Re: [PATCH 10/18] xfs: iterate over extents in xfs_iextents_copy

[Brian Foster <bfoster@redhat.com>]

On Tue, Oct 31, 2017 at 04:22:22PM +0200, Christoph Hellwig wrote:
> This actually makes the function very slightly less efficient for now as we
> detour through the expanded irect format between the in-core extent format
> and the on-disk one instead of just endian swapping them.  But with the
> incore extent btree the in-core one will use a different format and the
> representation will be entirely hidden.  It also happens to make the
> function a whole more readable.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

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

>  fs/xfs/libxfs/xfs_inode_fork.c | 53 +++++++++++-------------------------------
>  1 file changed, 13 insertions(+), 40 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index abe601b48c9c..7dd77b497fc2 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -725,9 +725,6 @@ xfs_iext_count(struct xfs_ifork *ifp)
>  /*
>   * Convert in-core extents to on-disk form
>   *
> - * For either the data or attr fork in extent format, we need to endian convert
> - * the in-core extent as we place them into the on-disk inode.
> - *
>   * In the case of the data fork, the in-core and on-disk fork sizes can be
>   * different due to delayed allocation extents. We only copy on-disk extents
>   * here, so callers must always use the physical fork size to determine the
> @@ -736,55 +733,31 @@ xfs_iext_count(struct xfs_ifork *ifp)
>   */
>  int
>  xfs_iextents_copy(
> -	xfs_inode_t		*ip,
> -	xfs_bmbt_rec_t		*dp,
> +	struct xfs_inode	*ip,
> +	struct xfs_bmbt_rec	*dp,
>  	int			whichfork)
>  {
>  	int			state = xfs_bmap_fork_to_state(whichfork);
> -	int			copied;
> -	int			i;
> -	xfs_ifork_t		*ifp;
> -	int			nrecs;
> -	xfs_fsblock_t		start_block;
> +	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, whichfork);
> +	struct xfs_bmbt_irec	rec;
> +	int			copied = 0, i = 0;
>  
> -	ifp = XFS_IFORK_PTR(ip, whichfork);
> -	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
> +	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
>  	ASSERT(ifp->if_bytes > 0);
>  
> -	nrecs = xfs_iext_count(ifp);
> -	ASSERT(nrecs > 0);
> -
> -	/*
> -	 * There are some delayed allocation extents in the
> -	 * inode, so copy the extents one at a time and skip
> -	 * the delayed ones.  There must be at least one
> -	 * non-delayed extent.
> -	 */
> -	copied = 0;
> -	for (i = 0; i < nrecs; i++) {
> -		xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
> -
> -		start_block = xfs_bmbt_get_startblock(ep);
> -		if (isnullstartblock(start_block)) {
> -			/*
> -			 * It's a delayed allocation extent, so skip it.
> -			 */
> +	while (xfs_iext_get_extent(ifp, i++, &rec)) {
> +		if (isnullstartblock(rec.br_startblock))
>  			continue;
> -		}
> -
> +		xfs_bmbt_disk_set_all(dp, &rec);
>  		trace_xfs_write_extent(ip, i, state, _RET_IP_);
> -
> -		/* Translate to on disk format */
> -		put_unaligned_be64(ep->l0, &dp->l0);
> -		put_unaligned_be64(ep->l1, &dp->l1);
>  		ASSERT(xfs_bmbt_validate_extent(ip->i_mount, whichfork, dp));
> -
> +		copied += sizeof(struct xfs_bmbt_rec);
>  		dp++;
> -		copied++;
>  	}
> -	ASSERT(copied != 0);
>  
> -	return (copied * (uint)sizeof(xfs_bmbt_rec_t));
> +	ASSERT(copied > 0);
> +	ASSERT(copied <= ifp->if_bytes);
> +	return copied;
>  }
>  
>  /*
> -- 
> 2.14.2
> 
> --
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