nfsd: make the server repeat CB_RECALL every couple of seconds

Commit 01ae8969a9ee stopped the NFSv4.1/4.2 server from implicitly
binding the back channel to a new TCP connection so that it
conforms to RFC5661, for NFSv4.1/4.2. An effect of this
for the Linux NFS client is that it will do a
BindConnectionToSession when it sees NFSV4SEQ_CBPATHDOWN
set in a sequence reply. This will fix the back channel, but the
first attempt at a callback like CB_RECALL will already have
failed. Without this patch, a CB_RECALL will not be retried
and that can result in a 5 minute delay until the delegation
times out.

This patch modifies the code so that it will retry the
CB_RECALL every couple of seconds, often avoiding the
5 minute delay.

This is not critical for correct behaviour, but avoids
the 5 minute delay for the case where the Linux client
re-binds the back channel via BindConnectionToSession.

(cherry picked from commit 7a606f280a3e174dcdd12736b7b976903809eb9c)

2 files changed, 16 insertions, 6 deletions

diff --git a/sys/fs/nfs/nfsrvstate.h b/sys/fs/nfs/nfsrvstate.h
index 2d60e8e8141f..427d5b132281 100644
--- a/sys/fs/nfs/nfsrvstate.h
+++ b/sys/fs/nfs/nfsrvstate.h
@@ -220,6 +220,7 @@ struct nfsstate {
 			time_t		expiry;
 			time_t		limit;
 			u_int64_t	compref;
+			time_t		last;
 		} deleg;
 	} ls_un;
 	struct nfslockfile	*ls_lfp;	/* Back pointer */
@@ -238,6 +239,7 @@ struct nfsstate {
 #define	ls_delegtime		ls_un.deleg.expiry
 #define	ls_delegtimelimit	ls_un.deleg.limit
 #define	ls_compref		ls_un.deleg.compref
+#define	ls_lastrecall		ls_un.deleg.last
 
 /*
  * Nfs lock structure.
diff --git a/sys/fs/nfsserver/nfs_nfsdstate.c b/sys/fs/nfsserver/nfs_nfsdstate.c
index 09b637c14e52..5aafebf0dd77 100644
--- a/sys/fs/nfsserver/nfs_nfsdstate.c
+++ b/sys/fs/nfsserver/nfs_nfsdstate.c
@@ -3071,6 +3071,7 @@ tryagain:
 		new_deleg->ls_clp = clp;
 		new_deleg->ls_filerev = filerev;
 		new_deleg->ls_compref = nd->nd_compref;
+		new_deleg->ls_lastrecall = 0;
 		LIST_INSERT_HEAD(&lfp->lf_deleg, new_deleg, ls_file);
 		LIST_INSERT_HEAD(NFSSTATEHASH(clp,
 		    new_deleg->ls_stateid), new_deleg, ls_hash);
@@ -3192,6 +3193,7 @@ tryagain:
 			new_deleg->ls_clp = clp;
 			new_deleg->ls_filerev = filerev;
 			new_deleg->ls_compref = nd->nd_compref;
+			new_deleg->ls_lastrecall = 0;
 			nfsrv_writedelegcnt++;
 			LIST_INSERT_HEAD(&lfp->lf_deleg, new_deleg, ls_file);
 			LIST_INSERT_HEAD(NFSSTATEHASH(clp,
@@ -3262,6 +3264,7 @@ tryagain:
 			new_deleg->ls_clp = clp;
 			new_deleg->ls_filerev = filerev;
 			new_deleg->ls_compref = nd->nd_compref;
+			new_deleg->ls_lastrecall = 0;
 			LIST_INSERT_HEAD(&lfp->lf_deleg, new_deleg, ls_file);
 			LIST_INSERT_HEAD(NFSSTATEHASH(clp,
 			    new_deleg->ls_stateid), new_deleg, ls_hash);
@@ -3340,6 +3343,7 @@ tryagain:
 				new_deleg->ls_clp = clp;
 				new_deleg->ls_filerev = filerev;
 				new_deleg->ls_compref = nd->nd_compref;
+				new_deleg->ls_lastrecall = 0;
 				LIST_INSERT_HEAD(&lfp->lf_deleg, new_deleg,
 				    ls_file);
 				LIST_INSERT_HEAD(NFSSTATEHASH(clp,
@@ -5252,7 +5256,8 @@ nfsrv_delegconflict(struct nfsstate *stp, int *haslockp, NFSPROC_T *p,
 	 * - check to see if the delegation has expired
 	 *   - if so, get the v4root lock and then expire it
 	 */
-	if (!(stp->ls_flags & NFSLCK_DELEGRECALL)) {
+	if ((stp->ls_flags & NFSLCK_DELEGRECALL) == 0 || stp->ls_lastrecall <
+	    time_uptime) {
 		/*
 		 * - do a recall callback, since not yet done
 		 * For now, never allow truncate to be set. To use
@@ -5267,11 +5272,14 @@ nfsrv_delegconflict(struct nfsstate *stp, int *haslockp, NFSPROC_T *p,
 		 * will be extended when ops are done on the delegation
 		 * stateid, up to the timelimit.)
 		 */
-		stp->ls_delegtime = NFSD_MONOSEC + (2 * nfsrv_lease) +
-		    NFSRV_LEASEDELTA;
-		stp->ls_delegtimelimit = NFSD_MONOSEC + (6 * nfsrv_lease) +
-		    NFSRV_LEASEDELTA;
-		stp->ls_flags |= NFSLCK_DELEGRECALL;
+		if ((stp->ls_flags & NFSLCK_DELEGRECALL) == 0) {
+			stp->ls_delegtime = NFSD_MONOSEC + (2 * nfsrv_lease) +
+			    NFSRV_LEASEDELTA;
+			stp->ls_delegtimelimit = NFSD_MONOSEC + (6 *
+			    nfsrv_lease) + NFSRV_LEASEDELTA;
+			stp->ls_flags |= NFSLCK_DELEGRECALL;
+		}
+		stp->ls_lastrecall = time_uptime + 1;
 
 		/*
 		 * Loop NFSRV_CBRETRYCNT times while the CBRecall replies