RE: [PATCH v4 09/12] nvdimm/pmem: Cleanup alloc_dax() error handling

[Dan Williams <dan.j.williams@intel.com>]

Mathieu Desnoyers wrote:
> Now that alloc_dax() returns ERR_PTR(-EOPNOTSUPP) rather than NULL,
> the callers do not have to handle NULL return values anymore.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Alasdair Kergon <agk@redhat.com>
> Cc: Mike Snitzer <snitzer@kernel.org>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-cxl@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-xfs@vger.kernel.org
> Cc: dm-devel@lists.linux.dev
> Cc: nvdimm@lists.linux.dev
> ---
>  drivers/nvdimm/pmem.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index f1d9f5c6dbac..e9898457a7bd 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -558,8 +558,8 @@ static int pmem_attach_disk(struct device *dev,
>  	disk->bb = &pmem->bb;
>  
>  	dax_dev = alloc_dax(pmem, &pmem_dax_ops);
> -	if (IS_ERR_OR_NULL(dax_dev)) {
> -		rc = IS_ERR(dax_dev) ? PTR_ERR(dax_dev) : -EOPNOTSUPP;
> +	if (IS_ERR(dax_dev)) {
> +		rc = PTR_ERR(dax_dev);

Oh... I see you cleanup what I was talking about later in the series.

For my taste I don't like to see tech-debt added and then removed later
in the series. The whole series would appear to get smaller by removing
the alloc_dax() returning NULL case from the beginning, and then doing
the EOPNOTSUPP fixups.

...repeat this comment for patch 10, 11, 12.