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

Pankaj Raghav (Samsung)
2024-02-13T09:37:43Z

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>
---
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