Re: [PATCH] xfs: count free space btree blocks when scrubbing pre-lazysbcount fses

[Brian Foster <bfoster@redhat.com>]

On Mon, Apr 26, 2021 at 08:02:32PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Since agf_btreeblks didn't exist before the lazysbcount feature, the fs
> summary count scrubber needs to walk the free space btrees to determine
> the amount of space being used by those btrees.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---

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

> Note: I /think/ the four patches on the list right now fix all the
> obvious problems with !lazysbcount filesystems, except for xfs/49[12]
> which fuzz the summary counters.
> ---
>  fs/xfs/scrub/fscounters.c |   37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/fs/xfs/scrub/fscounters.c b/fs/xfs/scrub/fscounters.c
> index 318b81c0f90d..87476a00de9d 100644
> --- a/fs/xfs/scrub/fscounters.c
> +++ b/fs/xfs/scrub/fscounters.c
> @@ -13,6 +13,7 @@
>  #include "xfs_alloc.h"
>  #include "xfs_ialloc.h"
>  #include "xfs_health.h"
> +#include "xfs_btree.h"
>  #include "scrub/scrub.h"
>  #include "scrub/common.h"
>  #include "scrub/trace.h"
> @@ -143,6 +144,35 @@ xchk_setup_fscounters(
>  	return xchk_trans_alloc(sc, 0);
>  }
>  
> +/* Count free space btree blocks manually for pre-lazysbcount filesystems. */
> +static int
> +xchk_fscount_btreeblks(
> +	struct xfs_scrub	*sc,
> +	struct xchk_fscounters	*fsc,
> +	xfs_agnumber_t		agno)
> +{
> +	xfs_extlen_t		blocks;
> +	int			error;
> +
> +	error = xchk_ag_init(sc, agno, &sc->sa);
> +	if (error)
> +		return error;
> +
> +	error = xfs_btree_count_blocks(sc->sa.bno_cur, &blocks);
> +	if (error)
> +		goto out_free;
> +	fsc->fdblocks += blocks - 1;
> +
> +	error = xfs_btree_count_blocks(sc->sa.cnt_cur, &blocks);
> +	if (error)
> +		goto out_free;
> +	fsc->fdblocks += blocks - 1;
> +
> +out_free:
> +	xchk_ag_free(sc, &sc->sa);
> +	return error;
> +}
> +
>  /*
>   * Calculate what the global in-core counters ought to be from the incore
>   * per-AG structure.  Callers can compare this to the actual in-core counters
> @@ -184,6 +214,13 @@ xchk_fscount_aggregate_agcounts(
>  		fsc->fdblocks += pag->pagf_flcount;
>  		if (xfs_sb_version_haslazysbcount(&sc->mp->m_sb))
>  			fsc->fdblocks += pag->pagf_btreeblks;
> +		else {
> +			error = xchk_fscount_btreeblks(sc, fsc, agno);
> +			if (error) {
> +				xfs_perag_put(pag);
> +				break;
> +			}
> +		}
>  
>  		/*
>  		 * Per-AG reservations are taken out of the incore counters,
>