Re: block: be more careful about status in __bio_chain_endio

From: Christoph Hellwig
Date: Wed Jun 12 2019 - 03:06:21 EST

On Tue, Jun 11, 2019 at 10:56:42PM -0400, John Dorminy wrote:
> I believe the second of these might, but is not guaranteed to,
> preserve the first error observed in a child; I believe if you want to
> definitely save the first error you need an atomic.

Is there any reason not to simply use a cmpxchg? Yes, it is a
relatively expensive operation, but once we are chaining bios we are out
of the super hot path anyway. We do something similar in xfs and iomap