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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Howells <dhowells@redhat.com>,
        Jeff Layton <jlayton@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Steve French <stfrench@microsoft.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.18 0935/1095] cifs: Fix memory leak when using fscache
Date:   Mon, 15 Aug 2022 20:05:34 +0200
Message-Id: <20220815180507.891590000@linuxfoundation.org>
In-Reply-To: <20220815180429.240518113@linuxfoundation.org>
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From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit c6f62f81b488d00afaa86bae26c6ce9ab12c709e ]

If we hit the 'index == next_cached' case, we leak a refcount on the
struct page.  Fix this by using readahead_folio() which takes care of
the refcount for you.

Fixes: 0174ee9947bd ("cifs: Implement cache I/O by accessing the cache directly")
Cc: David Howells <dhowells@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/file.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 58dce567ceaf..3d475f1847a4 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4456,10 +4456,10 @@ static void cifs_readahead(struct readahead_control *ractl)
 				 * TODO: Send a whole batch of pages to be read
 				 * by the cache.
 				 */
-				page = readahead_page(ractl);
-				last_batch_size = 1 << thp_order(page);
+				struct folio *folio = readahead_folio(ractl);
+				last_batch_size = folio_nr_pages(folio);
 				if (cifs_readpage_from_fscache(ractl->mapping->host,
-							       page) < 0) {
+							       &folio->page) < 0) {
 					/*
 					 * TODO: Deal with cache read failure
 					 * here, but for the moment, delegate
@@ -4467,7 +4467,7 @@ static void cifs_readahead(struct readahead_control *ractl)
 					 */
 					caching = false;
 				}
-				unlock_page(page);
+				folio_unlock(folio);
 				next_cached++;
 				cache_nr_pages--;
 				if (cache_nr_pages == 0)
-- 
2.35.1