Christoph Hellwig complained about the following soft lockup warning
when running scrub after generic/175 when preemption is disabled and
slub debugging is enabled:
If preemption is disabled, all metadata buffers needed to perform the
scrub are already in memory, and there are a lot of records to check,
it's possible that the scrub thread will run for an extended period of
time without sleeping for IO or any other reason. Then the watchdog
timer or the RCU stall timeout can trigger, producing the backtrace
above.
To fix this problem, call cond_resched() from the scrub thread so that
we back out to the scheduler whenever necessary.
Reported-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sasha Levin <sashal@kernel.org>