linux-ext4 - [RFC PATCH v2 4/8] ext4: Use dax_is

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Date: Tue, 30 Jan 2024 11:52:51 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Dan Williams <dan.j.williams@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-mm@...ck.org,
	linux-arch@...r.kernel.org,
	Matthew Wilcox <willy@...radead.org>,
	Arnd Bergmann <arnd@...db.de>,
	Russell King <linux@...linux.org.uk>,
	nvdimm@...ts.linux.dev,
	linux-cxl@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [RFC PATCH v2 4/8] ext4: Use dax_is_supported()

Use dax_is_supported() to validate whether the architecture has
virtually aliased data caches at mount time. Mount fails 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@...icios.com>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: linux-ext4@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-arch@...r.kernel.org
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Russell King <linux@...linux.org.uk>
Cc: nvdimm@...ts.linux.dev
Cc: linux-cxl@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
---
 fs/ext4/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c5fcf377ab1f..f2c11ae3ec29 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4743,7 +4743,10 @@ static int ext4_check_feature_compatibility(struct super_block *sb,
 	}
 
 	if (sbi->s_mount_opt & EXT4_MOUNT_DAX_ALWAYS) {
-		if (ext4_has_feature_inline_data(sb)) {
+		if (!dax_is_supported()) {
+			ext4_msg(sb, KERN_ERR, "DAX unsupported by architecture.");
+			return -EINVAL;
+		} else if (ext4_has_feature_inline_data(sb)) {
 			ext4_msg(sb, KERN_ERR, "Cannot use DAX on a filesystem"
 					" that may contain inline data");
 			return -EINVAL;
-- 
2.39.2