cifs: implement i_op->atomic_open()

Add an ->atomic_open implementation which replaces the atomic lookup+open+create
operation implemented via ->lookup and ->create operations.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Steve French <sfrench@samba.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/cifs/cifsfs.c

@@ -777,6 +777,7 @@ struct file_system_type cifs_fs_type = {
 };
 const struct inode_operations cifs_dir_inode_ops = {
 	.create = cifs_create,
+	.atomic_open = cifs_atomic_open,
 	.lookup = cifs_lookup,
 	.getattr = cifs_getattr,
 	.unlink = cifs_unlink,

fs/cifs/cifsfs.h

@@ -46,6 +46,9 @@ extern const struct inode_operations cifs_dir_inode_ops;
 extern struct inode *cifs_root_iget(struct super_block *);
 extern int cifs_create(struct inode *, struct dentry *, umode_t,
 		       struct nameidata *);
+extern struct file *cifs_atomic_open(struct inode *, struct dentry *,
+				     struct opendata *, unsigned, umode_t,
+				     bool *);
 extern struct dentry *cifs_lookup(struct inode *, struct dentry *,
 				  struct nameidata *);
 extern int cifs_unlink(struct inode *dir, struct dentry *dentry);