Re: [PATCH 01/14] xfs: new inode extent list lookup helpers

[Brian Foster <bfoster@redhat.com>]

On Mon, Nov 14, 2016 at 06:12:32PM +0100, Christoph Hellwig wrote:
> xfs_iext_lookup_extent looks up a single extent at the passed in offset,
> and returns the extent covering the area, or the one behind it in case
> of a hole, as well as the index of the returned extent in arguments,
> as well as a simple bool as return value that is set to false if no
> extent could be found because the offset is behind EOF.  It is a simpler
> replacement for xfs_bmap_search_extent that leaves looking up the rarely
> needed previous extent to the caller and has a nicer calling convention.
> 
> xfs_iext_get_extent is a helper for iterating over the extent list,
> it takes an extent index as input, and returns the extent at that index
> in it's expanded form in an argument if it exists.  The actual return
> value is a bool whether the index is valid or not.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/libxfs/xfs_inode_fork.c | 46 ++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/libxfs/xfs_inode_fork.h |  6 ++++++
>  2 files changed, 52 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index 5fbe24c..749fbfb 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -2003,3 +2003,49 @@ xfs_ifork_init_cow(
>  	ip->i_cformat = XFS_DINODE_FMT_EXTENTS;
>  	ip->i_cnextents = 0;
>  }
> +
> +/*
> + * Lookup the extent covering bno.
> + *
> + * If there is an extent covering bno return the extent index, and store the
> + * expanded extent structure in *gotp, and the extent indes in *idx.

Typo:							 index

Otherwise looks good:

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

> + * If there is no extent covering bno, but there is an extent after it (e.g.
> + * it lies in a hole) return that extent in *gotp and its index in *idx
> + * instead.
> + * If bno is beyond the last extent return false, and return the index after
> + * the last valid index in *idxp.
> + */
> +bool
> +xfs_iext_lookup_extent(
> +	struct xfs_inode	*ip,
> +	struct xfs_ifork	*ifp,
> +	xfs_fileoff_t		bno,
> +	xfs_extnum_t		*idxp,
> +	struct xfs_bmbt_irec	*gotp)
> +{
> +	struct xfs_bmbt_rec_host *ep;
> +
> +	XFS_STATS_INC(ip->i_mount, xs_look_exlist);
> +
> +	ep = xfs_iext_bno_to_ext(ifp, bno, idxp);
> +	if (!ep)
> +		return false;
> +	xfs_bmbt_get_all(ep, gotp);
> +	return true;
> +}
> +
> +/*
> + * Return true if there is an extent at index idx, and return the expanded
> + * extent structure at idx in that case.  Else return false.
> + */
> +bool
> +xfs_iext_get_extent(
> +	struct xfs_ifork	*ifp,
> +	xfs_extnum_t		idx,
> +	struct xfs_bmbt_irec	*gotp)
> +{
> +	if (idx < 0 || idx >= xfs_iext_count(ifp))
> +		return false;
> +	xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), gotp);
> +	return true;
> +}
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index 8bf112e..7fb8365 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -182,6 +182,12 @@ void		xfs_iext_irec_compact_pages(struct xfs_ifork *);
>  void		xfs_iext_irec_compact_full(struct xfs_ifork *);
>  void		xfs_iext_irec_update_extoffs(struct xfs_ifork *, int, int);
>  
> +bool		xfs_iext_lookup_extent(struct xfs_inode *ip,
> +			struct xfs_ifork *ifp, xfs_fileoff_t bno,
> +			xfs_extnum_t *idxp, struct xfs_bmbt_irec *gotp);
> +bool		xfs_iext_get_extent(struct xfs_ifork *ifp, xfs_extnum_t idx,
> +			struct xfs_bmbt_irec *gotp);
> +
>  extern struct kmem_zone	*xfs_ifork_zone;
>  
>  extern void xfs_ifork_init_cow(struct xfs_inode *ip);
> -- 
> 2.1.4
> 
> --
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