[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: Nate Diller <nate.diller@gmail.com> Signed-off-by: Jens Axboe <axboe@suse.de>
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1 changed files with 14 additions and 31 deletions
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@ -139,35 +139,16 @@ static int elevator_attach(request_queue_t *q, struct elevator_type *e,
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static char chosen_elevator[16];
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static void elevator_setup_default(void)
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static int __init elevator_setup(char *str)
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{
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struct elevator_type *e;
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/*
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* If default has not been set, use the compiled-in selection.
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*/
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if (!chosen_elevator[0])
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strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);
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/*
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* Be backwards-compatible with previous kernels, so users
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* won't get the wrong elevator.
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*/
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if (!strcmp(chosen_elevator, "as"))
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if (!strcmp(str, "as"))
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strcpy(chosen_elevator, "anticipatory");
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/*
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* If the given scheduler is not available, fall back to the default
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*/
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if ((e = elevator_find(chosen_elevator)))
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elevator_put(e);
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else
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strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);
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}
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static int __init elevator_setup(char *str)
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{
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strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
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strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
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return 0;
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}
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@ -184,15 +165,15 @@ int elevator_init(request_queue_t *q, char *name)
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q->end_sector = 0;
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q->boundary_rq = NULL;
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elevator_setup_default();
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if (!name)
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name = chosen_elevator;
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e = elevator_get(name);
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if (!e)
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if (name && !(e = elevator_get(name)))
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return -EINVAL;
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if (!e && !(e = elevator_get(chosen_elevator))) {
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e = elevator_get(CONFIG_DEFAULT_IOSCHED);
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if (*chosen_elevator)
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printk("I/O scheduler %s not found\n", chosen_elevator);
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}
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eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
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if (!eq) {
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elevator_put(e);
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@ -669,8 +650,10 @@ int elv_register(struct elevator_type *e)
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spin_unlock_irq(&elv_list_lock);
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printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
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if (!strcmp(e->elevator_name, chosen_elevator))
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printk(" (default)");
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if (!strcmp(e->elevator_name, chosen_elevator) ||
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(!*chosen_elevator &&
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!strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
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printk(" (default)");
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printk("\n");
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return 0;
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}
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