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>

1 files changed, 12 insertions, 2 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,