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From:   trondmy@kernel.org
To:     Nagendra S Tomar <natomar@microsoft.com>
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH] NFS: Only change the cookie verifier if the directory page cache is empty
Date:   Wed, 17 Mar 2021 09:01:10 -0400
Message-Id: <20210317130110.1257066-1-trondmy@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

The cached NFSv3/v4 readdir cookies are associated with a verifier,
which is checked by the server on subsequent calls to readdir, and is
only expected to change when the cookies (and hence also the page cache
contents) are considered invalid.
We therefore do have to store the verifier, but only when the page cache
is empty.

Fixes: b593c09f83a2 ("NFS: Improve handling of directory verifiers")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/dir.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 2cf2a7d92faf..0cd7c59a6601 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -929,7 +929,12 @@ static int find_and_lock_cache_page(struct nfs_readdir_descriptor *desc)
 			}
 			return res;
 		}
-		memcpy(nfsi->cookieverf, verf, sizeof(nfsi->cookieverf));
+		/*
+		 * Set the cookie verifier if the page cache was empty
+		 */
+		if (desc->page_index == 0)
+			memcpy(nfsi->cookieverf, verf,
+			       sizeof(nfsi->cookieverf));
 	}
 	res = nfs_readdir_search_array(desc);
 	if (res == 0) {
-- 
2.30.2