Re: [PATCH v3] zram: support REQ_DISCARD

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 13 Mar 2014 11:46:17 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:

> +	while (n >= PAGE_SIZE) {
> +		/*
> +		 * discard request can be too large so that the zram can
> +		 * be stucked for a long time if we handle the request
> +		 * at once. So handle the request by PAGE_SIZE unit at a time.
> +		 */
> +		write_lock(&zram->meta->tb_lock);
> +		zram_free_page(zram, index);
> +		write_unlock(&zram->meta->tb_lock);
> +		index++;
> +		n -= PAGE_SIZE;
> +	}

Well, you could use something like

	if (need_resched()) {
		unlock()
		schedule()
		lock()
	}

here, or free 100 pages at a time or something silly like that.  I
guess we retain these as options if/when that lock turns out to be
contended.