Re: [PATCH 1/9] xfs: simplify mappedbno case from xfs_da_get_buf and xfs_da_read_buf

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Nov 16, 2019 at 07:22:06PM +0100, Christoph Hellwig wrote:
> Shortcut the creation of xfs_bmbt_irec and xfs_buf_map for the case
> where the callers passed an already mapped xfs_daddr_t.  This is in
> preparation for splitting these cases out entirely later.  Also reject
> the mappedbno case for xfs_da_reada_buf as no callers currently uses
> it and it will be removed soon.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks reasonable,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/libxfs/xfs_da_btree.c | 103 +++++++++++++++++------------------
>  1 file changed, 51 insertions(+), 52 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index 46b1c3fb305c..681fba5731c2 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -110,6 +110,13 @@ xfs_da_state_free(xfs_da_state_t *state)
>  	kmem_zone_free(xfs_da_state_zone, state);
>  }
>  
> +static inline int xfs_dabuf_nfsb(struct xfs_mount *mp, int whichfork)
> +{
> +	if (whichfork == XFS_DATA_FORK)
> +		return mp->m_dir_geo->fsbcount;
> +	return mp->m_attr_geo->fsbcount;
> +}
> +
>  void
>  xfs_da3_node_hdr_from_disk(
>  	struct xfs_mount		*mp,
> @@ -2570,7 +2577,7 @@ xfs_dabuf_map(
>  	int			*nmaps)
>  {
>  	struct xfs_mount	*mp = dp->i_mount;
> -	int			nfsb;
> +	int			nfsb = xfs_dabuf_nfsb(mp, whichfork);
>  	int			error = 0;
>  	struct xfs_bmbt_irec	irec;
>  	struct xfs_bmbt_irec	*irecs = &irec;
> @@ -2579,35 +2586,13 @@ xfs_dabuf_map(
>  	ASSERT(map && *map);
>  	ASSERT(*nmaps == 1);
>  
> -	if (whichfork == XFS_DATA_FORK)
> -		nfsb = mp->m_dir_geo->fsbcount;
> -	else
> -		nfsb = mp->m_attr_geo->fsbcount;
> -
> -	/*
> -	 * Caller doesn't have a mapping.  -2 means don't complain
> -	 * if we land in a hole.
> -	 */
> -	if (mappedbno == -1 || mappedbno == -2) {
> -		/*
> -		 * Optimize the one-block case.
> -		 */
> -		if (nfsb != 1)
> -			irecs = kmem_zalloc(sizeof(irec) * nfsb,
> -					    KM_NOFS);
> -
> -		nirecs = nfsb;
> -		error = xfs_bmapi_read(dp, (xfs_fileoff_t)bno, nfsb, irecs,
> -				       &nirecs, xfs_bmapi_aflag(whichfork));
> -		if (error)
> -			goto out;
> -	} else {
> -		irecs->br_startblock = XFS_DADDR_TO_FSB(mp, mappedbno);
> -		irecs->br_startoff = (xfs_fileoff_t)bno;
> -		irecs->br_blockcount = nfsb;
> -		irecs->br_state = 0;
> -		nirecs = 1;
> -	}
> +	if (nfsb != 1)
> +		irecs = kmem_zalloc(sizeof(irec) * nfsb, KM_NOFS);
> +	nirecs = nfsb;
> +	error = xfs_bmapi_read(dp, (xfs_fileoff_t)bno, nfsb, irecs,
> +			       &nirecs, xfs_bmapi_aflag(whichfork));
> +	if (error)
> +		goto out;
>  
>  	if (!xfs_da_map_covers_blocks(nirecs, irecs, bno, nfsb)) {
>  		/* Caller ok with no mapping. */
> @@ -2648,24 +2633,29 @@ xfs_dabuf_map(
>   */
>  int
>  xfs_da_get_buf(
> -	struct xfs_trans	*trans,
> +	struct xfs_trans	*tp,
