xfs: simplify xfs_reflink_convert_cow

Instead of looking up extents to convert and calling xfs_bmapi_write on
each of them just let xfs_bmapi_write handle the full range.  To make
this robust add a new XFS_BMAPI_CONVERT_ONLY that only converts ranges
and never allocates blocks.

[darrick: shorten the stringified CONVERT_ONLY trace flag]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 11 insertions, 18 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index cf976ed..cc041a2 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -353,29 +353,22 @@ xfs_reflink_convert_cow(
 	xfs_off_t		offset,
 	xfs_off_t		count)
 {
-	struct xfs_bmbt_irec	got;
-	struct xfs_defer_ops	dfops;
 	struct xfs_mount	*mp = ip->i_mount;
-	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
 	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
 	xfs_fileoff_t		end_fsb = XFS_B_TO_FSB(mp, offset + count);
-	struct xfs_iext_cursor	icur;
-	bool			found;
-	int			error = 0;
-
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	xfs_filblks_t		count_fsb = end_fsb - offset_fsb;
+	struct xfs_bmbt_irec	imap;
+	struct xfs_defer_ops	dfops;
+	xfs_fsblock_t		first_block = NULLFSBLOCK;
+	int			nimaps = 1, error = 0;
 
-	/* Convert all the extents to real from unwritten. */
-	for (found = xfs_iext_lookup_extent(ip, ifp, offset_fsb, &icur, &got);
-	     found && got.br_startoff < end_fsb;
-	     found = xfs_iext_next_extent(ifp, &icur, &got)) {
-		error = xfs_reflink_convert_cow_extent(ip, &got, offset_fsb,
-				end_fsb - offset_fsb, &dfops);
-		if (error)
-			break;
-	}
+	ASSERT(count != 0);
 
-	/* Finish up. */
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	error = xfs_bmapi_write(NULL, ip, offset_fsb, count_fsb,
+			XFS_BMAPI_COWFORK | XFS_BMAPI_CONVERT |
+			XFS_BMAPI_CONVERT_ONLY, &first_block, 0, &imap, &nimaps,
+			&dfops);
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;
 }