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

[Pankaj Raghav <pankydev8@gmail.com>]

On Wed, May 25, 2022 at 07:37:45AM -0600, Keith Busch wrote:
> 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:
> > > On Tue, May 24, 2022 at 04:17:54PM +0200, Pankaj Raghav wrote:
> > > > On Mon, May 23, 2022 at 02:01:14PM -0700, Keith Busch wrote:
> > > > > -	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)
Ah. I didn't see the `!=len` part. Sorry for the noise and ignore this
comment.
> 		return -EINVAL;

-- 
Pankaj Raghav