Re: [RFC v2 06/14] readahead: rework loop in page_cache_ra_unbounded()

Darrick J. Wong
2024-02-13T16:47:03Z

On Tue, Feb 13, 2024 at 10:37:05AM +0100, Pankaj Raghav (Samsung) wrote:
> From: Hannes Reinecke <hare@suse.de>
>
> Rework the loop in page_cache_ra_unbounded() to advance with
> the number of pages in a folio instead of just one page at a time.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>

Acked-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> mm/readahead.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 5e1ec7705c78..13b62cbd3b79 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -213,7 +213,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> struct address_space *mapping = ractl->mapping;
> unsigned long index = readahead_index(ractl);
> gfp_t gfp_mask = readahead_gfp_mask(mapping);
> - unsigned long i;
> + unsigned long i = 0;
>
> /*
> * Partway through the readahead operation, we will have added
> @@ -231,7 +231,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
> /*
> * Preallocate as many pages as we will need.
> */
> - for (i = 0; i < nr_to_read; i++) {
> + while (i < nr_to_read) {
> struct folio *folio = xa_load(&mapping->i_pages, index + i);
>
> if (folio && !xa_is_value(folio)) {
> @@ -244,8 +244,8 @@ 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;
> }
>
> @@ -257,13 +257,14 @@ 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;
> }
> if (i == nr_to_read - lookahead_size)
> folio_set_readahead(folio);
> ractl->_workingset |= folio_test_workingset(folio);
> - ractl->_nr_pages++;
> + ractl->_nr_pages += folio_nr_pages(folio);
> + i += folio_nr_pages(folio);
> }
>
> /*
> --
> 2.43.0
>
>