[dm-devel] [PATCH v5 2/8] drivers/pmem: Allow pmem_clear_poison() to accept arbitrary offset and len

[Christoph Hellwig]

On Thu, Feb 27, 2020 at 07:28:41PM -0800, Dan Williams wrote:
> "don't perform generic memory-error-handling, there's an fs that owns
> this daxdev and wants to disposition errors". The fs/dax.c
> infrastructure that sets up ->index and ->mapping would still need to
> be there for ext4 until its ready to take on the same responsibility.
> Last I checked the ext4 reverse mapping implementation was not as
> capable as XFS. This goes back to why the initial design avoided
> relying on not universally available / stable reverse-mapping
> facilities and opted for extending the generic mm/memory-failure.c
> implementation.

The important but is that we stop using ->index and ->mapping when XFS
is used as that enables using DAX+reflinks, which actually is the most
requested DAX feature on XFS (way more than silly runtime flag switches
for example).