Re: [PATCH v5 09/23] cifs: Convert wdata_alloc_and_fillpages() to use filemap_get_folios_tag()

[Tom Talpey]

This code would be a lot more readable if it had fewer goto's.
The goto out's are ok but the again and add_more are easily
eliminated.

Two possibilities...

On 1/12/2023 12:19 PM, Vishal Moola wrote:
> On Wed, Jan 4, 2023 at 1:15 PM Vishal Moola (Oracle)
> <vishal.moola@xxxxxxxxx> wrote:
> > This is in preparation for the removal of find_get_pages_range_tag(). Now also
> > supports the use of large folios.
> >
> > Since tofind might be larger than the max number of folios in a
> > folio_batch (15), we loop through filling in wdata->pages pulling more
> > batches until we either reach tofind pages or run out of folios.
> >
> > This function may not return all pages in the last found folio before
> > tofind pages are reached.
> >
> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
> > ---
> >   fs/cifs/file.c | 32 +++++++++++++++++++++++++++++---
> >   1 file changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> > index 22dfc1f8b4f1..8cdd2f67af24 100644
> > --- a/fs/cifs/file.c
> > +++ b/fs/cifs/file.c
> > @@ -2527,14 +2527,40 @@ wdata_alloc_and_fillpages(pgoff_t tofind, struct address_space *mapping,
> >                            unsigned int *found_pages)
> >   {
> >          struct cifs_writedata *wdata;
> > -
> > +       struct folio_batch fbatch;
> > +       unsigned int i, idx, p, nr;
> >          wdata = cifs_writedata_alloc((unsigned int)tofind,
> >                                       cifs_writev_complete);
> >          if (!wdata)
> >                  return NULL;
> >
> > -       *found_pages = find_get_pages_range_tag(mapping, index, end,
> > -                               PAGECACHE_TAG_DIRTY, tofind, wdata->pages);
> > +       folio_batch_init(&fbatch);
> > +       *found_pages = 0;
> > +


This is really just the top of a while loop:

  while (nr = filemap_get_folios_tag(...)) {

> > +again:
> > +       nr = filemap_get_folios_tag(mapping, index, end,
> > +                               PAGECACHE_TAG_DIRTY, &fbatch);
> > +       if (!nr)
> > +               goto out; /* No dirty pages left in the range */
> > +
> > +       for (i = 0; i < nr; i++) {
> > +               struct folio *folio = fbatch.folios[i];
> > +
> > +               idx = 0;
> > +               p = folio_nr_pages(folio);

And this is a "do {"

> > +add_more:
> > +               wdata->pages[*found_pages] = folio_page(folio, idx);
> > +               folio_get(folio);
> > +               if (++*found_pages == tofind) {
> > +                       folio_batch_release(&fbatch);
> > +                       goto out;
> > +               }
> > +               if (++idx < p)
> > +                       goto add_more;

To here "} while (++idx < p);"

> > +       }
> > +       folio_batch_release(&fbatch);
> > +       goto again;

End while "}"

> > +out:
> >          return wdata;
> >   }
> >
> > --
> > 2.38.1
>
> Could someone review this cifs patch, please? This is one of the
> 2 remaining patches that need to be looked at in the series.

It's otherwise ok.

Tom.
>