fs: file_remove_privs_flags()

Rename and export __file_remove_privs(); for a buffered write path that
doesn't take the inode lock we need to be able to check if the operation
needs to do work first.

Signed-off-by: Kent Overstreet <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Christian Brauner <[e-mail]>

fs/inode.c

···
 	return notify_change(idmap, dentry, &newattrs, NULL);
 }
 
-static int __file_remove_privs(struct file *file, unsigned int flags)
+int file_remove_privs_flags(struct file *file, unsigned int flags)
 {
 	struct dentry *dentry = file_dentry(file);
 	struct inode *inode = file_inode(file);
···
 		inode_has_no_xattr(inode);
 	return error;
 }
+EXPORT_SYMBOL_GPL(file_remove_privs_flags);
 
 /**
  * file_remove_privs - remove special file privileges (suid, capabilities)
···
  */
 int file_remove_privs(struct file *file)
 {
-	return __file_remove_privs(file, 0);
+	return file_remove_privs_flags(file, 0);
 }
 EXPORT_SYMBOL(file_remove_privs);
 
···
 	 * Clear the security bits if the process is not being run by root.
 	 * This keeps people from modifying setuid and setgid binaries.
 	 */
-	ret = __file_remove_privs(file, flags);
+	ret = file_remove_privs_flags(file, flags);
 	if (ret)
 		return ret;
 

include/linux/fs.h

···
 extern struct inode *new_inode(struct super_block *sb);
 extern void free_inode_nonrcu(struct inode *inode);
 extern int setattr_should_drop_suidgid(struct mnt_idmap *, struct inode *);
+extern int file_remove_privs_flags(struct file *file, unsigned int flags);
 extern int file_remove_privs(struct file *);
 int setattr_should_drop_sgid(struct mnt_idmap *idmap,
 			     const struct inode *inode);