[PATCH] block/elevator: reduce the critical section

[Hui Su]

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_...@163.com>
---
 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