linux-kernel - [PATCH v3] drivers: nvme: target: core: Pass lockdep expression to RCU lists

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Message-Id: <20200111073815.7659-1-frextrite@gmail.com>
Date:   Sat, 11 Jan 2020 13:08:16 +0530
From:   Amol Grover <frextrite@...il.com>
To:     Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Amol Grover <frextrite@...il.com>,
        kbuild test robot <lkp@...el.com>
Subject: [PATCH v3] drivers: nvme: target: core: Pass lockdep expression to RCU lists

ctrl->subsys->namespaces and subsys->namespaces are traversed with
list_for_each_entry_rcu outside an RCU read-side critical section
but under the protection of ctrl->subsys->lock and subsys->lock
respectively.

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

Reported-by: kbuild test robot <lkp@...el.com>
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Amol Grover <frextrite@...il.com>
---
v3:
- Fix error reported by kbuild test robot

v2:
- Fix sparse error
  CHECK: Alignment should match open parenthesis
- Remove global macro and use local lockdep expressions

 drivers/nvme/target/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 28438b833c1b..35810a0a8d21 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -555,7 +555,8 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
 	} else {
 		struct nvmet_ns *old;
 
-		list_for_each_entry_rcu(old, &subsys->namespaces, dev_link) {
+		list_for_each_entry_rcu(old, &subsys->namespaces, dev_link,
+					lockdep_is_held(&subsys->lock)) {
 			BUG_ON(ns->nsid == old->nsid);
 			if (ns->nsid < old->nsid)
 				break;
@@ -1172,7 +1173,8 @@ static void nvmet_setup_p2p_ns_map(struct nvmet_ctrl *ctrl,
 
 	ctrl->p2p_client = get_device(req->p2p_client);
 
-	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link)
+	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link,
+				lockdep_is_held(&ctrl->subsys->lock))
 		nvmet_p2pmem_ns_add_p2p(ctrl, ns);
 }
 
-- 
2.24.1