From: Jens Axboe <axboe@kernel.dk>
To: Hui Su <sh_def@163.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block/elevator: reduce the critical section
Date: Mon, 19 Oct 2020 11:23:48 -0600 [thread overview]
Message-ID: <ea4495c3-0003-786d-82e4-3693f349890a@kernel.dk> (raw)
In-Reply-To: <20201019164246.GA79115@rlk>
On 10/19/20 10:42 AM, Hui Su wrote:
> @@ -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
prev parent reply other threads:[~2020-10-19 17:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 16:42 [PATCH] block/elevator: reduce the critical section Hui Su
2020-10-19 16:50 ` Jens Axboe
2020-10-19 17:23 ` Jens Axboe [this message]
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