[RFC PATCH 5 4/7] nfs - cache_lib use service thread if not executing in init namespace

[Ian Kent <raven@themaw.net>]

From: Ian Kent <ikent@redhat.com>

If pipefs is registered within a container pipefs requests should be run
within their originating container also. To do that get a token to a
service thread created within the container environment for usermode
helper calls.

Signed-off-by: Ian Kent <ikent@redhat.com>
Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Oleg Nesterov <onestero@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jeff Layton <jeff.layton@primarydata.com>
---
 fs/nfs/cache_lib.c           |    7 ++++++-
 include/linux/sunrpc/cache.h |    2 ++
 net/sunrpc/cache.c           |    5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/cache_lib.c b/fs/nfs/cache_lib.c
index 5f7b053..78f9b6e 100644
--- a/fs/nfs/cache_lib.c
+++ b/fs/nfs/cache_lib.c
@@ -48,7 +48,12 @@ int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
 
 	if (nfs_cache_getent_prog[0] == '\0')
 		goto out;
-	ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+	if (cd->u.pipefs.umh_token) {
+		int token = cd->u.pipefs.umh_token;
+		ret = call_usermodehelper_service(argv[0], argv, envp,
+						  token, UMH_WAIT_EXEC);
+	} else
+		ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 	/*
 	 * Disable the upcall mechanism if we're getting an ENOENT or
 	 * EACCES error. The admin can re-enable it on the fly by using
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 437ddb6..bb57c7e 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -68,6 +68,8 @@ struct cache_detail_procfs {
 
 struct cache_detail_pipefs {
 	struct dentry *dir;
+	/* Namespace token */
+	int umh_token;
 };
 
 struct cache_detail {
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 5199bb1..eabc0d0 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1811,6 +1811,9 @@ int sunrpc_cache_register_pipefs(struct dentry *parent,
 	if (IS_ERR(dir))
 		return PTR_ERR(dir);
 	cd->u.pipefs.dir = dir;
+	if (cd->net != &init_net)
+		cd->u.pipefs.umh_token =
+			 umh_wq_get_token(cd->u.pipefs.umh_token, "pipefs");
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_register_pipefs);
@@ -1819,6 +1822,8 @@ void sunrpc_cache_unregister_pipefs(struct cache_detail *cd)
 {
 	rpc_remove_cache_dir(cd->u.pipefs.dir);
 	cd->u.pipefs.dir = NULL;
+	umh_wq_put_token(cd->u.pipefs.umh_token);
+	cd->u.pipefs.umh_token = 0;
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_unregister_pipefs);