pidfs: make inodes mutable

Prepare for allowing extended attributes to be set on pidfd inodes by
allowing them to be mutable.

Link: https://lore.kernel.org/[e-mail]
Reviewed-by: Alexander Mikhalitsyn <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>

fs/pidfs.c

···
 
 	inode->i_private = data;
 	inode->i_flags |= S_PRIVATE | S_ANON_INODE;
+	/* We allow to set xattrs. */
+	inode->i_flags &= ~S_IMMUTABLE;
 	inode->i_mode |= S_IRWXU;
 	inode->i_op = &pidfs_inode_operations;
 	inode->i_fop = &pidfs_file_operations;