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

[Dan Williams]

On Fri, Feb 28, 2020 at 6:05 AM Christoph Hellwig <hch at infradead.org> wrote:
>
> 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).

Understood. To be clear the plan we are marching to is knock down all
the known objections to the removal of the "experimental" designation.
reflink is on that list and so is per-file dax. The thought was that
pef-file dax was a nearer term goal than reflink.