linux-kernel - [PATCH 07/13] readahead: rework loop in page_cache_ra

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Date: Mon, 26 Feb 2024 10:49:30 +0100
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	david@...morbit.com,
	chandan.babu@...cle.com,
	akpm@...ux-foundation.org,
	mcgrof@...nel.org,
	ziy@...dia.com,
	hare@...e.de,
	djwong@...nel.org,
	gost.dev@...sung.com,
	linux-mm@...ck.org,
	willy@...radead.org,
	Pankaj Raghav <p.raghav@...sung.com>
Subject: [PATCH 07/13] readahead: rework loop in page_cache_ra_unbounded()

From: Hannes Reinecke <hare@...e.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@...e.de>
Co-developed-by: Pankaj Raghav <p.raghav@...sung.com>
Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
Acked-by: Darrick J. Wong <djwong@...nel.org>
---
 mm/readahead.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index 325a25e4ee3a..ef0004147952 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -212,7 +212,7 @@ 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
@@ -230,7 +230,7 @@ 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)) {
@@ -243,8 +243,8 @@ 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;
 		}
 
@@ -256,13 +256,14 @@ 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