Patch-mainline: submitted 04aug2009
References: bnc#498708
From: NeilBrown <neilb@suse.de>
Date: Tue, 4 Aug 2009 15:06:38 +1000
Subject: [PATCH 08/12] sunrpc/cache: retry cache lookups that return -ETIMEDOUT

If cache_check returns -ETIMEDOUT, then the cache item is not
up-to-date, but there is no pending upcall.
This could mean the data is not available, or it could mean that the
good data has been stored in a new cache item.

So re-do the lookup and if that returns a new item, proceed using that
item.

Signed-off-by: NeilBrown <neilb@suse.de>

---
 fs/nfsd/export.c          |   18 ++++++++++++++++++
 net/sunrpc/svcauth_unix.c |   23 ++++++++++++++++++++---
 2 files changed, 38 insertions(+), 3 deletions(-)

--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -794,9 +794,18 @@ exp_find_key(svc_client *clp, int fsid_t
 	memcpy(key.ek_fsid, fsidv, key_len(fsid_type));
 
 	ek = svc_expkey_lookup(&key);
+ again:
 	if (ek == NULL)
 		return ERR_PTR(-ENOMEM);
 	err = cache_check(&svc_expkey_cache, &ek->h, reqp);
+	if (err == -ETIMEDOUT) {
+		struct svc_expkey *prev_ek = ek;
+		ek = svc_expkey_lookup(&key);
+		if (ek != prev_ek)
+			goto again;
+		if (ek)
+			cache_put(&ek->h, &svc_expkey_cache);
+	}
 	if (err)
 		return ERR_PTR(err);
 	return ek;
@@ -866,9 +875,18 @@ static svc_export *exp_get_by_name(svc_c
 	key.ex_path = *path;
 
 	exp = svc_export_lookup(&key);
+ retry:
 	if (exp == NULL)
 		return ERR_PTR(-ENOMEM);
 	err = cache_check(&svc_export_cache, &exp->h, reqp);
+	if (err == -ETIMEDOUT) {
+		struct svc_export *prev_exp = exp;
+		exp = svc_export_lookup(&key);
+		if (exp != prev_exp)
+			goto retry;
+		if (exp)
+			cache_put(&exp->h, &svc_export_cache);
+	}
 	if (err)
 		return ERR_PTR(err);
 	return exp;
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -663,13 +663,14 @@ static struct unix_gid *unix_gid_lookup(
 
 static struct group_info *unix_gid_find(uid_t uid, struct svc_rqst *rqstp)
 {
-	struct unix_gid *ug;
+	struct unix_gid *ug, *prevug;
 	struct group_info *gi;
 	int ret;
 
 	ug = unix_gid_lookup(uid);
 	if (!ug)
 		return ERR_PTR(-EAGAIN);
+retry:
 	ret = cache_check(&unix_gid_cache, &ug->h, &rqstp->rq_chandle);
 	switch (ret) {
 	case -ENOENT:
@@ -678,6 +679,13 @@ static struct group_info *unix_gid_find(
 		gi = get_group_info(ug->gi);
 		cache_put(&ug->h, &unix_gid_cache);
 		return gi;
+	case -ETIMEDOUT:
+		prevug = ug;
+		ug = unix_gid_lookup(uid);
+		if (ug != prevug)
+			goto retry;
+		if (ug)
+			cache_put(&ug->h, &unix_gid_cache);
 	default:
 		return ERR_PTR(-EAGAIN);
 	}
@@ -688,7 +696,7 @@ svcauth_unix_set_client(struct svc_rqst
 {
 	struct sockaddr_in *sin;
 	struct sockaddr_in6 *sin6, sin6_storage;
-	struct ip_map *ipm;
+	struct ip_map *ipm, *prev_ipm;
 	struct group_info *gi;
 	struct svc_cred *cred = &rqstp->rq_cred;
 
@@ -714,14 +722,23 @@ svcauth_unix_set_client(struct svc_rqst
 		ipm = ip_map_lookup(rqstp->rq_server->sv_program->pg_class,
 				    &sin6->sin6_addr);
 
+ retry:
 	if (ipm == NULL)
 		return SVC_DENIED;
 
 	switch (cache_check(&ip_map_cache, &ipm->h, &rqstp->rq_chandle)) {
 		default:
 			BUG();
-		case -EAGAIN:
 		case -ETIMEDOUT:
+			prev_ipm = ipm;
+			ipm = ip_map_lookup(rqstp->rq_server->sv_program->pg_class,
+					    &sin6->sin6_addr);
+			if (ipm != prev_ipm)
+				goto retry;
+			if (ipm)
+				cache_put(&ipm->h, &ip_map_cache);
+
+		case -EAGAIN:
 			return SVC_DROP;
 		case -ENOENT:
 			return SVC_DENIED;