RE: [PATCH v4 04/12] dcssblk: Handle alloc_dax() -EOPNOTSUPP failure

Dan Williams
2024-02-08T21:36:06Z

Mathieu Desnoyers wrote:
> In preparation for checking whether the architecture has data cache
> aliasing within alloc_dax(), modify the error handling of dcssblk
> dcssblk_add_store() to handle alloc_dax() -EOPNOTSUPP failures.
>
> Considering that s390 is not a data cache aliasing architecture,
> and considering that DCSSBLK selects DAX, a return value of -EOPNOTSUPP
> from alloc_dax() should make dcssblk_add_store() fail.
>
> For the transition, consider that alloc_dax() returning NULL is the
> same as returning -EOPNOTSUPP.
>
> Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> 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
> Cc: linux-s390@vger.kernel.org
> ---
> drivers/s390/block/dcssblk.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 4b7ecd4fd431..a3010849bfed 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -549,6 +549,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
> int rc, i, j, num_of_segments;
> struct dcssblk_dev_info *dev_info;
> struct segment_info *seg_info, *temp;
> + struct dax_device *dax_dev;
> char *local_buf;
> unsigned long seg_byte_size;
>
> @@ -677,13 +678,13 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
> if (rc)
> goto put_dev;
>
> - dev_info->dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops);
> - if (IS_ERR(dev_info->dax_dev)) {
> - rc = PTR_ERR(dev_info->dax_dev);
> - dev_info->dax_dev = NULL;
> + dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops);
> + if (IS_ERR_OR_NULL(dax_dev)) {
> + rc = IS_ERR(dax_dev) ? PTR_ERR(dax_dev) : -EOPNOTSUPP;

Just another "ditto" on alloc_dax() returning NULL so that the ternary
can be removed, but otherwise this looks good.