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

Christoph Hellwig
2021-10-22T05:38:13Z

On Thu, Oct 21, 2021 at 06:58:17PM -0700, Darrick J. Wong wrote:
> 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.
>
> Why would data recovery after a media error ever be considered a
> fast/hot path?

Not sure what you're replying to (the text is from me, the mail you are
repling to is fom Jane), but my point is that the read/write
got path should not be overloaded with data recovery.

> A normal read/write to a fsdax file would not pass the
> flag, which skips the poison checking with whatever MCE consequences
> that has, right?

Exactly!

> pwritev2(..., RWF_RECOVER_DATA) should be infrequent enough that
> carefully stepping around dax_direct_access only has to be faster than
> restoring from backup, I hope?

Yes. And thus be kept as separate as possible.