VFS: Add GPL_EXPORTED function vfs_kern_mount()

do_kern_mount() does not allow the kernel to use private mount interfaces
without exposing the same interfaces to userland. The problem is that the
filesystem is referenced by name, thus meaning that it and its mount
interface must be registered in the global filesystem list.

vfs_kern_mount() passes the struct file_system_type as an explicit
parameter in order to overcome this limitation.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/super.c b/fs/super.c
index a66f66bb804979a62cf6233473bdeae191884410..848be4fc67a2a608613ff90e0f76dfee7078731b 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -800,17 +800,13 @@ struct super_block *get_sb_single(struct file_system_type *fs_type,
 EXPORT_SYMBOL(get_sb_single);
 
 struct vfsmount *
-do_kern_mount(const char *fstype, int flags, const char *name, void *data)
+vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
 {
-       struct file_system_type *type = get_fs_type(fstype);
        struct super_block *sb = ERR_PTR(-ENOMEM);
        struct vfsmount *mnt;
        int error;
        char *secdata = NULL;
 
-       if (!type)
-               return ERR_PTR(-ENODEV);
-
        mnt = alloc_vfsmnt(name);
        if (!mnt)
                goto out;
@@ -841,7 +837,6 @@ do_kern_mount(const char *fstype, int flags, const char *name, void *data)
        mnt->mnt_parent = mnt;
        up_write(&sb->s_umount);
        free_secdata(secdata);
-       put_filesystem(type);
        return mnt;
 out_sb:
        up_write(&sb->s_umount);
@@ -852,10 +847,23 @@ out_free_secdata:
 out_mnt:
        free_vfsmnt(mnt);
 out:
-       put_filesystem(type);
        return (struct vfsmount *)sb;
 }
 
+EXPORT_SYMBOL_GPL(vfs_kern_mount);
+
+struct vfsmount *
+do_kern_mount(const char *fstype, int flags, const char *name, void *data)
+{
+       struct file_system_type *type = get_fs_type(fstype);
+       struct vfsmount *mnt;
+       if (!type)
+               return ERR_PTR(-ENODEV);
+       mnt = vfs_kern_mount(type, flags, name, data);
+       put_filesystem(type);
+       return mnt;
+}
+
 EXPORT_SYMBOL_GPL(do_kern_mount);
 
 struct vfsmount *kern_mount(struct file_system_type *type)

diff --git a/include/linux/mount.h b/include/linux/mount.h
index b7472ae91fa4a8396e9eaa9a2bedb6c1af916b64..aff68c3660f5e04c27fbb77297218587650cb341 100644 (file)
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -73,6 +73,11 @@ extern struct vfsmount *alloc_vfsmnt(const char *name);
 extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
                                      const char *name, void *data);
 
+struct file_system_type;
+extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
+                                     int flags, const char *name,
+                                     void *data);
+
 struct nameidata;
 
 extern int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,