xfs: introduce the xfs_iext_cursor abstraction

Add a new xfs_iext_cursor structure to hide the direct extent map
index manipulations. In addition to the existing lookup/get/insert/
remove and update routines new primitives to get the first and last
extent cursor, as well as moving up and down by one extent are
provided.  Also new are convenience to increment/decrement the
cursor and retreive the new extent, as well as to peek into the
previous/next extent without updating the cursor and last but not
least a macro to iterate over all extents in a fork.

[darrick: rename for_each_iext to for_each_xfs_iext]

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

1 files changed, 41 insertions, 34 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 7dd77b497fc2..61d02b708a6b 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -343,6 +343,7 @@ xfs_iformat_extents(
 	int			state = xfs_bmap_fork_to_state(whichfork);
 	int			nex = XFS_DFORK_NEXTENTS(dip, whichfork);
 	int			size = nex * sizeof(xfs_bmbt_rec_t);
+	struct xfs_iext_cursor	icur;
 	struct xfs_bmbt_rec	*dp;
 	int			i;
 
@@ -369,16 +370,21 @@ xfs_iformat_extents(
 	ifp->if_bytes = size;
 	if (size) {
 		dp = (xfs_bmbt_rec_t *) XFS_DFORK_PTR(dip, whichfork);
+
+		xfs_iext_first(ifp, &icur);
 		for (i = 0; i < nex; i++, dp++) {
 			xfs_bmbt_rec_host_t *ep = xfs_iext_get_ext(ifp, i);
+
 			if (!xfs_bmbt_validate_extent(mp, whichfork, dp)) {
 				XFS_ERROR_REPORT("xfs_iformat_extents(2)",
 						 XFS_ERRLEVEL_LOW, mp);
 				return -EFSCORRUPTED;
 			}
+
 			ep->l0 = get_unaligned_be64(&dp->l0);
 			ep->l1 = get_unaligned_be64(&dp->l1);
-			trace_xfs_read_extent(ip, i, state, _THIS_IP_);
+			trace_xfs_read_extent(ip, &icur, state, _THIS_IP_);
+			xfs_iext_next(ifp, &icur);
 		}
 	}
 	ifp->if_flags |= XFS_IFEXTENTS;
@@ -739,17 +745,18 @@ xfs_iextents_copy(
 {
 	int			state = xfs_bmap_fork_to_state(whichfork);
 	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, whichfork);
+	struct xfs_iext_cursor	icur;
 	struct xfs_bmbt_irec	rec;
-	int			copied = 0, i = 0;
+	int			copied = 0;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
 	ASSERT(ifp->if_bytes > 0);
 
-	while (xfs_iext_get_extent(ifp, i++, &rec)) {
+	for_each_xfs_iext(ifp, &icur, &rec) {
 		if (isnullstartblock(rec.br_startblock))
 			continue;
 		xfs_bmbt_disk_set_all(dp, &rec);
-		trace_xfs_write_extent(ip, i, state, _RET_IP_);
+		trace_xfs_write_extent(ip, &icur, state, _RET_IP_);
 		ASSERT(xfs_bmbt_validate_extent(ip->i_mount, whichfork, dp));
 		copied += sizeof(struct xfs_bmbt_rec);
 		dp++;
@@ -894,7 +901,7 @@ xfs_iext_state_to_fork(
 void
 xfs_iext_insert(
 	xfs_inode_t	*ip,		/* incore inode pointer */
-	xfs_extnum_t	idx,		/* starting index of new items */
+	struct xfs_iext_cursor *cur,
 	xfs_extnum_t	count,		/* number of inserted items */
 	xfs_bmbt_irec_t	*new,		/* items to insert */
 	int		state)		/* type of extent conversion */
@@ -902,12 +909,12 @@ xfs_iext_insert(
 	xfs_ifork_t	*ifp = xfs_iext_state_to_fork(ip, state);
 	xfs_extnum_t	i;		/* extent record index */
 
-	trace_xfs_iext_insert(ip, idx, new, state, _RET_IP_);
+	trace_xfs_iext_insert(ip, cur->idx, new, state, _RET_IP_);
 
 	ASSERT(ifp->if_flags & XFS_IFEXTENTS);
-	xfs_iext_add(ifp, idx, count);
-	for (i = idx; i < idx + count; i++, new++)
-		xfs_bmbt_set_all(xfs_iext_get_ext(ifp, i), new);
+	xfs_iext_add(ifp, cur->idx, count);
+	for (i = 0; i < count; i++, new++)
+		xfs_bmbt_set_all(xfs_iext_get_ext(ifp, cur->idx + i), new);
 }
 
 /*
@@ -1145,7 +1152,7 @@ xfs_iext_add_indirect_multi(
 void
 xfs_iext_remove(
 	xfs_inode_t	*ip,		/* incore inode pointer */
-	xfs_extnum_t	idx,		/* index to begin removing exts */
+	struct xfs_iext_cursor *cur,
 	int		ext_diff,	/* number of extents to remove */
 	int		state)		/* type of extent conversion */
 {
@@ -1153,7 +1160,7 @@ xfs_iext_remove(
 	xfs_extnum_t	nextents;	/* number of extents in file */
 	int		new_size;	/* size of extents after removal */
 
