On Mon, 18 Feb 2008 19:16:30 +0100 Jens Axboe <[EMAIL PROTECTED]> wrote:
> On Tue, Feb 12 2008, Andrew Morton wrote:
> > On Sat, 09 Feb 2008 08:30:40 -0500
> > Paul Clements <[EMAIL PROTECTED]> wrote:
> >
> > > + old_e = disk->queue->elevator;
> > > + if (elevator_init(disk->queue, "deadline") == 0 ||
> > > + elevator_init(disk->queue, "noop") == 0) {
> > > + elevator_exit(old_e);
> > > + }
> > > }
> >
> > afacit elevator_init() will not trigger a request_module(). And you really
> > do want to trigger the request_module() here. Perhaps the block layer
> > should provide a means of doing so?
>
> Good point, I think elevator_get() should do that automatically. Does
> this look sane?
>
> diff --git a/block/elevator.c b/block/elevator.c
> index bafbae0..88318c3 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -134,6 +134,21 @@ static struct elevator_type *elevator_get(const char
> *name)
> spin_lock(&elv_list_lock);
>
> e = elevator_find(name);
> + if (!e) {
> + char elv[ELV_NAME_MAX + strlen("-iosched")];
> +
> + spin_unlock(&elv_list_lock);
> +
> + if (!strcmp(name, "anticipatory"))
> + sprintf(elv, "as-iosched");
> + else
> + sprintf(elv, "%s-iosched", name);
> +
> + request_module(elv);
> + spin_lock(&elv_list_lock);
> + e = elevator_find(name);
> + }
> +
> if (e && !try_module_get(e->elevator_owner))
> e = NULL;
Looks nice and simple. There might be some of the usual ordering problems
when this is called during boot, maybe is-initramfs-available-yet problems,
etc. But it's unlikely to make things regress from where they are now.
Should we emit a warning if the desired elevator wasn't available?
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