Re: [PATCH v3 01/11] pagemap: Introduce ->memory_failure()

[Christoph Hellwig]

On Wed, Mar 24, 2021 at 09:37:01AM -0700, Dan Williams wrote:
> > Eww.  As I said I think the right way is that the file system (or
> > other consumer) can register a set of callbacks for opening the device.
> 
> How does that solve the problem of the driver being notified of all
> pfn failure events?

Ok, I probably just showed I need to spend more time looking at
your proposal vs the actual code..

Don't we have a proper way how one of the nvdimm layers own a
spefific memory range and call directly into that instead of through
a notifier?

> Today pmem only finds out about the ones that are
> notified via native x86 machine check error handling via a notifier
> (yes "firmware-first" error handling fails to do the right thing for
> the pmem driver),

Did any kind of firmware-first error handling ever get anything
right?  I wish people would have learned that by now.

> or the ones that are eventually reported via address
> range scrub, but only for the nvdimms that implement range scrubbing.
> memory_failure() seems a reasonable catch all point to route pfn
> failure events, in an arch independent way, to interested drivers.

Yeah.

> I'm fine swapping out dax_device blocking_notiier chains for your
> proposal, but that does not address all the proposed reworks in my
> list which are:
> 
> - delete "drivers/acpi/nfit/mce.c"
> 
> - teach memory_failure() to be able to communicate range failure
> 
> - enable memory_failure() to defer to a filesystem that can say
> "critical metadata is impacted, no point in trying to do file-by-file
> isolation, bring the whole fs down".

This all sounds sensible.