-	trace_xfs_iext_remove(ip, idx, state, _RET_IP_);
+	trace_xfs_iext_remove(ip, cur, state, _RET_IP_);
 
 	ASSERT(ext_diff > 0);
 	nextents = xfs_iext_count(ifp);
@@ -1162,11 +1169,11 @@ xfs_iext_remove(
 	if (new_size == 0) {
 		xfs_iext_destroy(ifp);
 	} else if (ifp->if_flags & XFS_IFEXTIREC) {
-		xfs_iext_remove_indirect(ifp, idx, ext_diff);
+		xfs_iext_remove_indirect(ifp, cur->idx, ext_diff);
 	} else if (ifp->if_real_bytes) {
-		xfs_iext_remove_direct(ifp, idx, ext_diff);
+		xfs_iext_remove_direct(ifp, cur->idx, ext_diff);
 	} else {
-		xfs_iext_remove_inline(ifp, idx, ext_diff);
+		xfs_iext_remove_inline(ifp, cur->idx, ext_diff);
 	}
 	ifp->if_bytes = new_size;
 }
@@ -1913,26 +1920,26 @@ xfs_ifork_init_cow(
  * 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 index in *idx.
+ * expanded extent structure in *gotp, and the extent cursor in *cur.
  * 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
+ * it lies in a hole) return that extent in *gotp and its cursor in *cur
  * instead.
- * If bno is beyond the last extent return false, and return the index after
- * the last valid index in *idxp.
+ * If bno is beyond the last extent return false, and return an invalid
+ * cursor value.
  */
 bool
 xfs_iext_lookup_extent(
 	struct xfs_inode	*ip,
 	struct xfs_ifork	*ifp,
 	xfs_fileoff_t		bno,
-	xfs_extnum_t		*idxp,
+	struct xfs_iext_cursor	*cur,
 	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);
+	ep = xfs_iext_bno_to_ext(ifp, bno, &cur->idx);
 	if (!ep)
 		return false;
 	xfs_bmbt_get_all(ep, gotp);
@@ -1948,31 +1955,31 @@ xfs_iext_lookup_extent_before(
 	struct xfs_inode	*ip,
 	struct xfs_ifork	*ifp,
 	xfs_fileoff_t		*end,
-	xfs_extnum_t		*idxp,
+	struct xfs_iext_cursor	*cur,
 	struct xfs_bmbt_irec	*gotp)
 {
-	if (xfs_iext_lookup_extent(ip, ifp, *end - 1, idxp, gotp) &&
+	if (xfs_iext_lookup_extent(ip, ifp, *end - 1, cur, gotp) &&
 	    gotp->br_startoff <= *end - 1)
 		return true;
-	if (!xfs_iext_get_extent(ifp, --*idxp, gotp))
+	if (!xfs_iext_prev_extent(ifp, cur, gotp))
 		return false;
 	*end = gotp->br_startoff + gotp->br_blockcount;
 	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.
+ * Return true if the cursor points at an extent and return the extent structure
+ * in gotp.  Else return false.
  */
 bool
 xfs_iext_get_extent(
 	struct xfs_ifork	*ifp,
-	xfs_extnum_t		idx,
+	struct xfs_iext_cursor	*cur,
 	struct xfs_bmbt_irec	*gotp)
 {
-	if (idx < 0 || idx >= xfs_iext_count(ifp))
+	if (cur->idx < 0 || cur->idx >= xfs_iext_count(ifp))
 		return false;
-	xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), gotp);
+	xfs_bmbt_get_all(xfs_iext_get_ext(ifp, cur->idx), gotp);
 	return true;
 }
 
@@ -1980,15 +1987,15 @@ void
 xfs_iext_update_extent(
 	struct xfs_inode	*ip,
 	int			state,
-	xfs_extnum_t		idx,
+	struct xfs_iext_cursor	*cur,
 	struct xfs_bmbt_irec	*gotp)
 {
 	struct xfs_ifork	*ifp = xfs_iext_state_to_fork(ip, state);
 
-	ASSERT(idx >= 0);
-	ASSERT(idx < xfs_iext_count(ifp));
+	ASSERT(cur->idx >= 0);
+	ASSERT(cur->idx < xfs_iext_count(ifp));
 
-	trace_xfs_bmap_pre_update(ip, idx, state, _RET_IP_);
-	xfs_bmbt_set_all(xfs_iext_get_ext(ifp, idx), gotp);
-	trace_xfs_bmap_post_update(ip, idx, state, _RET_IP_);
+	trace_xfs_bmap_pre_update(ip, cur, state, _RET_IP_);
+	xfs_bmbt_set_all(xfs_iext_get_ext(ifp, cur->idx), gotp);
+	trace_xfs_bmap_post_update(ip, cur, state, _RET_IP_);
 }