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From:   trondmy@kernel.org
To:     linux-nfs@vger.kernel.org
Subject: [PATCH 5/5] NFS: Fix dentry verifier races
Date:   Wed, 29 Sep 2021 09:49:44 -0400
Message-Id: <20210929134944.632844-5-trondmy@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

If the directory changed while we were revalidating the dentry, then
don't update the dentry verifier. There is no value in setting the
verifier to an older value, and we could end up overwriting a more up to
date verifier from a parallel revalidation.

Fixes: efeda80da38d ("NFSv4: Fix revalidation of dentries with delegations")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/dir.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 358033aea235..033e9b145627 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1276,13 +1276,12 @@ static bool nfs_verifier_is_delegated(struct dentry *dentry)
 static void nfs_set_verifier_locked(struct dentry *dentry, unsigned long verf)
 {
 	struct inode *inode = d_inode(dentry);
+	struct inode *dir = d_inode(dentry->d_parent);
 
-	if (!nfs_verifier_is_delegated(dentry) &&
-	    !nfs_verify_change_attribute(d_inode(dentry->d_parent), verf))
-		goto out;
+	if (!nfs_verify_change_attribute(dir, verf))
+		return;
 	if (inode && NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
 		nfs_set_verifier_delegated(&verf);
-out:
 	dentry->d_time = verf;
 }
 
-- 
2.31.1