[PATCH 2/3] drivers: target: target_core_tpg: Pass lockdep expression to RCU lists

Amol Grover
2020-01-10T12:45:16Z

tpg->tpg_lun_hlist is traversed with hlist_for_each_entry_rcu
outside an RCU read-side critical section but under the
protection of tpg->tpg_lun_mutex.

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@gmail.com>
---
drivers/target/target_core_tpg.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index d24e0a3ba3ff..bc1c5dda81bf 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -30,6 +30,9 @@
#include "target_core_pr.h"
#include "target_core_ua.h"

+#define tpg_lun_mutex_held() \
+ lockdep_is_held(&tpg->tpg_lun_mutex)
+
extern struct se_device *g_lun0_dev;

/* __core_tpg_get_initiator_node_acl():
@@ -110,12 +113,12 @@ void core_tpg_add_node_to_devs(
struct se_device *dev;

mutex_lock(&tpg->tpg_lun_mutex);
- hlist_for_each_entry_rcu(lun, &tpg->tpg_lun_hlist, link) {
+ hlist_for_each_entry_rcu(lun, &tpg->tpg_lun_hlist, link,
+ tpg_lun_mutex_held()) {
if (lun_orig && lun != lun_orig)
continue;

- dev = rcu_dereference_check(lun->lun_se_dev,
- lockdep_is_held(&tpg->tpg_lun_mutex));
+ dev = rcu_dereference_check(lun->lun_se_dev, tpg_lun_mutex_held());
/*
* By default in LIO-Target $FABRIC_MOD,
* demo_mode_write_protect is ON, or READ_ONLY;
--
2.24.1