Re: [PATCH 4/6] xfs: introduce xfs_bmapi_remap

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

On Mon, Apr 03, 2017 at 02:18:31PM +0200, Christoph Hellwig wrote:
> Add a new helper to be used for reflink extent list additions instead of
> funneling them through xfs_bmapi_write and overloading the firstblock
> member in struct xfs_bmalloca and struct xfs_alloc_args.
> 
> With some small changes to xfs_bmap_remap_alloc this also means we do
> not need a xfs_bmalloca structure for this case at all.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 152 +++++++++++++++++++++++++++++++++--------------
>  1 file changed, 107 insertions(+), 45 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index d404dee7ede4..caadfe27af39 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3862,11 +3862,12 @@ xfs_bmap_btalloc(
>   */
>  STATIC int
>  xfs_bmap_remap_alloc(
> -	struct xfs_bmalloca	*ap)
> +	struct xfs_trans	*tp,
> +	struct xfs_inode	*ip,
> +	xfs_fsblock_t		startblock,
> +	xfs_extlen_t		length)

Why change all this if the next patch removes the whole function except:

ip->i_d.di_nblocks += length;
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

Wouldn't it make more sense to have this patch add _bmapi_remap (as it
appears in the next patch) and change the callers to use it; and then
the next patch removes the old _bmap_remap_alloc and its callers?

>  {
> -	struct xfs_trans	*tp = ap->tp;
>  	struct xfs_mount	*mp = tp->t_mountp;
> -	xfs_fsblock_t		bno;
>  	struct xfs_alloc_arg	args;
>  	int			error;
>  
> @@ -3875,24 +3876,24 @@ xfs_bmap_remap_alloc(
>  	 * and handle a silent filesystem corruption rather than crashing.
>  	 */
>  	memset(&args, 0, sizeof(struct xfs_alloc_arg));
> -	args.tp = ap->tp;
> -	args.mp = ap->tp->t_mountp;
> -	bno = *ap->firstblock;
> -	args.agno = XFS_FSB_TO_AGNO(mp, bno);
> -	args.agbno = XFS_FSB_TO_AGBNO(mp, bno);
> +	args.tp = tp;
> +	args.mp = mp;
> +	args.agno = XFS_FSB_TO_AGNO(mp, startblock);
> +	args.agbno = XFS_FSB_TO_AGBNO(mp, startblock);
> +
>  	if (args.agno >= mp->m_sb.sb_agcount ||
>  	    args.agbno >= mp->m_sb.sb_agblocks)
>  		return -EFSCORRUPTED;
>  
>  	/* "Allocate" the extent from the range we passed in. */
> -	trace_xfs_bmap_remap_alloc(ap->ip, *ap->firstblock, ap->length);
> -	ap->blkno = bno;
> -	ap->ip->i_d.di_nblocks += ap->length;
> -	xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
> +	trace_xfs_bmap_remap_alloc(ip, startblock, length);
> +
> +	ip->i_d.di_nblocks += length;
> +	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
>  
>  	/* Fix the freelist, like a real allocator does. */
> -	args.datatype = ap->datatype;
> -	args.pag = xfs_perag_get(args.mp, args.agno);
> +	args.datatype = XFS_ALLOC_USERDATA | XFS_ALLOC_NOBUSY;
> +	args.pag = xfs_perag_get(mp, args.agno);
>  	ASSERT(args.pag);
>  
>  	/*
> @@ -3905,7 +3906,7 @@ xfs_bmap_remap_alloc(
>  	error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING);
>  	xfs_perag_put(args.pag);
>  	if (error)
> -		trace_xfs_bmap_remap_alloc_error(ap->ip, error, _RET_IP_);
> +		trace_xfs_bmap_remap_alloc_error(ip, error, _RET_IP_);
>  	return error;
>  }
>  
> @@ -3917,8 +3918,6 @@ STATIC int
>  xfs_bmap_alloc(
>  	struct xfs_bmalloca	*ap)	/* bmap alloc argument struct */
>  {
> -	if (ap->flags & XFS_BMAPI_REMAP)
> -		return xfs_bmap_remap_alloc(ap);
>  	if (XFS_IS_REALTIME_INODE(ap->ip) &&
>  	    xfs_alloc_is_userdata(ap->datatype))
>  		return xfs_bmap_rtalloc(ap);
> @@ -4554,9 +4553,7 @@ xfs_bmapi_write(
>  	ASSERT(len > 0);
>  	ASSERT(XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_LOCAL);
>  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> -	ASSERT(!(flags & XFS_BMAPI_REMAP) || whichfork == XFS_DATA_FORK);
> -	ASSERT(!(flags & XFS_BMAPI_PREALLOC) || !(flags & XFS_BMAPI_REMAP));
> -	ASSERT(!(flags & XFS_BMAPI_CONVERT) || !(flags & XFS_BMAPI_REMAP));
> +	ASSERT(!(flags & XFS_BMAPI_REMAP));
>  
>  	/* zeroing is for currently only for data extents, not metadata */
>  	ASSERT((flags & (XFS_BMAPI_METADATA | XFS_BMAPI_ZERO)) !=
> @@ -4640,13 +4637,8 @@ xfs_bmapi_write(
>  			} else {
>  				need_alloc = true;
>  			}
> -		} else {
> -			/*
> -			 * Make sure we only reflink into a hole.
> -			 */
> -			ASSERT(!(flags & XFS_BMAPI_REMAP));
> -			if (isnullstartblock(bma.got.br_startblock))
> -				wasdelay = true;
> +		} else if (isnullstartblock(bma.got.br_startblock)) {
> +			wasdelay = true;
>  		}
>  
>  		/*
> @@ -4775,6 +4767,89 @@ xfs_bmapi_write(
>  	return error;
>  }
>  
> +static int
> +xfs_bmapi_remap(
> +	struct xfs_trans	*tp,
> +	struct xfs_inode	*ip,
> +	xfs_fileoff_t		bno,
> +	xfs_filblks_t		len,
> +	xfs_fsblock_t		startblock,
> +	struct xfs_defer_ops	*dfops)
> +{
> +	struct xfs_mount	*mp = ip->i_mount;
> +	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> +	struct xfs_btree_cur	*cur = NULL;
> +	xfs_fsblock_t		firstblock = NULLFSBLOCK;
> +	struct xfs_bmbt_irec	got;
> +	xfs_extnum_t		idx;
> +	int			logflags = 0, error;
> +
> +	ASSERT(len > 0);
> +	ASSERT(len <= (xfs_filblks_t)MAXEXTLEN);
> +	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> +	ASSERT(ifp->if_flags & XFS_IFEXTENTS);
> +
> +	if (unlikely(XFS_TEST_ERROR(
> +	    (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
> +	     XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
> +	     mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
> +		XFS_ERROR_REPORT("xfs_bmapi_remap", XFS_ERRLEVEL_LOW, mp);
> +		return -EFSCORRUPTED;
> +	}
> +
> +	if (XFS_FORCED_SHUTDOWN(mp))
> +		return -EIO;
> +
> +	if (xfs_iext_lookup_extent(ip, ifp, bno, &idx, &got)) {
> +		/* make sure we only reflink into a hole. */
> +		ASSERT(got.br_startoff > bno);
> +		ASSERT(got.br_startoff - bno >= len);
> +	}
> +
> +	error = xfs_bmap_remap_alloc(tp, ip, startblock, len);
> +	if (error)
> +		goto error0;
> +
> +	if (ifp->if_flags & XFS_IFBROOT) {
> +		cur = xfs_bmbt_init_cursor(mp, tp, ip, XFS_DATA_FORK);
> +		cur->bc_private.b.firstblock = firstblock;
> +		cur->bc_private.b.dfops = dfops;
> +		cur->bc_private.b.flags = 0;
> +	}
> +
> +	got.br_startoff = bno;
> +	got.br_startblock = startblock;
> +	got.br_blockcount = len;
> +	got.br_state = XFS_EXT_NORM;
> +
> +	error = xfs_bmap_add_extent_hole_real(tp, ip, XFS_DATA_FORK, &idx, &cur,
> +			&got, &firstblock, dfops, &logflags);
> +	if (error)
> +		goto error0;
> +
> +	if (xfs_bmap_wants_extents(ip, XFS_DATA_FORK)) {
> +		int		tmp_logflags = 0;
> +
> +		error = xfs_bmap_btree_to_extents(tp, ip, cur,
> +			&tmp_logflags, XFS_DATA_FORK);
> +		logflags |= tmp_logflags;
> +	}
> +
> +error0:
> +	if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS)
> +		logflags &= ~XFS_ILOG_DEXT;
> +	else if (ip->i_d.di_format != XFS_DINODE_FMT_BTREE)
> +		logflags &= ~XFS_ILOG_DBROOT;
> +
> +	if (logflags)
> +		xfs_trans_log_inode(tp, ip, logflags);
> +	if (cur) {
> +		xfs_btree_del_cursor(cur,
> +			error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);

