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From:   Benjamin Coddington <bcodding@redhat.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH 2/3] NFSv4: Refactor nfs_need_update_open_stateid()
Date:   Mon, 21 Sep 2020 07:04:40 -0400
Message-Id: <d6c4cd73c3546057edfe8d80512b274bb431d68e.1600686204.git.bcodding@redhat.com>
In-Reply-To: <5a7f6bbf4cf2038634a572f42ad80e95a8d0ae9c.1600686204.git.bcodding@redhat.com>
References: <5a7f6bbf4cf2038634a572f42ad80e95a8d0ae9c.1600686204.git.bcodding@redhat.com>
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The logic was becoming difficult to follow.  Add some comments and local
variables to clarify the behavior.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 fs/nfs/nfs4proc.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 9ced7a62c05e..499f978d48aa 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1568,23 +1568,34 @@ static void nfs_test_and_clear_all_open_stateid(struct nfs4_state *state)
 static bool nfs_need_update_open_stateid(struct nfs4_state *state,
 		const nfs4_stateid *stateid)
 {
-	if (test_bit(NFS_OPEN_STATE, &state->flags) == 0 ||
-	    !nfs4_stateid_match_other(stateid, &state->open_stateid)) {
-		if (stateid->seqid == cpu_to_be32(1)) {
+	bool state_matches_other = nfs4_stateid_match_other(stateid, &state->open_stateid);
+	bool seqid_one = stateid->seqid == cpu_to_be32(1);
+
+	if (test_bit(NFS_OPEN_STATE, &state->flags)) {
+		/* The common case - we're updating to a new sequence number */
+		if (state_matches_other && nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
+			nfs_state_log_out_of_order_open_stateid(state, stateid);
+			return true;
+		}
+		/* We lost a race with a self-bumping close, do recovery */
+		if (!state_matches_other) {
+			trace_printk("lost race to self-bump close\n");
+			return false;
+		}
+	} else {
+		/* The common case, this is the first OPEN */
+		if (!state_matches_other && seqid_one) {
 			nfs_state_log_update_open_stateid(state);
-		} else {
-			if (!nfs4_stateid_match_other(stateid, &state->open_stateid))
-				return false;
-			else
-				set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
+			return true;
+		}
+		/* We lost a race either with a self-bumping close, OR with the first OPEN */
+		if (!state_matches_other && !seqid_one) {
+			trace_printk("lost race to self-bump close OR first OPEN\n");
+			set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
+			return true;
 		}
-		return true;
-	}
-
-	if (nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
-		nfs_state_log_out_of_order_open_stateid(state, stateid);
-		return true;
 	}
+	/* Should be impossible to reach: */
 	return false;
 }
 
-- 
2.20.1