[PATCH 3/5] hugetlbfs: use call_once()

[Akinobu Mita <akinobu.mita@gmail.com>]

This patch defers mounting hugetlbfs till hugetlb_file_setup() is
called first time by using call_once().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: William Irwin <wli@holomorphy.com>
---
 fs/hugetlbfs/inode.c |   30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

Index: 2.6-rc/fs/hugetlbfs/inode.c
===================================================================
--- 2.6-rc.orig/fs/hugetlbfs/inode.c
+++ 2.6-rc/fs/hugetlbfs/inode.c
@@ -31,6 +31,7 @@
 #include <linux/dnotify.h>
 #include <linux/statfs.h>
 #include <linux/security.h>
+#include <linux/once.h>
 
 #include <asm/uaccess.h>
 
@@ -903,6 +904,13 @@ static struct file_system_type hugetlbfs
 
 static struct vfsmount *hugetlbfs_vfsmount;
 
+static int init_hugetlbfs_vfsmount(void)
+{
+	hugetlbfs_vfsmount = kern_mount(&hugetlbfs_fs_type);
+
+	return IS_ERR(hugetlbfs_vfsmount) ? PTR_ERR(hugetlbfs_vfsmount) : 0;
+}
+
 static int can_do_hugetlb_shm(void)
 {
 	return likely(capable(CAP_IPC_LOCK) ||
@@ -912,14 +920,16 @@ static int can_do_hugetlb_shm(void)
 
 struct file *hugetlb_file_setup(const char *name, size_t size)
 {
-	int error = -ENOMEM;
+	int error;
 	struct file *file;
 	struct inode *inode;
 	struct dentry *dentry, *root;
 	struct qstr quick_string;
+	static DEFINE_ONCE(once);
 
-	if (!hugetlbfs_vfsmount)
-		return ERR_PTR(-ENOENT);
+	error = call_once(&once, init_hugetlbfs_vfsmount);
+	if (error)
+		return ERR_PTR(error);
 
 	if (!can_do_hugetlb_shm())
 		return ERR_PTR(-EPERM);
@@ -970,7 +980,6 @@ out_shm_unlock:
 static int __init init_hugetlbfs_fs(void)
 {
 	int error;
-	struct vfsmount *vfsmount;
 
 	error = bdi_init(&hugetlbfs_backing_dev_info);
 	if (error)
@@ -986,18 +995,9 @@ static int __init init_hugetlbfs_fs(void
 	if (error)
 		goto out;
 
-	vfsmount = kern_mount(&hugetlbfs_fs_type);
-
-	if (!IS_ERR(vfsmount)) {
-		hugetlbfs_vfsmount = vfsmount;
-		return 0;
-	}
-
-	error = PTR_ERR(vfsmount);
-
+	return 0;
  out:
-	if (error)
-		kmem_cache_destroy(hugetlbfs_inode_cachep);
+	kmem_cache_destroy(hugetlbfs_inode_cachep);
  out2:
 	bdi_destroy(&hugetlbfs_backing_dev_info);
 	return error;