>  	struct xfs_inode	*dp,
>  	xfs_dablk_t		bno,
>  	xfs_daddr_t		mappedbno,
>  	struct xfs_buf		**bpp,
>  	int			whichfork)
>  {
> +	struct xfs_mount	*mp = dp->i_mount;
>  	struct xfs_buf		*bp;
> -	struct xfs_buf_map	map;
> -	struct xfs_buf_map	*mapp;
> -	int			nmap;
> +	struct xfs_buf_map	map, *mapp = &map;
> +	int			nmap = 1;
>  	int			error;
>  
>  	*bpp = NULL;
> -	mapp = &map;
> -	nmap = 1;
> -	error = xfs_dabuf_map(dp, bno, mappedbno, whichfork,
> -				&mapp, &nmap);
> +
> +	if (mappedbno >= 0) {
> +		bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, mappedbno,
> +				XFS_FSB_TO_BB(mp,
> +					xfs_dabuf_nfsb(mp, whichfork)), 0);
> +		goto done;
> +	}
> +
> +	error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
>  	if (error) {
>  		/* mapping a hole is not an error, but we don't continue */
>  		if (error == -1)
> @@ -2673,12 +2663,12 @@ xfs_da_get_buf(
>  		goto out_free;
>  	}
>  
> -	bp = xfs_trans_get_buf_map(trans, dp->i_mount->m_ddev_targp,
> -				    mapp, nmap, 0);
> +	bp = xfs_trans_get_buf_map(tp, mp->m_ddev_targp, mapp, nmap, 0);
> +done:
>  	error = bp ? bp->b_error : -EIO;
>  	if (error) {
>  		if (bp)
> -			xfs_trans_brelse(trans, bp);
> +			xfs_trans_brelse(tp, bp);
>  		goto out_free;
>  	}
>  
> @@ -2696,7 +2686,7 @@ xfs_da_get_buf(
>   */
>  int
>  xfs_da_read_buf(
> -	struct xfs_trans	*trans,
> +	struct xfs_trans	*tp,
>  	struct xfs_inode	*dp,
>  	xfs_dablk_t		bno,
>  	xfs_daddr_t		mappedbno,
> @@ -2704,17 +2694,23 @@ xfs_da_read_buf(
>  	int			whichfork,
>  	const struct xfs_buf_ops *ops)
>  {
> +	struct xfs_mount	*mp = dp->i_mount;
>  	struct xfs_buf		*bp;
> -	struct xfs_buf_map	map;
> -	struct xfs_buf_map	*mapp;
> -	int			nmap;
> +	struct xfs_buf_map	map, *mapp = &map;
> +	int			nmap = 1;
>  	int			error;
>  
>  	*bpp = NULL;
> -	mapp = &map;
> -	nmap = 1;
> -	error = xfs_dabuf_map(dp, bno, mappedbno, whichfork,
> -				&mapp, &nmap);
> +
> +	if (mappedbno >= 0) {
> +		error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
> +				mappedbno, XFS_FSB_TO_BB(mp,
> +					xfs_dabuf_nfsb(mp, whichfork)),
> +				0, &bp, ops);
> +		goto done;
> +	}
> +
> +	error = xfs_dabuf_map(dp, bno, mappedbno, whichfork, &mapp, &nmap);
>  	if (error) {
>  		/* mapping a hole is not an error, but we don't continue */
>  		if (error == -1)
> @@ -2722,9 +2718,9 @@ xfs_da_read_buf(
>  		goto out_free;
>  	}
>  
> -	error = xfs_trans_read_buf_map(dp->i_mount, trans,
> -					dp->i_mount->m_ddev_targp,
> -					mapp, nmap, 0, &bp, ops);
> +	error = xfs_trans_read_buf_map(mp, tp, mp->m_ddev_targp, mapp, nmap, 0,
> +			&bp, ops);
> +done:
>  	if (error)
>  		goto out_free;
>  
> @@ -2756,6 +2752,9 @@ xfs_da_reada_buf(
>  	int			nmap;
>  	int			error;
>  
> +	if (mappedbno >= 0)
> +		return -EINVAL;
> +
>  	mapp = &map;
>  	nmap = 1;
>  	error = xfs_dabuf_map(dp, bno, mappedbno, whichfork,
> -- 
> 2.20.1
>