vdev_elevator_switch() possibly incorrect "none" test

[setharnold]

static int
vdev_elevator_switch(vdev_t *v, char *elevator)
{
        /* ... */
        /* Leave existing scheduler when set to "none" */
        if (strncmp(elevator, "none", 4) && (strlen(elevator) == 4) == 0)
                return (0);

This code is convoluted, with five different equality tests on one line. Testing it in a standalone program it appears to return 0 whenever the 'elevator' input string isn't four characters long. (It looks like the strlen() check was added later in the wrong position.)

I propose this replacement:

if (strcmp(elevator, "none") == 0)
        return (0);

Since vdev_elevator_switch() is only ever called with elevator="noop" perhaps this test could be removed anyway.

Thanks

[behlendorf]

Resolved by 4903926