blk-mq: don't schedule block kworker on isolated CPUs

Kernel parameter of `isolcpus=` or 'nohz_full=' are used to isolate CPUs
for specific task, and it isn't expected to let block IO disturb these CPUs.
blk-mq kworker shouldn't be scheduled on isolated CPUs. Also if isolated
CPUs is run for blk-mq kworker, long block IO latency can be caused.

Kernel workqueue only respects CPU isolation for WQ_UNBOUND, for bound
WQ, the responsibility is on user because CPU is specified as WQ API
parameter, such as mod_delayed_work_on(cpu), queue_delayed_work_on(cpu)
and queue_work_on(cpu).

So not run blk-mq kworker on isolated CPUs by removing isolated CPUs
from hctx->cpumask. Meantime use queue map to check if all CPUs in this
hw queue are offline instead of hctx->cpumask, this way can avoid any
cost in fast IO code path, and is safe since hctx->cpumask are only
used in the two cases.

Cc: Tim Chen <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Andrew Theurer <[email protected]>
Cc: Joe Mario <[email protected]>
Cc: Sebastian Jug <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: Tejun Heo <[email protected]>
Tesed-by: Joe Mario <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Reviewed-by: Ewan D. Milne <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

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