linux-kernel - [PATCH v3 02/12] mm/shmem: Use pagevec_lookup in shmem_unlock

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Message-Id: <20201026041408.25230-3-willy@infradead.org>
Date:   Mon, 26 Oct 2020 04:13:58 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Dave Chinner <dchinner@...hat.com>,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
        William Kucharski <william.kucharski@...cle.com>
Subject: [PATCH v3 02/12] mm/shmem: Use pagevec_lookup in shmem_unlock_mapping

The comment shows that the reason for using find_get_entries() is now
stale; find_get_pages() will not return 0 if it hits a consecutive run
of swap entries, and I don't believe it has since 2011.  pagevec_lookup()
is a simpler function to use than find_get_pages(), so use it instead.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
---
 mm/shmem.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 537c137698f8..a33972126b60 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -842,7 +842,6 @@ unsigned long shmem_swap_usage(struct vm_area_struct *vma)
 void shmem_unlock_mapping(struct address_space *mapping)
 {
 	struct pagevec pvec;
-	pgoff_t indices[PAGEVEC_SIZE];
 	pgoff_t index = 0;
 
 	pagevec_init(&pvec);
@@ -850,16 +849,8 @@ void shmem_unlock_mapping(struct address_space *mapping)
 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 	 */
 	while (!mapping_unevictable(mapping)) {
-		/*
-		 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
-		 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
-		 */
-		pvec.nr = find_get_entries(mapping, index,
-					   PAGEVEC_SIZE, pvec.pages, indices);
-		if (!pvec.nr)
+		if (!pagevec_lookup(&pvec, mapping, &index))
 			break;
-		index = indices[pvec.nr - 1] + 1;
-		pagevec_remove_exceptionals(&pvec);
 		check_move_unevictable_pages(&pvec);
 		pagevec_release(&pvec);
 		cond_resched();
-- 
2.28.0