UBUNTU: ubuntu: overlayfs -- vfs: add i_op->open()

Add a new inode operation i_op->open().  This is for stacked
filesystems that want to return a struct file from a different
filesystem.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andy Whitcroft <apw@canonical.com>

1 files changed, 23 insertions, 2 deletions

diff --git a/fs/open.c b/fs/open.c
index f75e70b1fcf..892c386b852 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -800,7 +800,7 @@ struct file *nameidata_to_filp(struct nameidata *nd)
 
 	/* Has the filesystem initialised the file for us? */
 	if (filp->f_path.dentry == NULL)
-		filp = __dentry_open(&nd->path, filp, NULL, cred);
+		filp = vfs_open(&nd->path, filp, cred);
 
 	return filp;
 }
@@ -825,7 +825,7 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 	f = get_empty_filp();
 	if (f != NULL) {
 		f->f_flags = flags;
-		ret = __dentry_open(&path, f, NULL, cred);
+		ret = vfs_open(&path, f, cred);
 	}
 	path_put(&path);
 
@@ -833,6 +833,27 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 }
 EXPORT_SYMBOL(dentry_open);
 
+/**
+ * vfs_open - open the file at the given path
+ * @path: path to open
+ * @filp: newly allocated file with f_flag initialized
+ * @cred: credentials to use
+ *
+ * Open the file.  If successful, the returned file will have acquired
+ * an additional reference for path.
+ */
+struct file *vfs_open(struct path *path, struct file *filp,
+		      const struct cred *cred)
+{
+	struct inode *inode = path->dentry->d_inode;
+
+	if (inode->i_op->open)
+		return inode->i_op->open(path->dentry, filp, cred);
+	else
+		return __dentry_open(path, filp, NULL, cred);
+}
+EXPORT_SYMBOL(vfs_open);
+
 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 {
 	struct fdtable *fdt = files_fdtable(files);