linux-kernel - [PATCH] sunrpc: Pass lockdep expression to RCU lists

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Date:   Wed, 19 Feb 2020 15:05:05 +0530
From:   Amol Grover <frextrite@...il.com>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        Amol Grover <frextrite@...il.com>
Subject: [PATCH] sunrpc: Pass lockdep expression to RCU lists

detail->hash_table[] is traversed using hlist_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of detail->hash_lock.

Hence, add corresponding lockdep expression to silence false-positive
warnings, and harden RCU lists.

Signed-off-by: Amol Grover <frextrite@...il.com>
---
 net/sunrpc/cache.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index f740cb51802a..5db5f5b94726 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -97,7 +97,8 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
 	spin_lock(&detail->hash_lock);
 
 	/* check if entry appeared while we slept */
-	hlist_for_each_entry_rcu(tmp, head, cache_list) {
+	hlist_for_each_entry_rcu(tmp, head, cache_list,
+				 lockdep_is_held(&detail->hash_lock)) {
 		if (detail->match(tmp, key)) {
 			if (cache_is_expired(detail, tmp)) {
 				hlist_del_init_rcu(&tmp->cache_list);
-- 
2.24.1