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

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Apr 25, 2025 at 08:52:53AM +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.

If the log device is readonly, does that mean the filesystem gets
mounted norecovery too?  Your test might want to check that a dirty log
is not recovered even if the filesystem mounts.

--D

> Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
> ---
> 
> I will post a couple of xfstests to add coverage for these cases.
> 
>  fs/xfs/xfs_super.c | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index b2dd0c0bf509..d7ac1654bc80 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -380,10 +380,14 @@ 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 = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
> +	if (!xfs_is_readonly(mp))
> +		mode |= BLK_OPEN_WRITE;
> +
> +	*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 +1973,20 @@ 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
>