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

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Message-Id: <20200110132356.27110-1-frextrite@gmail.com>
Date:   Fri, 10 Jan 2020 18:53:58 +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>
Subject: [PATCH] drivers: nvme: target: core: Pass lockdep expression to RCU lists

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

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

Add macro for the corresponding lockdep expression to make the code
clean and concise.

Signed-off-by: Amol Grover <frextrite@...il.com>
---
 drivers/nvme/target/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 28438b833c1b..7caab4ba6a04 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -15,6 +15,9 @@
 
 #include "nvmet.h"
 
+#define subsys_lock_held() \
+	lockdep_is_held(&subsys->lock)
+
 struct workqueue_struct *buffered_io_wq;
 static const struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
 static DEFINE_IDA(cntlid_ida);
@@ -555,7 +558,8 @@ 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,
+							subsys_lock_held()) {
 			BUG_ON(ns->nsid == old->nsid);
 			if (ns->nsid < old->nsid)
 				break;
@@ -1172,7 +1176,8 @@ 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,
+							subsys_lock_held())
 		nvmet_p2pmem_ns_add_p2p(ctrl, ns);
 }
 
-- 
2.24.1