Re: [dm-devel] [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag

Christoph Hellwig
2021-10-22T05:36:51Z

On Fri, Oct 22, 2021 at 01:37:28AM +0000, Jane Chu wrote:
> On 10/21/2021 4:31 AM, Christoph Hellwig wrote:
> > Looking over the series I have serious doubts that overloading the
> > slow path clear poison operation over the fast path read/write
> > path is such a great idea.
> >
>
> Understood, sounds like a concern on principle. But it seems to me
> that the task of recovery overlaps with the normal write operation
> on the write part. Without overloading some write operation for
> 'recovery', I guess we'll need to come up with a new userland
> command coupled with a new dax API ->clear_poison and propagate the
> new API support to each dm targets that support dax which, again,
> is an idea that sounds too bulky if I recall Dan's earlier rejection
> correctly.

When I wrote the above I mostly thought about the in-kernel API, that
is use a separate method. But reading your mail and thinking about
this a bit more I'm actually less and less sure that overloading
pwritev2 and preadv2 with this at the syscall level makes sense either.
read/write are our I/O fast path. We really should not overload the
core of the VFS with error recovery for a broken hardware interface.