linux-kernel - Re: [PATCH v2] xfs: allow ro mounts if rtdev or logdev are read-only

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Message-ID: <veeiqwim6lrjh7wqtnhcguh5ukxcl74lkzloqxthbh5e6rjie7@euq7b7ksqdqr>
Date: Wed, 30 Apr 2025 11:36:42 +0200
From: Carlos Maiolino <cem@...nel.org>
To: Hans Holmberg <Hans.Holmberg@....com>
Cc: Dave Chinner <david@...morbit.com>, 
	"Darrick J . Wong" <djwong@...nel.org>, hch <hch@....de>, 
	"linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] xfs: allow ro mounts if rtdev or logdev are read-only

On Wed, Apr 30, 2025 at 08:35:34AM +0000, Hans Holmberg wrote:
> Allow read-only mounts on rtdevs and logdevs that are marked as
> read-only and make sure those mounts can't be remounted read-write.
> 
> Use the sb_open_mode helper to make sure that we don't try to open
> devices with write access enabled for read-only mounts.
> 
> Signed-off-by: Hans Holmberg <hans.holmberg@....com>

This looks good, thanks Hans!

Reviewed-by: Carlos Maiolino <cmaiolino@...hat.com>

> ---
> 
> Changes since v1:
>  - Switched to using the sb_open_mode helper that does exactly
>    what we want.
> 
>  fs/xfs/xfs_super.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index b2dd0c0bf509..5e456a6073ca 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -380,10 +380,11 @@ xfs_blkdev_get(
>  	struct file		**bdev_filep)
>  {
>  	int			error = 0;
> +	blk_mode_t		mode;
> 
> -	*bdev_filep = bdev_file_open_by_path(name,
> -		BLK_OPEN_READ | BLK_OPEN_WRITE | BLK_OPEN_RESTRICT_WRITES,
> -		mp->m_super, &fs_holder_ops);
> +	mode = sb_open_mode(mp->m_super->s_flags);
> +	*bdev_filep = bdev_file_open_by_path(name, mode,
> +			mp->m_super, &fs_holder_ops);
>  	if (IS_ERR(*bdev_filep)) {
>  		error = PTR_ERR(*bdev_filep);
>  		*bdev_filep = NULL;
> @@ -1969,6 +1970,20 @@ xfs_remount_rw(
>  	struct xfs_sb		*sbp = &mp->m_sb;
>  	int error;
> 
> +	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp &&
> +	    bdev_read_only(mp->m_logdev_targp->bt_bdev)) {
> +		xfs_warn(mp,
> +			"ro->rw transition prohibited by read-only logdev");
> +		return -EACCES;
> +	}
> +
> +	if (mp->m_rtdev_targp &&
> +	    bdev_read_only(mp->m_rtdev_targp->bt_bdev)) {
> +		xfs_warn(mp,
> +			"ro->rw transition prohibited by read-only rtdev");
> +		return -EACCES;
> +	}
> +
>  	if (xfs_has_norecovery(mp)) {
>  		xfs_warn(mp,
>  			"ro->rw transition prohibited on norecovery mount");
> --
> 2.34.1
>