Re: [PATCH 3/4] xfs: remove the for_each_xbitmap_ helpers

[Brian Foster <bfoster@redhat.com>]

On Wed, Oct 09, 2019 at 09:49:22AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Remove the for_each_xbitmap_ macros in favor of proper iterator
> functions.  We'll soon be switching this data structure over to an
> interval tree implementation, which means that we can't allow callers to
> modify the bitmap during iteration without telling us.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/scrub/agheader_repair.c |   73 ++++++++++++++++++++++++----------------
>  fs/xfs/scrub/bitmap.c          |   59 ++++++++++++++++++++++++++++++++
>  fs/xfs/scrub/bitmap.h          |   22 ++++++++----
>  fs/xfs/scrub/repair.c          |   60 +++++++++++++++++----------------
>  4 files changed, 148 insertions(+), 66 deletions(-)
> 
> 
...
> diff --git a/fs/xfs/scrub/bitmap.h b/fs/xfs/scrub/bitmap.h
> index 900646b72de1..27fde5b4a753 100644
> --- a/fs/xfs/scrub/bitmap.h
> +++ b/fs/xfs/scrub/bitmap.h
...
> @@ -34,4 +27,19 @@ int xbitmap_set_btblocks(struct xbitmap *bitmap,
>  		struct xfs_btree_cur *cur);
>  uint64_t xbitmap_hweight(struct xbitmap *bitmap);
>  
> +/*
> + * Return codes for the bitmap iterator functions are 0 to continue iterating,
> + * and non-zero to stop iterating.  Any non-zero value will be passed up to the
> + * iteration caller.  The special value -ECANCELED can be used to stop
> + * iteration, because neither bitmap iterator ever generates that error code on
> + * its own.
> + */
> +typedef int (*xbitmap_walk_run_fn)(uint64_t start, uint64_t len, void *priv);
> +int xbitmap_iter_set(struct xbitmap *bitmap, xbitmap_walk_run_fn fn,
> +		void *priv);
> +
> +typedef int (*xbitmap_walk_bit_fn)(uint64_t bit, void *priv);
> +int xbitmap_iter_set_bits(struct xbitmap *bitmap, xbitmap_walk_bit_fn fn,
> +		void *priv);
> +

Somewhat of a nit, but I read "set" as a verb in the above function
names which tends to confuse me over what these functions do (i.e.
iterate bits, not set bits). Could we call them something a bit more
neutral, like xbitmap[_bit]_iter() perhaps? That aside the rest of the
patch looks Ok to me.

