[PATCH 4.19 081/115] nfsd4: fix up replay_matches_cache()

Greg Kroah-Hartman
2020-01-07T21:08:49Z

From: Scott Mayhew <smayhew@redhat.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@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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))