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block: fix elevator_get_by_features()

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The lookup logic is broken - 'e' will never be NULL, even if the
list is empty. Maintain lookup hit in a separate variable instead.

Fixes: a0958ba7fc ("block: Improve default elevator selection")
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2019-09-06 07:02:31 -06:00
parent ebddd2a153
commit a26142559c
1 changed files with 7 additions and 6 deletions
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13
block/elevator.c
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@ -668,22 +668,23 @@ static struct elevator_type *elevator_get_default(struct request_queue *q)
*/ */
static struct elevator_type *elevator_get_by_features(struct request_queue *q) static struct elevator_type *elevator_get_by_features(struct request_queue *q)
{ {
struct elevator_type *e; struct elevator_type *e, *found = NULL;
spin_lock(&elv_list_lock); spin_lock(&elv_list_lock);
list_for_each_entry(e, &elv_list, list) { list_for_each_entry(e, &elv_list, list) {
if (elv_support_features(e->elevator_features, if (elv_support_features(e->elevator_features,
q->required_elevator_features)) q->required_elevator_features)) {
found = e;
break; break;
}
} }
if (e && !try_module_get(e->elevator_owner)) if (found && !try_module_get(found->elevator_owner))
e = NULL; found = NULL;
spin_unlock(&elv_list_lock); spin_unlock(&elv_list_lock);
return found;
return e;
} }
/* /*