Re: NLM lock reclaim failure

[Marc Eshel <eshel@almaden.ibm.com>]

Hi Trond,
Attached is a tested patch for the bug I posted in the following mail
Marc.

nfs-bounces@lists.sourceforge.net wrote on 10/11/2006 04:28:16 PM:

 > I see an NLM lock reclaim failure (using 2.6.17). Let me describe
 > the simple case first.
 >
 > 1. Client gets an NLM lock
 > 2. Server reboots
 > 3. Client sends lock reclaim request
 > 4. On server, nlm_open() gets return code nfserr_dropit; error gets
 >    converted to nlm_lck_denied by nlm_lookup_file().
 > 5. Client gets status=1, the lock reclaim failed
 >
 > This happens _only_ when the first call to nfsd (fh_verify -> exp_find)
 > comes from lockd trying to find the file. Subsequent calls seem to work.
 >
 > nlm_lookup_file() -> nlm_fopen() -> nfsd_open() -> fh_verify() ->
 > exp_find() returns nfserr_dropit
 >
 > This problem may be related to the following commit to lockd (Trond's
 > tree):
 > commit: 26bcbf965f857c710adafd16cf424f043006b5dd
 > lockd: stop abusing file_lock_list
 >
 > The client earlier retained the list of outstanding locks regardless of
 > reclaim return code. The change above removes all locks from the list
 > and only adds them back after a successful reclaim. Since the reclaim
 > fails, it is removed from the list; so the client will not try to
 > reclaim the lock on a second failure.
 >
 > Note that the problem is not on the client side - it seems the server
 > that should drop the rpc when it gets nfserr_dropit error and not
 > convert it to an nlm_lck_denied.
 >
 > It get even more complicated - when the server doesn't respond
 > immediately to the reclaim, client will retry the rpc, on the second
 > reclaim call, the server will grant the lock to the client but since the
 > client already got the nlm_lck_denied from the first call, it has
 > dropped it from it list. So now we have a lock on the server for a
 > client that doesn't know that it holds the lock.
 >
 > Marc.
 >

Index: lockd/svc.c
===================================================================
RCS file: /cvs/nfsv4/cvs/pnfs/fs/lockd/svc.c,v
retrieving revision 1.1.1.4
diff -u -r1.1.1.4 svc.c
--- lockd/svc.c	12 Jul 2006 19:53:39 -0000	1.1.1.4
+++ lockd/svc.c	13 Oct 2006 04:03:13 -0000
@@ -34,6 +34,7 @@
 #include <linux/sunrpc/svcsock.h>
 #include <linux/lockd/lockd.h>
 #include <linux/nfs.h>
+#include <linux/nfsd/nfsd.h>
 
 #define NLMDBG_FACILITY		NLMDBG_SVC
 #define LOCKD_BUFSIZE		(1024 + NLMSVC_XDRSIZE)
@@ -320,6 +321,43 @@
 }
 EXPORT_SYMBOL(lockd_down);
 
+int
+nlmsvc_dispatch(struct svc_rqst *rqstp, u32 *statp)
+{
+	struct svc_procedure	*procp;
+	kxdrproc_t		xdr;
+	struct kvec *		argv = &rqstp->rq_arg.head[0];
+	struct kvec *		resv = &rqstp->rq_res.head[0];
+
+	dprintk("lockd: nlmsvc_dispatch vers %d proc %d\n",
+				rqstp->rq_vers, rqstp->rq_proc);
+
+	procp = rqstp->rq_procinfo;
+
+	/* Decode arguments */
+	xdr = procp->pc_decode;
+
+	if (xdr && !xdr(rqstp, argv->iov_base, rqstp->rq_argp)) {
+		dprintk("lockd: failed to decode arguments!\n");
+		*statp = rpc_garbage_args;
+		return 1;
+	}
+	/* Now call the procedure handler, and encode status. */
+	*statp = procp->pc_func(rqstp, rqstp->rq_argp, rqstp->rq_resp);
+	if (((struct nlm_res  *)(rqstp->rq_resp))->status == nfserr_dropit) {
+		dprintk("lockd: dropping request!\n");
+		return 0;
+	}
+	/* Encode reply */
+	if (*statp == rpc_success && (xdr = procp->pc_encode)
+	    && !xdr(rqstp, resv->iov_base+resv->iov_len, rqstp->rq_resp)) {
+			dprintk("lockd: failed to encode reply\n");
+			/* serv->sv_stats->rpcsystemerr++; */
+			*statp = rpc_system_err;
+	}
+	return 1;
+}
+
 /*
  * Sysctl parameters (same as module parameters, different interface).
  */
@@ -484,12 +522,14 @@
 		.vs_vers	= 1,
 		.vs_nproc	= 17,
 		.vs_proc	= nlmsvc_procedures,
+		.vs_dispatch	= nlmsvc_dispatch,
 		.vs_xdrsize	= NLMSVC_XDRSIZE,
 };
 static struct svc_version	nlmsvc_version3 = {
 		.vs_vers	= 3,
 		.vs_nproc	= 24,
 		.vs_proc	= nlmsvc_procedures,
+		.vs_dispatch	= nlmsvc_dispatch,
 		.vs_xdrsize	= NLMSVC_XDRSIZE,
 };
 #ifdef CONFIG_LOCKD_V4
@@ -497,6 +537,7 @@
 		.vs_vers	= 4,
 		.vs_nproc	= 24,
 		.vs_proc	= nlmsvc_procedures4,
+		.vs_dispatch	= nlmsvc_dispatch,
 		.vs_xdrsize	= NLMSVC_XDRSIZE,
 };
 #endif
Index: lockd/svcsubs.c
===================================================================
RCS file: /cvs/nfsv4/cvs/pnfs/fs/lockd/svcsubs.c,v
retrieving revision 1.1.1.4
diff -u -r1.1.1.4 svcsubs.c
--- lockd/svcsubs.c	12 Jul 2006 19:53:39 -0000	1.1.1.4
+++ lockd/svcsubs.c	13 Oct 2006 04:03:13 -0000
@@ -16,6 +16,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/nfsd/nfsfh.h>
 #include <linux/nfsd/export.h>
+#include <linux/nfsd/nfsd.h>
 #include <linux/lockd/lockd.h>
 #include <linux/lockd/share.h>
 #include <linux/lockd/sm_inter.h>
@@ -136,12 +137,14 @@
 
 out_free:
 	kfree(file);
+	if (nfserr != nfserr_dropit) {
 #ifdef CONFIG_LOCKD_V4
-	if (nfserr == 1)
-		nfserr = nlm4_stale_fh;
-	else
+		if (nfserr == 1)
+			nfserr = nlm4_stale_fh;
+		else
 #endif
-	nfserr = nlm_lck_denied;
+		nfserr = nlm_lck_denied;
+	}
 	goto out_unlock;
 }
 
Index: nfsd/lockd.c
===================================================================
RCS file: /cvs/nfsv4/cvs/pnfs/fs/nfsd/lockd.c,v
retrieving revision 1.1.1.3
diff -u -r1.1.1.3 lockd.c
--- nfsd/lockd.c	4 Apr 2006 17:55:25 -0000	1.1.1.3
+++ nfsd/lockd.c	13 Oct 2006 04:03:14 -0000
@@ -49,6 +49,8 @@
 		return 0;
 	case nfserr_stale:
 		return 1;
+	case nfserr_dropit:
+		return nfserr;
 	default:
 		return 2;
 	}



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