Re: [PATCH] xfs_repair: fix totally broken unit conversion in directory invalidation

[Christoph Hellwig <hch@infradead.org>]

On Tue, Dec 17, 2019 at 08:24:02PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Your humble author forgot that xfs_dablk_t has the same units as
> xfs_fileoff_t, and totally screwed up the directory buffer invalidation
> loop in dir_binval.  Not only is there an off-by-one error in the loop
> conditional, but the unit conversions are wrong.

Can we kill off xfs_dablk_t?  I found the concept very, very confusing
when touching the dir code.

> --- a/libxfs/xfs_dir2.h
> +++ b/libxfs/xfs_dir2.h
> @@ -308,6 +308,16 @@ xfs_dir2_leaf_tail_p(struct xfs_da_geometry *geo, struct xfs_dir2_leaf *lp)
>  		  sizeof(struct xfs_dir2_leaf_tail));
>  }
>  
> +/*
> + * For a given dir/attr geometry and extent mapping record, walk every file
> + * offset block (xfs_dablk_t) in the mapping that corresponds to the start
> + * of a logical directory block (xfs_dir2_db_t).
> + */
> +#define for_each_xfs_bmap_dabno(geo, irec, dabno) \
> +	for ((dabno) = round_up((irec)->br_startoff, (geo)->fsbcount); \
> +	     (dabno) < (irec)->br_startoff + (irec)->br_blockcount; \
> +	     (dabno) += (geo)->fsbcount)

I think not having the magic for macro would be cleaner..

> +	xfs_dablk_t		dabno;
>  	int			error = 0;
>  
>  	if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
> @@ -1286,11 +1286,7 @@ dir_binval(
>  	geo = tp->t_mountp->m_dir_geo;
>  	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
>  	for_each_xfs_iext(ifp, &icur, &rec) {
> -		dabno = xfs_dir2_db_to_da(geo, rec.br_startoff +
> -				geo->fsbcount - 1);
> -		end_dabno = xfs_dir2_db_to_da(geo, rec.br_startoff +
> -				rec.br_blockcount);
> -		for (; dabno <= end_dabno; dabno += geo->fsbcount) {
> +		for_each_xfs_bmap_dabno(geo, &rec, dabno) {
>  			bp = NULL;
>  			error = -libxfs_da_get_buf(tp, ip, dabno, -2, &bp,
>  					whichfork);

But either way, the fix looks good.