Re: [PATCH] fs/pipe: Fix lockdep false-positive in watchqueue pipe_write()

[David Howells]

Jann Horn <jannh@xxxxxxxxxx> wrote:

> +	/*
> +	 * Reject writing to watch queue pipes before the point where we lock
> +	 * the pipe.
> +	 * Otherwise, lockdep would be unhappy if the caller already has another
> +	 * pipe locked.
> +	 * If we had to support locking a normal pipe and a notification pipe at
> +	 * the same time, we could set up lockdep annotations for that, but
> +	 * since we don't actually need that, it's simpler to just bail here.
> +	 */
> +	if (pipe_has_watch_queue(pipe))
> +		return -EXDEV;
> +

Linus wanted it to be possible for the user to write to a notificaiton pipe.

David