Re: [PATCH] block/elevator: reduce the critical section
From: Jens Axboe <axboe@kernel.dk>
Date: 2020-10-19 17:23:53
Also in:
lkml
On 10/19/20 10:42 AM, Hui Su wrote:
quoted hunk ↗ jump to hunk
@@ -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; }
This looks wrong as well. If we don't match the elevator, then we just return the last one. Or maybe even a totally invalid entry, depending on how the list iteration works. -- Jens Axboe