Re: [PATCH] files: rcu free files_struct

[Matthew Wilcox]

On Wed, Dec 09, 2020 at 12:04:38PM -0600, Eric W. Biederman wrote:
> @@ -397,8 +397,9 @@ static struct fdtable *close_files(struct files_struct * files)
>  		set = fdt->open_fds[j++];
>  		while (set) {
>  			if (set & 1) {
> -				struct file * file = xchg(&fdt->fd[i], NULL);
> +				struct file * file = fdt->fd[i];
>  				if (file) {
> +					rcu_assign_pointer(fdt->fd[i], NULL);

Assuming this is safe, you can use RCU_INIT_POINTER() here because you're
storing NULL, so you don't need the wmb() before storing the pointer.