dm mpath: do not lock up a CPU with requeuing activity

dm mpath: do not lock up a CPU with requeuing activity

When using the block layer in single queue mode, get_request()
returns ERR_PTR(-EAGAIN) if the queue is dying and the REQ_NOWAIT
flag has been passed to get_request(). Avoid that the kernel
reports soft lockup complaints in this case due to continuous
requeuing activity.

Fixes: 7083abbbf ("dm mpath: avoid that path removal can trigger an infinite loop")
Cc: [email protected]
Signed-off-by: Bart Van Assche <[email protected]>
Tested-by: Laurence Oberman <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>