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, 79 insertions, 8 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 113fd42ec36d..d454161793e2 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -151,12 +151,13 @@ void		xfs_init_local_fork(struct xfs_inode *, int, const void *, int);
 struct xfs_bmbt_rec_host *
 		xfs_iext_get_ext(struct xfs_ifork *, xfs_extnum_t);
 xfs_extnum_t	xfs_iext_count(struct xfs_ifork *);
-void		xfs_iext_insert(struct xfs_inode *, xfs_extnum_t, xfs_extnum_t,
-				struct xfs_bmbt_irec *, int);
+void		xfs_iext_insert(struct xfs_inode *, struct xfs_iext_cursor *cur,
+			xfs_extnum_t, struct xfs_bmbt_irec *, int);
 void		xfs_iext_add(struct xfs_ifork *, xfs_extnum_t, int);
 void		xfs_iext_add_indirect_multi(struct xfs_ifork *, int,
 					    xfs_extnum_t, int);
-void		xfs_iext_remove(struct xfs_inode *, xfs_extnum_t, int, int);
+void		xfs_iext_remove(struct xfs_inode *, struct xfs_iext_cursor *,
+			int, int);
 void		xfs_iext_remove_inline(struct xfs_ifork *, xfs_extnum_t, int);
 void		xfs_iext_remove_direct(struct xfs_ifork *, xfs_extnum_t, int);
 void		xfs_iext_remove_indirect(struct xfs_ifork *, xfs_extnum_t, int);
@@ -182,15 +183,85 @@ 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);
+			struct xfs_iext_cursor *cur,
+			struct xfs_bmbt_irec *gotp);
 bool		xfs_iext_lookup_extent_before(struct xfs_inode *ip,
 			struct xfs_ifork *ifp, xfs_fileoff_t *end,
-			xfs_extnum_t *idxp, struct xfs_bmbt_irec *gotp);
-
-bool		xfs_iext_get_extent(struct xfs_ifork *ifp, xfs_extnum_t idx,
+			struct xfs_iext_cursor *cur,
+			struct xfs_bmbt_irec *gotp);
+bool		xfs_iext_get_extent(struct xfs_ifork *ifp,
+			struct xfs_iext_cursor *cur,
 			struct xfs_bmbt_irec *gotp);
 void		xfs_iext_update_extent(struct xfs_inode *ip, int state,
-			xfs_extnum_t idx, struct xfs_bmbt_irec *gotp);
+			struct xfs_iext_cursor *cur,
+			struct xfs_bmbt_irec *gotp);
+
+static inline void xfs_iext_first(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur)
+{
+	cur->idx = 0;
+}
+
+static inline void xfs_iext_last(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur)
+{
+	cur->idx = xfs_iext_count(ifp) - 1;
+}
+
+static inline void xfs_iext_next(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur)
+{
+	cur->idx++;
+}
+
+static inline void xfs_iext_prev(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur)
+{
+	cur->idx--;
+}
+
+static inline bool xfs_iext_next_extent(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur, struct xfs_bmbt_irec *gotp)
+{
+	xfs_iext_next(ifp, cur);
+	return xfs_iext_get_extent(ifp, cur, gotp);
+}
+
+static inline bool xfs_iext_prev_extent(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur, struct xfs_bmbt_irec *gotp)
+{
+	xfs_iext_prev(ifp, cur);
+	return xfs_iext_get_extent(ifp, cur, gotp);
+}
+
+/*
+ * Return the extent after cur in gotp without updating the cursor.
+ */
+static inline bool xfs_iext_peek_next_extent(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur, struct xfs_bmbt_irec *gotp)
+{
+	struct xfs_iext_cursor ncur = *cur;
+
+	xfs_iext_next(ifp, &ncur);
+	return xfs_iext_get_extent(ifp, &ncur, gotp);
+}
+
+/*
+ * Return the extent before cur in gotp without updating the cursor.
+ */
+static inline bool xfs_iext_peek_prev_extent(struct xfs_ifork *ifp,
+		struct xfs_iext_cursor *cur, struct xfs_bmbt_irec *gotp)
+{
+	struct xfs_iext_cursor ncur = *cur;
+
+	xfs_iext_prev(ifp, &ncur);
+	return xfs_iext_get_extent(ifp, &ncur, gotp);
+}
+
+#define for_each_xfs_iext(ifp, ext, got)		\
+	for (xfs_iext_first((ifp), (ext));		\
+	     xfs_iext_get_extent((ifp), (ext), (got));	\
+	     xfs_iext_next((ifp), (ext)))
 
 extern struct kmem_zone	*xfs_ifork_zone;