linux-kernel - [PATCH v2 2/8] mm/hugetlb: convert hugetlbfs_pagecache

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Date:   Wed, 25 Jan 2023 09:05:31 -0800
From:   Sidhartha Kumar <sidhartha.kumar@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, songmuchun@...edance.com,
        mike.kravetz@...cle.com, willy@...radead.org, jhubbard@...dia.com,
        gerald.schaefer@...ux.ibm.com,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>
Subject: [PATCH v2 2/8] mm/hugetlb: convert hugetlbfs_pagecache_present() to folios

Refactor hugetlbfs_pagecache_present() to avoid getting and dropping
a refcount on a page. Use RCU and page_cache_next_miss() instead.

Suggested-by: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
---
 mm/hugetlb.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 849206e94742..e506a46b7871 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5651,17 +5651,15 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
 static bool hugetlbfs_pagecache_present(struct hstate *h,
 			struct vm_area_struct *vma, unsigned long address)
 {
-	struct address_space *mapping;
-	pgoff_t idx;
-	struct page *page;
+	struct address_space *mapping = vma->vm_file->f_mapping;
+	pgoff_t idx = vma_hugecache_offset(h, vma, address);
+	bool present;
 
-	mapping = vma->vm_file->f_mapping;
-	idx = vma_hugecache_offset(h, vma, address);
+	rcu_read_lock();
+	present = page_cache_next_miss(mapping, idx, 1) != idx;
+	rcu_read_unlock();
 
-	page = find_get_page(mapping, idx);
-	if (page)
-		put_page(page);
-	return page != NULL;
+	return present;
 }
 
 int hugetlb_add_to_page_cache(struct page *page, struct address_space *mapping,
-- 
2.39.1