Re: [PATCH 4/6] dm,dax,pmem: prepare dax_copy_to/from_iter() APIs with DAXDEV_F_RECOVERY

Christoph Hellwig
2021-10-22T05:34:12Z

On Fri, Oct 22, 2021 at 12:49:15AM +0000, Jane Chu wrote:
> I've looked through your "futher decouple DAX from block devices" series
> and likes the use of xarray in place of the host hash list.
> Which upstream version is the series based upon?
> If it's based on your development repo, I'd be happy to take a clone
> and rebase my patches on yours if you provide a link. Please let me
> know the best way to cooperate.

It is based on linux-next from when it was posted. A git tree is here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dax-block-cleanup

> That said, I'm unclear at what you're trying to suggest with respect
> to the 'DAXDEV_F_RECOVERY' flag. The flag came from upper dax-fs
> call stack to the dm target layer, and the dm targets are equipped
> with handling pmem driver specific task, so it appears that the flag
> would need to be passed down to the native pmem layer, right?
> Am I totally missing your point?

We'll need to pass it through (assuming we want to keep supporting
dm, see the recent discussion with Dan).

FYI, here is a sketch where I'd like to move to, but this isn't properly
tested yet:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dax-devirtualize

To support something like DAXDEV_F_RECOVERYwe'd need a separate
dax_operations methods. Which to me suggest it probably should be
a different operation (fallocate / ioctl / etc) as Darrick did earlier.