xfs: cleanup xfs_reflink_find_cow_mapping

Use xfs_iext_lookup_extent to look up the extent, drop a useless check,
drop a unneeded return value and clean up the general style a little bit.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_aops.c

@@ -777,7 +777,7 @@ xfs_map_cow(
 {
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct xfs_bmbt_irec	imap;
-	bool			is_cow = false, need_alloc = false;
+	bool			is_cow = false;
 	int			error;
 
 	/*
@@ -795,7 +795,7 @@ xfs_map_cow(
 	 * Else we need to check if there is a COW mapping at this offset.
 	 */
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
-	is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap, &need_alloc);
+	is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap);
 	xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
 	if (!is_cow)
@@ -805,7 +805,7 @@ xfs_map_cow(
 	 * And if the COW mapping has a delayed extent here we need to
 	 * allocate real space for it now.
 	 */
-	if (need_alloc) {
+	if (isnullstartblock(imap.br_startblock)) {
 		error = xfs_iomap_write_allocate(ip, XFS_COW_FORK, offset,
 				&imap);
 		if (error)
@@ -1312,7 +1312,6 @@ __xfs_get_blocks(
 	ssize_t			size;
 	int			new = 0;
 	bool			is_cow = false;
-	bool			need_alloc = false;
 
 	BUG_ON(create && !direct);
 
@@ -1338,9 +1337,11 @@ __xfs_get_blocks(
 	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + size);
 	offset_fsb = XFS_B_TO_FSBT(mp, offset);
 
-	if (create && direct && xfs_is_reflink_inode(ip))
-		is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap,
-					&need_alloc);
+	if (create && direct && xfs_is_reflink_inode(ip)) {
+		is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap);
+		ASSERT(!is_cow || !isnullstartblock(imap.br_startblock));
+	}
+
 	if (!is_cow) {
 		error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
 					&imap, &nimaps, XFS_BMAPI_ENTIRE);
@@ -1357,7 +1358,6 @@ __xfs_get_blocks(
 			xfs_reflink_trim_irec_to_next_cow(ip, offset_fsb,
 					&imap);
 	}
-	ASSERT(!need_alloc);
 	if (error)
 		goto out_unlock;
 

fs/xfs/xfs_reflink.c

@@ -420,44 +420,31 @@ xfs_reflink_allocate_cow_range(
 }
 
 /*
- * Find the CoW reservation (and whether or not it needs block allocation)
- * for a given byte offset of a file.
+ * Find the CoW reservation for a given byte offset of a file.
  */
 bool
 xfs_reflink_find_cow_mapping(
 	struct xfs_inode		*ip,
 	xfs_off_t			offset,
-	struct xfs_bmbt_irec		*imap,
-	bool				*need_alloc)
+	struct xfs_bmbt_irec		*imap)
 {
-	struct xfs_bmbt_irec		irec;
-	struct xfs_ifork		*ifp;
-	struct xfs_bmbt_rec_host	*gotp;
-	xfs_fileoff_t			bno;
+	struct xfs_ifork		*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+	xfs_fileoff_t			offset_fsb;
+	struct xfs_bmbt_irec		got;
 	xfs_extnum_t			idx;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
 	ASSERT(xfs_is_reflink_inode(ip));
 
-	/* Find the extent in the CoW fork. */
-	ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
-	bno = XFS_B_TO_FSBT(ip->i_mount, offset);
-	gotp = xfs_iext_bno_to_ext(ifp, bno, &idx);
-	if (!gotp)
+	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+	if (!xfs_iext_lookup_extent(ip, ifp, offset_fsb, &idx, &got))
 		return false;
-
-	xfs_bmbt_get_all(gotp, &irec);
-	if (bno >= irec.br_startoff + irec.br_blockcount ||
-	    bno < irec.br_startoff)
+	if (got.br_startoff > offset_fsb)
 		return false;
 
 	trace_xfs_reflink_find_cow_mapping(ip, offset, 1, XFS_IO_OVERWRITE,
-			&irec);
-
-	/* If it's still delalloc, we must allocate later. */
-	*imap = irec;
-	*need_alloc = !!(isnullstartblock(irec.br_startblock));
-
+			&got);
+	*imap = got;
 	return true;
 }
 

fs/xfs/xfs_reflink.h

@@ -31,7 +31,7 @@ extern int xfs_reflink_reserve_cow(struct xfs_inode *ip,
 extern int xfs_reflink_allocate_cow_range(struct xfs_inode *ip,
 		xfs_off_t offset, xfs_off_t count);
 extern bool xfs_reflink_find_cow_mapping(struct xfs_inode *ip, xfs_off_t offset,
-		struct xfs_bmbt_irec *imap, bool *need_alloc);
+		struct xfs_bmbt_irec *imap);
 extern int xfs_reflink_trim_irec_to_next_cow(struct xfs_inode *ip,
 		xfs_fileoff_t offset_fsb, struct xfs_bmbt_irec *imap);