[PATCH] block/elevator: reduce the critical section

From: Hui Su
Date: Mon Oct 19 2020 - 12:43:24 EST


1.reduce the critical section in elevator_get().
2.reduce the critical section in elevator_get_by_features().
3.remove the found variable.

the elv_list_lock is used to protect the elv_list,
and the operations of elevator_type does not need
to be protected.

Signed-off-by: Hui Su <sh_def@xxxxxxx>
---
block/elevator.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 293c5c81397a..727902b31954 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -151,11 +151,11 @@ static struct elevator_type *elevator_get(struct request_queue *q,
spin_lock(&elv_list_lock);
e = elevator_find(name, q->required_elevator_features);
}
+ spin_unlock(&elv_list_lock);

if (e && !try_module_get(e->elevator_owner))
e = NULL;

- spin_unlock(&elv_list_lock);
return e;
}

@@ -633,23 +633,21 @@ static struct elevator_type *elevator_get_default(struct request_queue *q)
*/
static struct elevator_type *elevator_get_by_features(struct request_queue *q)
{
- struct elevator_type *e, *found = NULL;
+ struct elevator_type *e = NULL;

spin_lock(&elv_list_lock);
-
list_for_each_entry(e, &elv_list, list) {
if (elv_support_features(e->elevator_features,
q->required_elevator_features)) {
- found = e;
break;
}
}
+ spin_unlock(&elv_list_lock);

- if (found && !try_module_get(found->elevator_owner))
- found = NULL;
+ if (e && !try_module_get(e->elevator_owner))
+ e = NULL;

- spin_unlock(&elv_list_lock);
- return found;
+ return e;
}

/*
--
2.25.1