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>

6 files changed, 72 insertions, 18 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,
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 3d1fad22185a..23ee25981a0c 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -70,9 +70,9 @@ struct cache_detail {
         char                    *name;
         void                    (*cache_put)(struct kref *);
 
-        void                    (*cache_request)(struct cache_detail *cd,
-                                                 struct cache_head *h,
-                                                 char **bpp, int *blen);
+        int                     (*cache_upcall)(struct cache_detail *,
+                                                struct cache_head *);
+
         int                     (*cache_parse)(struct cache_detail *,
                                                char *buf, int len);
 
@@ -135,6 +135,13 @@ extern struct cache_head *
 sunrpc_cache_update(struct cache_detail *detail,
                     struct cache_head *new, struct cache_head *old, int hash);
 
+extern int
+sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
+                void (*cache_request)(struct cache_detail *,
+                                      struct cache_head *,
+                                      char **,
+                                      int *));
+
 
 extern void cache_clean_deferred(void *owner);
 
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 2278a50c6444..2e6a148d277c 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -181,6 +181,11 @@ static void rsi_request(struct cache_detail *cd,
         (*bpp)[-1] = '\n';
 }
 
+static int rsi_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+        return sunrpc_cache_pipe_upcall(cd, h, rsi_request);
+}
+
 
 static int rsi_parse(struct cache_detail *cd,
                     char *mesg, int mlen)
@@ -270,7 +275,7 @@ static struct cache_detail rsi_cache = {
         .hash_table     = rsi_table,
         .name           = "auth.rpcsec.init",
         .cache_put      = rsi_put,
-        .cache_request  = rsi_request,
+        .cache_upcall   = rsi_upcall,
         .cache_parse    = rsi_parse,
         .match          = rsi_match,
         .init           = rsi_init,
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index c8e7d2d07260..e438352bed7b 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -176,7 +176,13 @@ struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_update);
 
-static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h);
+static int cache_make_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+        if (!cd->cache_upcall)
+                return -EINVAL;
+        return cd->cache_upcall(cd, h);
+}
+
 /*
  * This is the generic cache management routine for all
  * the authentication caches.
@@ -322,7 +328,7 @@ static int create_cache_proc_entries(struct cache_detail *cd)
         if (p == NULL)
                 goto out_nomem;
 
-        if (cd->cache_request || cd->cache_parse) {
+        if (cd->cache_upcall || cd->cache_parse) {
                 p = proc_create_data("channel", S_IFREG|S_IRUSR|S_IWUSR,
                                      cd->proc_ent, &cache_file_operations, cd);
                 cd->channel_ent = p;
@@ -1080,10 +1086,16 @@ static void warn_no_listener(struct cache_detail *detail)
 }
 
 /*
- * register an upcall request to user-space.
+ * register an upcall request to user-space and queue it up for read() by the
+ * upcall daemon.
+ *
  * Each request is at most one page long.
  */
-static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h)
+int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
+                void (*cache_request)(struct cache_detail *,
+                                      struct cache_head *,
+                                      char **,
+                                      int *))
 {
 
         char *buf;
@@ -1091,9 +1103,6 @@ static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h)
         char *bp;
         int len;
 
-        if (detail->cache_request == NULL)
-                return -EINVAL;
-
         if (atomic_read(&detail->readers) == 0 &&
             detail->last_close < get_seconds() - 30) {
                         warn_no_listener(detail);
@@ -1112,7 +1121,7 @@ static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h)
 
         bp = buf; len = PAGE_SIZE;
 
-        detail->cache_request(detail, h, &bp, &len);
+        cache_request(detail, h, &bp, &len);
 
         if (len < 0) {
                 kfree(buf);
@@ -1130,6 +1139,7 @@ static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h)
         wake_up(&queue_wait);
         return 0;
 }
+EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall);
 
 /*
  * parse a message from user-space and pass it
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 5c865e2d299e..6caffa34ac01 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -171,6 +171,11 @@ static void ip_map_request(struct cache_detail *cd,
         (*bpp)[-1] = '\n';
 }
 
+static int ip_map_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+        return sunrpc_cache_pipe_upcall(cd, h, ip_map_request);
+}
+
 static struct ip_map *ip_map_lookup(char *class, struct in6_addr *addr);
 static int ip_map_update(struct ip_map *ipm, struct unix_domain *udom, time_t expiry);
 
@@ -289,7 +294,7 @@ struct cache_detail ip_map_cache = {
         .hash_table     = ip_table,
         .name           = "auth.unix.ip",
         .cache_put      = ip_map_put,
-        .cache_request  = ip_map_request,
+        .cache_upcall   = ip_map_upcall,
         .cache_parse    = ip_map_parse,
         .cache_show     = ip_map_show,
         .match          = ip_map_match,
@@ -523,6 +528,11 @@ static void unix_gid_request(struct cache_detail *cd,
         (*bpp)[-1] = '\n';
 }
 
+static int unix_gid_upcall(struct cache_detail *cd, struct cache_head *h)
+{
+        return sunrpc_cache_pipe_upcall(cd, h, unix_gid_request);
+}
+
 static struct unix_gid *unix_gid_lookup(uid_t uid);
 extern struct cache_detail unix_gid_cache;
 
@@ -622,7 +632,7 @@ struct cache_detail unix_gid_cache = {
         .hash_table     = gid_table,
         .name           = "auth.unix.gid",
         .cache_put      = unix_gid_put,
-        .cache_request  = unix_gid_request,
+        .cache_upcall   = unix_gid_upcall,
         .cache_parse    = unix_gid_parse,
         .cache_show     = unix_gid_show,
         .match          = unix_gid_match,