On Sat, Oct 15, 2016 at 10:52:27AM +0200, Christoph Hellwig wrote:
> From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
>
> This helpers allows to trim an extent to a subset of it's original range
> while making sure the block numbers in it remain valid,
>
> In the future xfs_trim_extent and xfs_bmapi_trim_map should probably be
> merged in some form.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> [hch: split from a previous patch from Darrick, moved around and added
> support for "raw" delayed extents"]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 33 +++++++++++++++++++++++++++++++++
> fs/xfs/libxfs/xfs_bmap.h | 2 ++
> 2 files changed, 35 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index c27344c..016dacc 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3999,6 +3999,39 @@ xfs_bmap_alloc(
> return xfs_bmap_btalloc(ap);
> }
>
> +/* Trim extent to fit a logical block range. */
> +void
> +xfs_trim_extent(
> + struct xfs_bmbt_irec *irec,
> + xfs_fileoff_t bno,
> + xfs_filblks_t len)
> +{
> + xfs_fileoff_t distance;
> + xfs_fileoff_t end = bno + len;
> +
> + if (irec->br_startoff + irec->br_blockcount <= bno ||
> + irec->br_startoff >= end) {
> + irec->br_blockcount = 0;
> + return;
> + }
> +
> + if (irec->br_startoff < bno) {
> + distance = bno - irec->br_startoff;
> + if (isnullstartblock(irec->br_startblock))
> + irec->br_startblock = DELAYSTARTBLOCK;
> + if (irec->br_startblock != DELAYSTARTBLOCK &&
> + irec->br_startblock != HOLESTARTBLOCK)
> + irec->br_startblock += distance;
> + irec->br_startoff += distance;
> + irec->br_blockcount -= distance;
> + }
> +
> + if (end < irec->br_startoff + irec->br_blockcount) {
> + distance = irec->br_startoff + irec->br_blockcount - end;
> + irec->br_blockcount -= distance;
> + }
> +}
> +
> /*
> * Trim the returned map to the required bounds
> */
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index f97db71..eb86af0 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -190,6 +190,8 @@ void xfs_bmap_trace_exlist(struct xfs_inode *ip, xfs_extnum_t cnt,
> #define XFS_BMAP_TRACE_EXLIST(ip,c,w)
> #endif
>
> +void xfs_trim_extent(struct xfs_bmbt_irec *irec, xfs_fileoff_t bno,
> + xfs_filblks_t len);
> int xfs_bmap_add_attrfork(struct xfs_inode *ip, int size, int rsvd);
> void xfs_bmap_local_to_extents_empty(struct xfs_inode *ip, int whichfork);
> void xfs_bmap_add_free(struct xfs_mount *mp, struct xfs_defer_ops *dfops,
> --
> 2.1.4
>
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