Re: [PATCH v7 04/11] readahead: allocate folios with mapping_min_order in readahead

Pankaj Raghav (Samsung)
2024-06-21T12:19:19Z

On Tue, Jun 18, 2024 at 08:56:53AM +0200, Hannes Reinecke wrote:
> On 6/17/24 18:39, Pankaj Raghav (Samsung) wrote:
> > On Mon, Jun 17, 2024 at 05:10:15PM +0100, Matthew Wilcox wrote:
> > > On Mon, Jun 17, 2024 at 04:04:20PM +0000, Pankaj Raghav (Samsung) wrote:
> > > > On Mon, Jun 17, 2024 at 01:32:42PM +0100, Matthew Wilcox wrote:
> > > > So the following can still be there from Hannes patch as we have a
> > > > stable reference:
> > > >
> > > > ractl->_workingset |= folio_test_workingset(folio);
> > > > - ractl->_nr_pages++;
> > > > + ractl->_nr_pages += folio_nr_pages(folio);
> > > > + i += folio_nr_pages(folio);
> > > > }
> > >
> > > We _can_, but we just allocated it, so we know what size it is already.
> > Yes.
> >
> > > I'm starting to feel that Hannes' patch should be combined with this
> > > one.
> >
> > Fine by me. @Hannes, is that ok with you?
>
> Sure. I was about to re-send my patchset anyway, so feel free to wrap it in.
Is it ok if I add your Co-developed and Signed-off tag?
This is what I have combining your patch with mine and making willy's
changes:

diff --git a/mm/readahead.c b/mm/readahead.c
index 389cd802da63..f56da953c130 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -247,9 +247,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
struct folio *folio = xa_load(&mapping->i_pages, index + i);
int ret;

-
if (folio && !xa_is_value(folio)) {
- long nr_pages = folio_nr_pages(folio);
/*
* Page already present? Kick off the current batch
* of contiguous pages before continuing with the
@@ -259,18 +257,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
* not worth getting one just for that.
*/
read_pages(ractl);
-
- /*
- * Move the ractl->_index by at least min_pages
- * if the folio got truncated to respect the
- * alignment constraint in the page cache.
- *
- */
- if (mapping != folio->mapping)
- nr_pages = min_nrpages;
-
- VM_BUG_ON_FOLIO(nr_pages < min_nrpages, folio);
- ractl->_index += nr_pages;
+ ractl->_index += min_nrpages;
i = ractl->_index + ractl->_nr_pages - index;
continue;
}
@@ -293,8 +280,8 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
if (i == mark)
folio_set_readahead(folio);
ractl->_workingset |= folio_test_workingset(folio);
- ractl->_nr_pages += folio_nr_pages(folio);
- i += folio_nr_pages(folio);
+ ractl->_nr_pages += min_nrpages;
+ i += min_nrpages;
}

/*