linux-kernel - [RFC PATCH v2 2/8] erofs: Use dax_is

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Message-Id: <20240130165255.212591-3-mathieu.desnoyers@efficios.com>
Date: Tue, 30 Jan 2024 11:52:49 -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>,
	Gao Xiang <xiang@...nel.org>,
	Chao Yu <chao@...nel.org>,
	Yue Hu <huyue2@...lpad.com>,
	Jeffle Xu <jefflexu@...ux.alibaba.com>,
	linux-erofs@...ts.ozlabs.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 2/8] erofs: Use dax_is_supported()

Use dax_is_supported() to validate whether the architecture has
virtually aliased data caches at mount time. Print an error and 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@...icios.com>
Cc: Gao Xiang <xiang@...nel.org>
Cc: Chao Yu <chao@...nel.org>
Cc: Yue Hu <huyue2@...lpad.com>
Cc: Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc: linux-erofs@...ts.ozlabs.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/erofs/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 3789d6224513..82e569bd5889 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -644,7 +644,10 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 	}
 
 	if (test_opt(&sbi->opt, DAX_ALWAYS)) {
-		if (!sbi->dax_dev) {
+		if (!dax_is_supported()) {
+			errorfc(fc, "DAX unsupported by architecture. Turning off DAX.");
+			clear_opt(&sbi->opt, DAX_ALWAYS);
+		} else if (!sbi->dax_dev) {
 			errorfc(fc, "DAX unsupported by block device. Turning off DAX.");
 			clear_opt(&sbi->opt, DAX_ALWAYS);
 		} else if (sbi->blkszbits != PAGE_SHIFT) {
-- 
2.39.2