linux-kernel - Re: [PATCH v3 04/11] readahead: rework loop in page_cache_ra

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Message-ID: <k3pqp6aryvnekneqqs7hnolr7pkdayrudpjpizpptot6jp7xax@cog4esp24yve>
Date: Tue, 26 Mar 2024 16:11:33 +0100
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	gost.dev@...sung.com, chandan.babu@...cle.com, hare@...e.de, mcgrof@...nel.org, 
	djwong@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	david@...morbit.com, akpm@...ux-foundation.org, Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [PATCH v3 04/11] readahead: rework loop in
 page_cache_ra_unbounded()

On Mon, Mar 25, 2024 at 06:41:01PM +0000, Matthew Wilcox wrote:
> On Wed, Mar 13, 2024 at 06:02:46PM +0100, Pankaj Raghav (Samsung) wrote:
> > @@ -239,8 +239,8 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> >  			 * not worth getting one just for that.
> >  			 */
> >  			read_pages(ractl);
> > -			ractl->_index++;
> > -			i = ractl->_index + ractl->_nr_pages - index - 1;
> > +			ractl->_index += folio_nr_pages(folio);
> > +			i = ractl->_index + ractl->_nr_pages - index;
> >  			continue;
> >  		}
> >  
> > @@ -252,13 +252,14 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> >  			folio_put(folio);
> >  			read_pages(ractl);
> >  			ractl->_index++;
> > -			i = ractl->_index + ractl->_nr_pages - index - 1;
> > +			i = ractl->_index + ractl->_nr_pages - index;
> >  			continue;
> >  		}
> 
> You changed index++ in the first hunk, but not the second hunk.  Is that
> intentional?
After having some back and forth with Hannes, I see where the confusion
is coming from.

I intended this to be a non-functional change that helps with adding 
min_order support later.

As this is a non-functional change, I will move this patch to be at the
start of the series as preparation patches before we start adding min_order
helpers and support.

--
Pankaj