linux-kernel - [PATCH 5/5] swap: avoid ra statistic lost when swapin races

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Message-Id: <20221208180209.50845-6-ryncsn@gmail.com>
Date:   Fri,  9 Dec 2022 02:02:09 +0800
From:   Kairui Song <ryncsn@...il.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Hugh Dickins <hughd@...gle.com>,
        Kairui Song <kasong@...cent.com>
Subject: [PATCH 5/5] swap: avoid ra statistic lost when swapin races

From: Kairui Song <kasong@...cent.com>

__read_swap_cache_async should just call swap_cache_get_folio for trying
to look up the swap cache. Because swap_cache_get_folio handles the
readahead statistic, and clears the RA flag, looking up the cache
directly will skip these parts.

And the comment no longer applies after commit 442701e7058b
("mm/swap: remove swap_cache_info statistics"), just remove them.

Fixes: 442701e7058b ("mm/swap: remove swap_cache_info statistics")
Signed-off-by: Kairui Song <kasong@...cent.com>
---
 mm/swap_state.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index eba388f67741..f39cfb62551d 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -418,15 +418,12 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	for (;;) {
 		int err;
 		/*
-		 * First check the swap cache.  Since this is normally
-		 * called after swap_cache_get_folio() failed, re-calling
-		 * that would confuse statistics.
+		 * First check the swap cache in case of race.
 		 */
 		si = get_swap_device(entry);
 		if (!si)
 			return NULL;
-		folio = filemap_get_folio(swap_address_space(entry),
-						swp_offset(entry));
+		folio = swap_cache_get_folio(entry, vma, addr);
 		put_swap_device(si);
 		if (folio)
 			return folio_file_page(folio, swp_offset(entry));
-- 
2.35.2