Re: [PATCH 0/2] xfs: fix up some reflink+dax interactions

[Eric Sandeen <sandeen@redhat.com>]

On 12/1/20 1:10 PM, Eric Sandeen wrote:
> dax behavior has changed semi-recently, most notably that per-inode dax
> flags are back, which opens the possibility of dax-capable files existing on
> reflink-capable filesystems.
> 
> While we still have a reflink-vs-dax-on-the-same-file incompatibilty, and for
> the most part this is handled correctly, there are a couple of known issues:
> 
> 1) xfs_dinode_verify will trap an inode with reflink+dax flags as corrupted;
>    this needs to be removed, because we actually can get into this state today,
>    and eventually that state will be supported in future kernels.
> 
> 2) (more RFC) until we actually support reflink+dax files, perhaps we should
>    prevent the flags from co-existing in a kernel that cannot support both
>    states.  patch 2 stops us from reflinking files with the dax flag set,
>    whether or not the file is actually "in the CPU direct access state"
> 
> -Eric

Also yes I owe xfstests for these but wanted to see if the patches fly, first.

-Eric