[RFC PATCH v2 5/8] fuse: Use dax_is_supported()

[Mathieu Desnoyers]

Use dax_is_supported() to validate whether the architecture has
virtually aliased data caches at mount time. Silently disable
DAX if dax=always is requested as a mount option on an architecture
which does not support DAX.

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

Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: nvdimm@xxxxxxxxxxxxxxx
Cc: linux-cxl@xxxxxxxxxxxxxxx
---
 fs/fuse/dax.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 12ef91d170bb..36e1c1abbf8e 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1336,6 +1336,13 @@ static bool fuse_should_enable_dax(struct inode *inode, unsigned int flags)
 	if (dax_mode == FUSE_DAX_NEVER)
 		return false;
 
+	/*
+	 * Silently fallback to 'never' mode if the architecture does
+	 * not support DAX.
+	 */
+	if (!dax_is_supported())
+		return false;
+
 	/*
 	 * fc->dax may be NULL in 'inode' mode when filesystem device doesn't
 	 * support DAX, in which case it will silently fallback to 'never' mode.
-- 
2.39.2