[PATCH v2 1/3] drivers: target: target_core_device: Pass lockdep expression to RCU lists

Amol Grover
2020-01-10T17:06:50Z

nacl->lun_entry_hlist is traversed with hlist_for_each_entry_rcu
outside an RCU read-side critical section but under the
protection of nacl->lun_entry_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>
---
v2:
- Fix sparse error
CHECK: Alignment should match open parenthesis

drivers/target/target_core_device.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 2d19f0e332b0..7627583e2509 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -36,6 +36,9 @@
#include "target_core_pr.h"
#include "target_core_ua.h"

+#define lun_entry_mutex_held() \
+ lockdep_is_held(&nacl->lun_entry_mutex)
+
static DEFINE_MUTEX(device_mutex);
static LIST_HEAD(device_list);
static DEFINE_IDR(devices_idr);
@@ -247,9 +250,10 @@ void core_free_device_list_for_node(
struct se_dev_entry *deve;

mutex_lock(&nacl->lun_entry_mutex);
- hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
+ hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link,
+ lun_entry_mutex_held()) {
struct se_lun *lun = rcu_dereference_check(deve->se_lun,
- lockdep_is_held(&nacl->lun_entry_mutex));
+ lun_entry_mutex_held());
core_disable_device_list_for_node(lun, deve, nacl, tpg);
}
mutex_unlock(&nacl->lun_entry_mutex);
@@ -276,7 +280,8 @@ struct se_dev_entry *target_nacl_find_deve(struct se_node_acl *nacl, u64 mapped_
{
struct se_dev_entry *deve;

- hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link)
+ hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link,
+ rcu_read_lock_held() || lun_entry_mutex_held())
if (deve->mapped_lun == mapped_lun)
return deve;

@@ -339,7 +344,7 @@ int core_enable_device_list_for_node(
orig = target_nacl_find_deve(nacl, mapped_lun);
if (orig && orig->se_lun) {
struct se_lun *orig_lun = rcu_dereference_check(orig->se_lun,
- lockdep_is_held(&nacl->lun_entry_mutex));
+ lun_entry_mutex_held());

if (orig_lun != lun) {
pr_err("Existing orig->se_lun doesn't match new lun"
@@ -460,9 +465,10 @@ void core_clear_lun_from_tpg(struct se_lun *lun, struct se_portal_group *tpg)
list_for_each_entry(nacl, &tpg->acl_node_list, acl_list) {

mutex_lock(&nacl->lun_entry_mutex);
- hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
+ hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link,
+ lun_entry_mutex_held()) {
struct se_lun *tmp_lun = rcu_dereference_check(deve->se_lun,
- lockdep_is_held(&nacl->lun_entry_mutex));
+ lun_entry_mutex_held());

if (lun != tmp_lun)
continue;
--
2.24.1