[PATCH 1/3] nvme-core: improve avoiding false remove namespace

[Christoph Hellwig]

On Wed, Aug 19, 2020 at 09:33:22PM -0700, Sagi Grimberg wrote:
> We really need to take a step back here, I really don't like how
> we are growing implicit assumptions on how statuses are interpreted.
>
> Why don't we remove the -ENODEV error propagation back and instead
> take care of it in the specific call-sites where we want to ignore
> errors with proper quirks?

So the one thing I'm not even sure about is if just ignoring the
errors was a good idea to start with.  They obviously are if we just
did a rescan and did run into an error while rescanning a namespace
that didn't change.  But what if it actually did change?

So I think a logic like in this patch kinda makes sense, but I think
we also need to retry and scan again on these kinds of errors.  Btw,
did you ever actually see -ENOMEM in practice?  With the small
allocations that we do it really should not happen normally, so
special casing for it always felt a little strange.

FYI, I've started rebasing various bits of work I've done to start
untangling the mess.  Here is my current WIP, which in this form
is completely untested:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/nvme-scanning-cleanup