Commit 248d5ca5 authored Jan 24, 2006 by Nate Diller Committed by Jens Axboe Jan 24, 2006

[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>

parent 5f003976

block/elevator.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -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);

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