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Subject[PATCH 4/5] shmem: use call_once()
This patch defers mounting tmpfs till shmem_file_setup() is
called first time by using call_once().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
mm/shmem.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)

Index: 2.6-rc/mm/shmem.c
===================================================================
--- 2.6-rc.orig/mm/shmem.c
+++ 2.6-rc/mm/shmem.c
@@ -50,6 +50,7 @@
#include <linux/migrate.h>
#include <linux/highmem.h>
#include <linux/seq_file.h>
+#include <linux/once.h>

#include <asm/uaccess.h>
#include <asm/div64.h>
@@ -2520,7 +2521,6 @@ static struct file_system_type tmpfs_fs_
.get_sb = shmem_get_sb,
.kill_sb = kill_litter_super,
};
-static struct vfsmount *shm_mnt;

static int __init init_tmpfs(void)
{
@@ -2540,27 +2540,29 @@ static int __init init_tmpfs(void)
goto out2;
}

- shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
- tmpfs_fs_type.name, NULL);
- if (IS_ERR(shm_mnt)) {
- error = PTR_ERR(shm_mnt);
- printk(KERN_ERR "Could not kern_mount tmpfs\n");
- goto out1;
- }
return 0;
-
-out1:
- unregister_filesystem(&tmpfs_fs_type);
out2:
destroy_inodecache();
out3:
bdi_destroy(&shmem_backing_dev_info);
out4:
- shm_mnt = ERR_PTR(error);
return error;
}
module_init(init_tmpfs)

+static struct vfsmount *shm_mnt;
+
+static int init_shm_mnt(void)
+{
+ shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
+ tmpfs_fs_type.name, NULL);
+ if (IS_ERR(shm_mnt)) {
+ printk(KERN_ERR "Could not kern_mount tmpfs\n");
+ return PTR_ERR(shm_mnt);
+ }
+ return 0;
+}
+
/*
* shmem_file_setup - get an unlinked file living in tmpfs
*
@@ -2575,9 +2577,11 @@ struct file *shmem_file_setup(char *name
struct inode *inode;
struct dentry *dentry, *root;
struct qstr this;
+ static DEFINE_ONCE(once);

- if (IS_ERR(shm_mnt))
- return (void *)shm_mnt;
+ error = call_once(&once, init_shm_mnt);
+ if (error)
+ return ERR_PTR(error);

if (size < 0 || size > SHMEM_MAX_BYTES)
return ERR_PTR(-EINVAL);

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