Commit 5f003976 authored by Nate Diller's avatar Nate Diller Committed by Jens Axboe
Browse files

[BLOCK] elevator: default choice selection 



My previous default iosched patch did a poor job dealing with the
'elevator=' boot-time option.  The old behavior falls back to the
compiled-in default if the requested one is not registered at boot
time.  This patch dynamically evaluates which default
to use, and emits a suitable error message when the requested scheduler
is not available.  It also does the 'as' -> 'anticipatory' conversion
before elevator registration, which along with a modified registration
function, allows it to correctly indicate which default scheduler is
in use.

Tested for a range of boot options on 2.6.16-rc1-mm2.

Signed-off-by: default avatarNate Diller <nate.diller@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 53e86061

block/elevator.c

+14 −31
Original line number Diff line number Diff line
@@ -139,34 +139,15 @@ static int elevator_attach(request_queue_t *q, struct elevator_type *e, 


static char chosen_elevator[16];



static void elevator_setup_default(void)

static int __init elevator_setup(char *str)

{

	struct elevator_type *e;



	/*

	 * If default has not been set, use the compiled-in selection.

	 */

	if (!chosen_elevator[0])

		strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);



	/*

	 * Be backwards-compatible with previous kernels, so users

	 * won't get the wrong elevator.

	 */

	if (!strcmp(chosen_elevator, "as"))

	if (!strcmp(str, "as"))

		strcpy(chosen_elevator, "anticipatory");



 	/*

 	 * If the given scheduler is not available, fall back to the default

 	 */

 	if ((e = elevator_find(chosen_elevator)))

		elevator_put(e);

	else

 		strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);

}



static int __init elevator_setup(char *str)

{

		strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);

	return 0;

}
@@ -184,15 +165,15 @@ int elevator_init(request_queue_t *q, char *name) 
	q->end_sector = 0;

	q->boundary_rq = NULL;



	elevator_setup_default();



	if (!name)

		name = chosen_elevator;



	e = elevator_get(name);

	if (!e)

	if (name && !(e = elevator_get(name)))

		return -EINVAL;



	if (!e && !(e = elevator_get(chosen_elevator))) {

		e = elevator_get(CONFIG_DEFAULT_IOSCHED);

		if (*chosen_elevator)

			printk("I/O scheduler %s not found\n", chosen_elevator);

	}



	eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);

	if (!eq) {

		elevator_put(e);
@@ -669,7 +650,9 @@ int elv_register(struct elevator_type *e) 
	spin_unlock_irq(&elv_list_lock);



	printk(KERN_INFO "io scheduler %s registered", e->elevator_name);

	if (!strcmp(e->elevator_name, chosen_elevator))

	if (!strcmp(e->elevator_name, chosen_elevator) ||

			(!*chosen_elevator &&

			 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))

				printk(" (default)");

	printk("\n");

	return 0;

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