From 5f00397644e01adfbebafb5d0ebc01eba522709d Mon Sep 17 00:00:00 2001 From: Nate Diller Date: Tue, 24 Jan 2006 10:07:58 +0100 Subject: [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 Signed-off-by: Jens Axboe --- block/elevator.c | 45 ++++++++++++++------------------------------- 1 file changed, 14 insertions(+), 31 deletions(-) (limited to 'block/elevator.c') diff --git a/block/elevator.c b/block/elevator.c index c9f424d5399..dbbea73a8b1 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -139,35 +139,16 @@ 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); + 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); @@ -669,8 +650,10 @@ 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)) - printk(" (default)"); + if (!strcmp(e->elevator_name, chosen_elevator) || + (!*chosen_elevator && + !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) + printk(" (default)"); printk("\n"); return 0; } -- cgit v1.2.3