linux-kernel - [PATCH 2/2] fs: hugetlbfs: Fix logic to skip allocation on hit in page cache

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Message-ID: <f15f57def8e69cf288f0646f819b784fe15fabe2.1683069252.git.ackerleytng@google.com>
Date:   Tue,  2 May 2023 23:56:03 +0000
From:   Ackerley Tng <ackerleytng@...gle.com>
To:     akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mike.kravetz@...cle.com, muchun.song@...ux.dev,
        willy@...radead.org, sidhartha.kumar@...cle.com,
        jhubbard@...dia.com
Cc:     vannapurve@...gle.com, erdemaktas@...gle.com,
        Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH 2/2] fs: hugetlbfs: Fix logic to skip allocation on hit in
 page cache

When fallocate() is called twice on the same offset in the file, the
second fallocate() should succeed.

page_cache_next_miss() always advances index before returning, so even
on a page cache hit, the check would set present to false.

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
 fs/hugetlbfs/inode.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index ecfdfb2529a3..f640cff1bbce 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -821,7 +821,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
 		 */
 		struct folio *folio;
 		unsigned long addr;
-		bool present;
 
 		cond_resched();
 
@@ -845,10 +844,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
 		mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
 		/* See if already present in mapping to avoid alloc/free */
-		rcu_read_lock();
-		present = page_cache_next_miss(mapping, index, 1) != index;
-		rcu_read_unlock();
-		if (present) {
+		if (filemap_has_folio(mapping, index)) {
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 			hugetlb_drop_vma_policy(&pseudo_vma);
 			continue;
-- 
2.40.1.495.gc816e09b53d-goog