SUNRPC: Allow the cache_detail to specify alternative upcall mechanisms

For events that are rare, such as referral DNS lookups, it makes limited
sense to have a daemon constantly listening for upcalls on a channel. An
alternative in those cases might simply be to run the app that fills the
cache using call_usermodehelper_exec() and friends.

The following patch allows the cache_detail to specify alternative upcall
mechanisms for these particular cases.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 26 insertions, 4 deletions

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index b92a27629fb7..d9462643155c 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -85,6 +85,11 @@ static void expkey_request(struct cache_detail *cd,
 	(*bpp)[-1] = '\n';
 }
 
+static int expkey_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+	return sunrpc_cache_pipe_upcall(cd, h, expkey_request);
+}
+
 static struct svc_expkey *svc_expkey_update(struct svc_expkey *new, struct svc_expkey *old);
 static struct svc_expkey *svc_expkey_lookup(struct svc_expkey *);
 static struct cache_detail svc_expkey_cache;
@@ -259,7 +264,7 @@ static struct cache_detail svc_expkey_cache = {
 	.hash_table	= expkey_table,
 	.name		= "nfsd.fh",
 	.cache_put	= expkey_put,
-	.cache_request	= expkey_request,
+	.cache_upcall	= expkey_upcall,
 	.cache_parse	= expkey_parse,
 	.cache_show	= expkey_show,
 	.match		= expkey_match,
@@ -355,6 +360,11 @@ static void svc_export_request(struct cache_detail *cd,
 	(*bpp)[-1] = '\n';
 }
 
+static int svc_export_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+	return sunrpc_cache_pipe_upcall(cd, h, svc_export_request);
+}
+
 static struct svc_export *svc_export_update(struct svc_export *new,
 					    struct svc_export *old);
 static struct svc_export *svc_export_lookup(struct svc_export *);
@@ -724,7 +734,7 @@ struct cache_detail svc_export_cache = {
 	.hash_table	= export_table,
 	.name		= "nfsd.export",
 	.cache_put	= svc_export_put,
-	.cache_request	= svc_export_request,
+	.cache_upcall	= svc_export_upcall,
 	.cache_parse	= svc_export_parse,
 	.cache_show	= svc_export_show,
 	.match		= svc_export_match,
diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index e9012ad36ac0..cdfa86fa1471 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -146,6 +146,12 @@ idtoname_request(struct cache_detail *cd, struct cache_head *ch, char **bpp,
 }
 
 static int
+idtoname_upcall(struct cache_detail *cd, struct cache_head *ch)
+{
+	return sunrpc_cache_pipe_upcall(cd, ch, idtoname_request);
+}
+
+static int
 idtoname_match(struct cache_head *ca, struct cache_head *cb)
 {
 	struct ent *a = container_of(ca, struct ent, h);
@@ -192,7 +198,7 @@ static struct cache_detail idtoname_cache = {
 	.hash_table	= idtoname_table,
 	.name		= "nfs4.idtoname",
 	.cache_put	= ent_put,
-	.cache_request	= idtoname_request,
+	.cache_upcall	= idtoname_upcall,
 	.cache_parse	= idtoname_parse,
 	.cache_show	= idtoname_show,
 	.warn_no_listener = warn_no_idmapd,
@@ -325,6 +331,12 @@ nametoid_request(struct cache_detail *cd, struct cache_head *ch, char **bpp,
 }
 
 static int
+nametoid_upcall(struct cache_detail *cd, struct cache_head *ch)
+{
+	return sunrpc_cache_pipe_upcall(cd, ch, nametoid_request);
+}
+
+static int
 nametoid_match(struct cache_head *ca, struct cache_head *cb)
 {
 	struct ent *a = container_of(ca, struct ent, h);
@@ -363,7 +375,7 @@ static struct cache_detail nametoid_cache = {
 	.hash_table	= nametoid_table,
 	.name		= "nfs4.nametoid",
 	.cache_put	= ent_put,
-	.cache_request	= nametoid_request,
+	.cache_upcall	= nametoid_upcall,
 	.cache_parse	= nametoid_parse,
 	.cache_show	= nametoid_show,
 	.warn_no_listener = warn_no_idmapd,