Re: [PATCH 11/24] xfs: map an inode's offset to an exact physical block

Dave Chinner
2015-07-30T01:05:43Z

On Wed, Jul 29, 2015 at 03:34:09PM -0700, Darrick J. Wong wrote:
> Teach the bmap routine to know how to map a range of file blocks to a
> specific range of physical blocks, instead of simply allocating fresh
> blocks. This enables reflink to map a file to blocks that are already
> in use.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> fs/xfs/libxfs/xfs_bmap.c | 21 +++++++++++++++++++++
> fs/xfs/libxfs/xfs_bmap.h | 3 +++
> 2 files changed, 24 insertions(+)
>
>
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index dfdd9e6..1297b94 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3897,6 +3897,15 @@ STATIC int
> xfs_bmap_alloc(
> struct xfs_bmalloca *ap) /* bmap alloc argument struct */
> {
> + if (ap->flags & XFS_BMAPI_EXACT) {
> + trace_xfs_reflink_relink_blocks(ap->ip, *ap->firstblock,
> + ap->length);
> + ap->blkno = *ap->firstblock;
> + ap->ip->i_d.di_nblocks += ap->length;
> + xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
> + return 0;
> + }

XFS_BMAPI_EXACT is confusing to me - "exact" already means something
in the xfs_bmapi API w.r.t. the XFS_BMAPI_ENTIRE flag. That is, if
XFS_BMAPI_ENTIRE is not set, we want the map returned to span only
the /exact range requested/. If XFS_BMAPI_ENTIRE is set, we want the
entire extent that overlaps the range requested...

So I think this might be better named to match it's intended
function. e.g. remap, reuse, ref_only, etc.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com