Brian

>  #endif	/* __XFS_SCRUB_BITMAP_H__ */
> diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
> index d41da4c44f10..588bc054db5c 100644
> --- a/fs/xfs/scrub/repair.c
> +++ b/fs/xfs/scrub/repair.c
> @@ -507,15 +507,21 @@ xrep_reap_invalidate_block(
>  	xfs_trans_binval(sc->tp, bp);
>  }
>  
> +struct xrep_reap_block {
> +	struct xfs_scrub		*sc;
> +	const struct xfs_owner_info	*oinfo;
> +	enum xfs_ag_resv_type		resv;
> +	unsigned int			deferred;
> +};
> +
>  /* Dispose of a single block. */
>  STATIC int
>  xrep_reap_block(
> -	struct xfs_scrub		*sc,
> -	xfs_fsblock_t			fsbno,
> -	const struct xfs_owner_info	*oinfo,
> -	enum xfs_ag_resv_type		resv,
> -	unsigned int			*deferred)
> +	uint64_t			fsbno,
> +	void				*priv)
>  {
> +	struct xrep_reap_block		*rb = priv;
> +	struct xfs_scrub		*sc = rb->sc;
>  	struct xfs_btree_cur		*cur;
>  	struct xfs_buf			*agf_bp = NULL;
>  	xfs_agnumber_t			agno;
> @@ -527,6 +533,10 @@ xrep_reap_block(
>  	agno = XFS_FSB_TO_AGNO(sc->mp, fsbno);
>  	agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno);
>  
> +	ASSERT(sc->ip != NULL || agno == sc->sa.agno);
> +
> +	trace_xrep_dispose_btree_extent(sc->mp, agno, agbno, 1);
> +
>  	/*
>  	 * If we are repairing per-inode metadata, we need to read in the AGF
>  	 * buffer.  Otherwise, we're repairing a per-AG structure, so reuse
> @@ -544,7 +554,8 @@ xrep_reap_block(
>  	cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf_bp, agno);
>  
>  	/* Can we find any other rmappings? */
> -	error = xfs_rmap_has_other_keys(cur, agbno, 1, oinfo, &has_other_rmap);
> +	error = xfs_rmap_has_other_keys(cur, agbno, 1, rb->oinfo,
> +			&has_other_rmap);
>  	xfs_btree_del_cursor(cur, error);
>  	if (error)
>  		goto out_free;
> @@ -563,8 +574,9 @@ xrep_reap_block(
>  	 * to run xfs_repair.
>  	 */
>  	if (has_other_rmap) {
> -		error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1, oinfo);
> -	} else if (resv == XFS_AG_RESV_AGFL) {
> +		error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1,
> +				rb->oinfo);
> +	} else if (rb->resv == XFS_AG_RESV_AGFL) {
>  		xrep_reap_invalidate_block(sc, fsbno);
>  		error = xrep_put_freelist(sc, agbno);
>  	} else {
> @@ -576,16 +588,16 @@ xrep_reap_block(
>  		 * reservation.
>  		 */
>  		xrep_reap_invalidate_block(sc, fsbno);
> -		__xfs_bmap_add_free(sc->tp, fsbno, 1, oinfo, true);
> -		(*deferred)++;
> -		need_roll = *deferred > 100;
> +		__xfs_bmap_add_free(sc->tp, fsbno, 1, rb->oinfo, true);
> +		rb->deferred++;
> +		need_roll = rb->deferred > 100;
>  	}
>  	if (agf_bp != sc->sa.agf_bp)
>  		xfs_trans_brelse(sc->tp, agf_bp);
>  	if (error || !need_roll)
>  		return error;
>  
> -	*deferred = 0;
> +	rb->deferred = 0;
>  	if (sc->ip)
>  		return xfs_trans_roll_inode(&sc->tp, sc->ip);
>  	return xrep_roll_ag_trans(sc);
> @@ -604,27 +616,17 @@ xrep_reap_extents(
>  	const struct xfs_owner_info	*oinfo,
>  	enum xfs_ag_resv_type		type)
>  {
> -	struct xbitmap_range		*bmr;
> -	struct xbitmap_range		*n;
> -	xfs_fsblock_t			fsbno;
> -	unsigned int			deferred = 0;
> +	struct xrep_reap_block		rb = {
> +		.sc			= sc,
> +		.oinfo			= oinfo,
> +		.resv			= type,
> +	};
>  	int				error = 0;
>  
>  	ASSERT(xfs_sb_version_hasrmapbt(&sc->mp->m_sb));
>  
> -	for_each_xbitmap_block(fsbno, bmr, n, bitmap) {
> -		ASSERT(sc->ip != NULL ||
> -		       XFS_FSB_TO_AGNO(sc->mp, fsbno) == sc->sa.agno);
> -		trace_xrep_dispose_btree_extent(sc->mp,
> -				XFS_FSB_TO_AGNO(sc->mp, fsbno),
> -				XFS_FSB_TO_AGBNO(sc->mp, fsbno), 1);
> -
> -		error = xrep_reap_block(sc, fsbno, oinfo, type, &deferred);
> -		if (error)
> -			break;
> -	}
> -
> -	if (error || deferred == 0)
> +	error = xbitmap_iter_set_bits(bitmap, xrep_reap_block, &rb);
> +	if (error || rb.deferred == 0)
>  		return error;
>  
>  	if (sc->ip)
>