locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()

mainline inclusion
from mainline-v5.11-rc1
commit c8fe8b05
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7A0N9
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c8fe8b0564388f41147326f31e4587171aacccd4

--------------------------------

The atomic count value right after reader count increment can be useful
to determine the rwsem state at trylock time. So the count value is
passed down to rwsem_down_read_slowpath() to be used when appropriate.
Signed-off-by: NWaiman Long <longman@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NDavidlohr Bueso <dbueso@suse.de>
Link: https://lkml.kernel.org/r/20201121041416.12285-2-longman@redhat.com
Conflicts:
  kernel/locking/rwsem.c
[yyl: No functional changed.]
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
(cherry picked from commit 6f54c87c)

kernel/locking/rwsem.c

@@ -270,14 +270,14 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
 					  owner | RWSEM_NONSPINNABLE));
 }
 
-static inline bool rwsem_read_trylock(struct rw_semaphore *sem)
+static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
 {
-	long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
+	*cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
 
-	if (WARN_ON_ONCE(cnt < 0))
+	if (WARN_ON_ONCE(*cntp < 0))
 		rwsem_set_nonspinnable(sem);
 
-	if (!(cnt & RWSEM_READ_FAILED_MASK)) {
+	if (!(*cntp & RWSEM_READ_FAILED_MASK)) {
 		rwsem_set_reader_owned(sem);
 		return true;
 	}
@@ -996,9 +996,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable)
  * Wait for the read lock to be granted
  */
 static struct rw_semaphore __sched *
-rwsem_down_read_slowpath(struct rw_semaphore *sem, int state)
+rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state)
 {
-	long count, adjustment = -RWSEM_READER_BIAS;
+	long adjustment = -RWSEM_READER_BIAS;
 	struct rwsem_waiter waiter;
 	DEFINE_WAKE_Q(wake_q);
 	bool wake = false;
@@ -1344,16 +1344,20 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
  */
 static inline void __down_read(struct rw_semaphore *sem)
 {
-	if (!rwsem_read_trylock(sem)) {
-		rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE);
+	long count;
+
+	if (!rwsem_read_trylock(sem, &count)) {
+		rwsem_down_read_slowpath(sem, count, TASK_UNINTERRUPTIBLE);
 		DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
 	}
 }
 
 static inline int __down_read_interruptible(struct rw_semaphore *sem)
 {
-	if (!rwsem_read_trylock(sem)) {
-		if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))
+	long count;
+
+	if (!rwsem_read_trylock(sem, &count)) {
+		if (IS_ERR(rwsem_down_read_slowpath(sem, count, TASK_INTERRUPTIBLE)))
 			return -EINTR;
 		DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
 	}
@@ -1362,8 +1366,10 @@ static inline int __down_read_interruptible(struct rw_semaphore *sem)
 
 static inline int __down_read_killable(struct rw_semaphore *sem)
 {
-	if (!rwsem_read_trylock(sem)) {
-		if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE)))
+	long count;
+
+	if (!rwsem_read_trylock(sem, &count)) {
+		if (IS_ERR(rwsem_down_read_slowpath(sem, count, TASK_KILLABLE)))
 			return -EINTR;
 		DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
 	}