rpcb_optnl = 1,
};
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 21678464883a..824656da1f6d 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -400,6 +400,7 @@ struct svc_version {
* vs_dispatch == NULL means use default dispatcher.
*/
int (*vs_dispatch)(struct svc_rqst *, __be32 *);
+ void (*vs_dropme)(struct svc_rqst *);
};
/*
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index ca8a7958f4e6..a178496ce2c1 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1111,9 +1111,13 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
rqstp->rq_vers = vers = svc_getnl(argv); /* version number */
rqstp->rq_proc = proc = svc_getnl(argv); /* procedure number */
- for (progp = serv->sv_program; progp; progp = progp->pg_next)
- if (prog == progp->pg_prog)
+ for (progp = serv->sv_program; progp; progp = progp->pg_next) {
+ if (prog == progp->pg_prog) {
+ if (vers < progp->pg_nvers)
+ versp = progp->pg_vers[vers];
break;
+ }
+ }
/*
* Decode auth data, and add verifier to reply buffer.
@@ -1148,8 +1152,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
if (progp == NULL)
goto err_bad_prog;
- if (vers >= progp->pg_nvers ||
- !(versp = progp->pg_vers[vers]))
+ if (versp == NULL)
goto err_bad_vers;
procp = versp->vs_proc + proc;
@@ -1228,6 +1231,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
dropit:
svc_authorise(rqstp); /* doesn't hurt to call this twice */
dprintk("svc: svc_process dropit\n");
+ if (versp && versp->vs_dropme)
+ versp->vs_dropme(rqstp);
return 0;
err_short_len:
--
1.9.3
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