Re: [PATCH] dcssblk: Mark DAX broken

[Alexander Gordeev <agordeev@linux.ibm.com>]

On Tue, Sep 24, 2024 at 03:59:08PM -0700, Dan Williams wrote:

Hi Dan,

> The dcssblk driver has long needed special case supoprt to enable
> limited dax operation, so called CONFIG_FS_DAX_LIMITED. This mode
> works around the incomplete support for ZONE_DEVICE on s390 by forgoing
> the ability of dax-mapped pages to support GUP.
> 
> Now, pending cleanups to fsdax that fix its reference counting [1] depend on
> the ability of all dax drivers to supply ZONE_DEVICE pages.
> 
> To allow that work to move forward, dax support needs to be paused for
> dcssblk until ZONE_DEVICE support arrives. That work has been known for
> a few years [2], and the removal of "pte_devmap" requirements [3] makes the
> conversion easier.
> 
> For now, place the support behind CONFIG_BROKEN, and remove PFN_SPECIAL
> (dcssblk was the only user).
> 
> Link: http://lore.kernel.org/cover.9f0e45d52f5cff58807831b6b867084d0b14b61c.1725941415.git-series.apopple@nvidia.com [1]
> Link: http://lore.kernel.org/20210820210318.187742e8@thinkpad/ [2]
> Link: http://lore.kernel.org/4511465a4f8429f45e2ac70d2e65dc5e1df1eb47.1725941415.git-series.apopple@nvidia.com [3]
...
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/s390/block/Kconfig   |   12 ++++++++++--
>  drivers/s390/block/dcssblk.c |   26 +++++++++++++++++---------
>  fs/Kconfig                   |    9 +--------
>  fs/dax.c                     |   12 ------------
>  include/linux/pfn_t.h        |   15 ---------------
>  mm/memory.c                  |    2 --
>  mm/memremap.c                |    4 ----
>  7 files changed, 28 insertions(+), 52 deletions(-)

...

I guess you want to remove dcssblk from Documentation/filesystems/dax.rst.
Gerald is back from vacation on Monday and he will likely comment on this.

Tested-by: Alexander Gordeev <agordeev@linux.ibm.com>

Thanks!