linux-kernel - [PATCH 4.19 081/115] nfsd4: fix up replay_matches

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Message-Id: <20200107205304.751841084@linuxfoundation.org>
Date:   Tue,  7 Jan 2020 21:54:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Scott Mayhew <smayhew@...hat.com>,
        "J. Bruce Fields" <bfields@...hat.com>
Subject: [PATCH 4.19 081/115] nfsd4: fix up replay_matches_cache()

From: Scott Mayhew <smayhew@...hat.com>

commit 6e73e92b155c868ff7fce9d108839668caf1d9be upstream.

When running an nfs stress test, I see quite a few cached replies that
don't match up with the actual request.  The first comment in
replay_matches_cache() makes sense, but the code doesn't seem to
match... fix it.

This isn't exactly a bugfix, as the server isn't required to catch every
case of a false retry.  So, we may as well do this, but if this is
fixing a problem then that suggests there's a client bug.

Fixes: 53da6a53e1d4 ("nfsd4: catch some false session retries")
Signed-off-by: Scott Mayhew <smayhew@...hat.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfsd/nfs4state.c |   15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3072,12 +3072,17 @@ static bool replay_matches_cache(struct
 	    (bool)seq->cachethis)
 		return false;
 	/*
-	 * If there's an error than the reply can have fewer ops than
-	 * the call.  But if we cached a reply with *more* ops than the
-	 * call you're sending us now, then this new call is clearly not
-	 * really a replay of the old one:
+	 * If there's an error then the reply can have fewer ops than
+	 * the call.
 	 */
-	if (slot->sl_opcnt < argp->opcnt)
+	if (slot->sl_opcnt < argp->opcnt && !slot->sl_status)
+		return false;
+	/*
+	 * But if we cached a reply with *more* ops than the call you're
+	 * sending us now, then this new call is clearly not really a
+	 * replay of the old one:
+	 */
+	if (slot->sl_opcnt > argp->opcnt)
 		return false;
 	/* This is the only check explicitly called by spec: */
 	if (!same_creds(&rqstp->rq_cred, &slot->sl_cred))