linux-ext4 - Re: [RFC PATCH v2 3/8] ext2: Use dax_is

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Date: Tue, 30 Jan 2024 22:40:06 +0100
From: Jan Kara <jack@...e.cz>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-kernel@...r.kernel.org,
	Jan Kara <jack@...e.com>, 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: Re: [RFC PATCH v2 3/8] ext2: Use dax_is_supported()

On Tue 30-01-24 11:52:50, Mathieu Desnoyers wrote:
> 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: Jan Kara <jack@...e.com>
> 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

OK, yeah, this is better than v1. Feel free to add:

Acked-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext2/super.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext2/super.c b/fs/ext2/super.c
> index 01f9addc8b1f..30ff57d47ed4 100644
> --- a/fs/ext2/super.c
> +++ b/fs/ext2/super.c
> @@ -955,7 +955,11 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
>  	blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
>  
>  	if (test_opt(sb, DAX)) {
> -		if (!sbi->s_daxdev) {
> +		if (!dax_is_supported()) {
> +			ext2_msg(sb, KERN_ERR,
> +				"DAX unsupported by architecture. Turning off DAX.");
> +			clear_opt(sbi->s_mount_opt, DAX);
> +		} else if (!sbi->s_daxdev) {
>  			ext2_msg(sb, KERN_ERR,
>  				"DAX unsupported by block device. Turning off DAX.");
>  			clear_opt(sbi->s_mount_opt, DAX);
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR