[PATCH] locking/rwsem: add scoped guard for down_read_killable()

[Oleg Nesterov <oleg@redhat.com>]

We have lock guards for down_read_trylock/interruptible() but
down_read_killable() is missing.

At least scoped_cond_guard(rwsem_read_kill, signal->exec_update_lock)
can have a lot of users: __pidfd_fget(), mm_access(), find_mm_struct(),
kernel_migrate_pages(), and probably more.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/rwsem.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 6a1a7bae5f81..f0cc72d8f0f2 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -259,6 +259,7 @@ extern void up_write(struct rw_semaphore *sem) __releases(sem);
 DEFINE_LOCK_GUARD_1(rwsem_read, struct rw_semaphore, down_read(_T->lock), up_read(_T->lock))
 DEFINE_LOCK_GUARD_1_COND(rwsem_read, _try, down_read_trylock(_T->lock))
 DEFINE_LOCK_GUARD_1_COND(rwsem_read, _intr, down_read_interruptible(_T->lock), _RET == 0)
+DEFINE_LOCK_GUARD_1_COND(rwsem_read, _kill, down_read_killable(_T->lock), _RET == 0)
 
 DECLARE_LOCK_GUARD_1_ATTRS(rwsem_read, __acquires_shared(_T), __releases_shared(*(struct rw_semaphore **)_T))
 #define class_rwsem_read_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(rwsem_read, _T)
@@ -266,6 +267,8 @@ DECLARE_LOCK_GUARD_1_ATTRS(rwsem_read_try, __acquires_shared(_T), __releases_sha
 #define class_rwsem_read_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(rwsem_read_try, _T)
 DECLARE_LOCK_GUARD_1_ATTRS(rwsem_read_intr, __acquires_shared(_T), __releases_shared(*(struct rw_semaphore **)_T))
 #define class_rwsem_read_intr_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(rwsem_read_intr, _T)
+DECLARE_LOCK_GUARD_1_ATTRS(rwsem_read_kill, __acquires_shared(_T), __releases_shared(*(struct rw_semaphore **)_T))
+#define class_rwsem_read_kill_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(rwsem_read_kill, _T)
 
 DEFINE_LOCK_GUARD_1(rwsem_write, struct rw_semaphore, down_write(_T->lock), up_write(_T->lock))
 DEFINE_LOCK_GUARD_1_COND(rwsem_write, _try, down_write_trylock(_T->lock))
-- 
2.52.0