Re: [PATCH v5 13/17] xfs: mount api - add xfs_reconfigure()

[Brian Foster <bfoster@redhat.com>]

On Wed, Oct 09, 2019 at 07:31:19PM +0800, Ian Kent wrote:
> Add the fs_context_operations method .reconfigure that performs
> remount validation as previously done by the super_operations
> .remount_fs method.
> 
> Signed-off-by: Ian Kent <raven@themaw.net>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_super.c |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 7e634706626b..230b0e2a184c 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1544,6 +1544,67 @@ xfs_fs_remount(
>  	return 0;
>  }
>  
> +/*
> + * Logically we would return an error here to prevent users
> + * from believing they might have changed mount options using
> + * remount which can't be changed.
> + *
> + * But unfortunately mount(8) adds all options from mtab and
> + * fstab to the mount arguments in some cases so we can't
> + * blindly reject options, but have to check for each specified
> + * option if it actually differs from the currently set option
> + * and only reject it if that's the case.
> + *
> + * Until that is implemented we return success for every remount
> + * request, and silently ignore all options that we can't actually
> + * change.
> + */
> +STATIC int
> +xfs_reconfigure(
> +	struct fs_context *fc)
> +{
> +	struct xfs_fs_context	*ctx = fc->fs_private;
> +	struct xfs_mount	*mp = XFS_M(fc->root->d_sb);
> +	struct xfs_mount        *new_mp = fc->s_fs_info;
> +	xfs_sb_t		*sbp = &mp->m_sb;
> +	int			flags = fc->sb_flags;
> +	int			error;
> +
> +	error = xfs_validate_params(new_mp, ctx, false);
> +	if (error)
> +		return error;
> +
> +	/* inode32 -> inode64 */
> +	if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) &&
> +	    !(new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) {
> +		mp->m_flags &= ~XFS_MOUNT_SMALL_INUMS;
> +		mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
> +	}
> +
> +	/* inode64 -> inode32 */
> +	if (!(mp->m_flags & XFS_MOUNT_SMALL_INUMS) &&
> +	    (new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) {
> +		mp->m_flags |= XFS_MOUNT_SMALL_INUMS;
> +		mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
> +	}
> +
> +	/* ro -> rw */
> +	if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(flags & SB_RDONLY)) {
> +		error = xfs_remount_rw(mp);
> +		if (error)
> +			return error;
> +	}
> +
> +	/* rw -> ro */
> +	if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (flags & SB_RDONLY)) {
> +		error = xfs_remount_ro(mp);
> +		if (error)
> +			return error;
> +	}
> +
> +	return 0;
> +}
> +
>  /*
>   * Second stage of a freeze. The data is already frozen so we only
>   * need to take care of the metadata. Once that's done sync the superblock
> @@ -2069,6 +2130,7 @@ static const struct super_operations xfs_super_operations = {
>  static const struct fs_context_operations xfs_context_ops = {
>  	.parse_param = xfs_parse_param,
>  	.get_tree    = xfs_get_tree,
> +	.reconfigure = xfs_reconfigure,
>  };
>  
>  static struct file_system_type xfs_fs_type = {
>