Re: [PATCHv3 1/6] block/bio: remove duplicate append pages code

On Wed, May 25, 2022 at 09:49:41AM +0200, Pankaj Raghav wrote:

On Tue, May 24, 2022 at 09:38:32AM -0600, Keith Busch wrote:

quoted

On Tue, May 24, 2022 at 04:17:54PM +0200, Pankaj Raghav wrote:

quoted

On Mon, May 23, 2022 at 02:01:14PM -0700, Keith Busch wrote:

quoted

-	if (WARN_ON_ONCE(!max_append_sectors))
-		return 0;

I don't see this check in the append path. Should it be added in
bio_iov_add_zone_append_page() function?

I'm not sure this check makes a lot of sense. If it just returns 0 here, then
won't that get bio_iov_iter_get_pages() stuck in an infinite loop? The bio
isn't filling, the iov isn't advancing, and 0 indicates keep-going.

Yeah but if max_append_sectors is zero, then bio_add_hw_page() also
returns 0 as follows:
....
	if (((bio->bi_iter.bi_size + len) >> 9) > max_sectors)
		return 0;
....
With WARN_ON_ONCE, we at least get a warning message if it gets stuck in an
infinite loop because of max_append_sectors being zero right?

The return for this function is the added length, not an indicator of success.
And we already handle '0' as an error from bio_iov_add_zone_append_page():

	if (bio_add_hw_page(q, bio, page, len, offset,
			queue_max_zone_append_sectors(q), &same_page) != len)
		return -EINVAL;