Re: [PATCH 4/7] xfs: error out when a superblock buffer updates reduces the agcount

[Brian Foster <bfoster@redhat.com>]

On Mon, Sep 30, 2024 at 06:41:45PM +0200, Christoph Hellwig wrote:
> XFS currently does not support reducing the agcount, so error out if
> a logged sb buffer tries to shrink the agcount.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

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

>  fs/xfs/xfs_log_recover.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 03701409c7dcd6..3b5cd240bb62ef 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -3343,6 +3343,10 @@ xlog_recover_update_agcount(
>  	int				error;
>  
>  	xfs_sb_from_disk(&mp->m_sb, dsb);
> +	if (mp->m_sb.sb_agcount < old_agcount) {
> +		xfs_alert(mp, "Shrinking AG count in log recovery");
> +		return -EFSCORRUPTED;
> +	}
>  	error = xfs_initialize_perag(mp, old_agcount, mp->m_sb.sb_agcount,
>  			mp->m_sb.sb_dblocks, &mp->m_maxagi);
>  	if (error) {
> -- 
> 2.45.2
> 
>