[RFC PATCH 7/7] xfs: Use dax_is_supported()

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Use dax_is_supported() to validate whether the architecture has
virtually aliased caches at mount time.

This is relevant for architectures which require a dynamic check
to validate whether they have virtually aliased data caches
(ARCH_HAS_CACHE_ALIASING_DYNAMIC=y).

Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Chandan Babu R <chandan.babu@oracle.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-arch@vger.kernel.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: nvdimm@lists.linux.dev
Cc: linux-cxl@vger.kernel.org
---
 fs/xfs/xfs_super.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 764304595e8b..b27ecb11db66 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1376,14 +1376,22 @@ xfs_fs_parse_param(
 	case Opt_nodiscard:
 		parsing_mp->m_features &= ~XFS_FEAT_DISCARD;
 		return 0;
-#ifdef CONFIG_FS_DAX
 	case Opt_dax:
-		xfs_mount_set_dax_mode(parsing_mp, XFS_DAX_ALWAYS);
-		return 0;
+		if (dax_is_supported()) {
+			xfs_mount_set_dax_mode(parsing_mp, XFS_DAX_ALWAYS);
+			return 0;
+		} else {
+			xfs_warn(parsing_mp, "dax option not supported.");
+			return -EINVAL;
+		}
 	case Opt_dax_enum:
-		xfs_mount_set_dax_mode(parsing_mp, result.uint_32);
-		return 0;
-#endif
+		if (dax_is_supported()) {
+			xfs_mount_set_dax_mode(parsing_mp, result.uint_32);
+			return 0;
+		} else {
+			xfs_warn(parsing_mp, "dax option not supported.");
+			return -EINVAL;
+		}
 	/* Following mount options will be removed in September 2025 */
 	case Opt_ikeep:
 		xfs_fs_warn_deprecated(fc, param, XFS_FEAT_IKEEP, true);
-- 
2.39.2