Double indent here?

xfs_btree_del_cursor(cur,
		error ? ...);

Especially since you do that in one of the subsequent hunks.

> +	}
> +	return error;

I think the code in this function looks ok aside from my earlier
comments.

--D

> +}
> +
>  /*
>   * When a delalloc extent is split (e.g., due to a hole punch), the original
>   * indlen reservation must be shared across the two new extents that are left
> @@ -6493,16 +6568,7 @@ xfs_bmap_finish_one(
>  	xfs_filblks_t			blockcount,
>  	xfs_exntst_t			state)
>  {
> -	struct xfs_bmbt_irec		bmap;
> -	int				nimaps = 1;
> -	xfs_fsblock_t			firstfsb;
> -	int				done;
> -	int				error = 0;
> -
> -	bmap.br_startblock = startblock;
> -	bmap.br_startoff = startoff;
> -	bmap.br_blockcount = blockcount;
> -	bmap.br_state = state;
> +	int				error = 0, done;
>  
>  	trace_xfs_bmap_deferred(tp->t_mountp,
>  			XFS_FSB_TO_AGNO(tp->t_mountp, startblock), type,
> @@ -6519,16 +6585,12 @@ xfs_bmap_finish_one(
>  
>  	switch (type) {
>  	case XFS_BMAP_MAP:
> -		firstfsb = bmap.br_startblock;
> -		error = xfs_bmapi_write(tp, ip, bmap.br_startoff,
> -					bmap.br_blockcount, XFS_BMAPI_REMAP, &firstfsb,
> -					bmap.br_blockcount, &bmap, &nimaps,
> -					dfops);
> +		error = xfs_bmapi_remap(tp, ip, startoff, blockcount,
> +				startblock, dfops);
>  		break;
>  	case XFS_BMAP_UNMAP:
> -		error = xfs_bunmapi(tp, ip, bmap.br_startoff,
> -				bmap.br_blockcount, XFS_BMAPI_REMAP, 1, &firstfsb,
> -				dfops, &done);
> +		error = xfs_bunmapi(tp, ip, startoff, blockcount,
> +				XFS_BMAPI_REMAP, 1, &startblock, dfops, &done);
>  		ASSERT(done);
>  		break;
>  	default:
> -- 
> 2.11.0
> 
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