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[BLOCK] elevator: allow default scheduler to potentially be modular 

Jens has decided that allowing the default scheduler to be a module is
a bug, and should not be allowed under kconfig.  However, I find that
scenario useful for debugging, and wish for the kernel to be able to
handle this situation without OOPSing, if I enable such an option in
the .config directly.  This patch dynamically checks for the presence
of the compiled-in default, and falls back to no-op, emitting a
suitable error message, when the default is not available

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>
This commit is contained in:
Nate Diller 2006-01-24 10:09:14 +01:00 committed by Jens Axboe
parent 5f00397644
commit 248d5ca5ed
1 changed files with 6 additions and 4 deletions
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8
block/elevator.c
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@ -168,10 +168,12 @@ int elevator_init(request_queue_t *q, char *name)
if (name && !(e = elevator_get(name)))
return -EINVAL;
if (!e && !(e = elevator_get(chosen_elevator))) {
e = elevator_get(CONFIG_DEFAULT_IOSCHED);
if (*chosen_elevator)
if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
printk("I/O scheduler %s not found\n", chosen_elevator);
if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
printk("Default I/O scheduler not found, using no-op\n");
e = elevator_get("noop");
}
eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);