xfs: create helpers to convert rt block numbers to rt extent numbers

Create helpers to do unit conversions of rt block numbers to rt extent
numbers.  There are three variations -- one to compute the rt extent
number from an rt block number; one to compute the offset of an rt block
within an rt extent; and one to extract both.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_bmap.c

@@ -5276,7 +5276,6 @@ __xfs_bunmapi(
 	int			tmp_logflags;	/* partial logging flags */
 	int			wasdel;		/* was a delayed alloc extent */
 	int			whichfork;	/* data or attribute fork */
-	xfs_fsblock_t		sum;
 	xfs_filblks_t		len = *rlen;	/* length to unmap in file */
 	xfs_fileoff_t		end;
 	struct xfs_iext_cursor	icur;
@@ -5371,8 +5370,8 @@ __xfs_bunmapi(
 		if (!isrt)
 			goto delete;
 
-		sum = del.br_startblock + del.br_blockcount;
-		div_u64_rem(sum, mp->m_sb.sb_rextsize, &mod);
+		mod = xfs_rtb_to_rtxoff(mp,
+				del.br_startblock + del.br_blockcount);
 		if (mod) {
 			/*
 			 * Realtime extent not lined up at the end.
@@ -5419,7 +5418,8 @@ __xfs_bunmapi(
 				goto error0;
 			goto nodelete;
 		}
-		div_u64_rem(del.br_startblock, mp->m_sb.sb_rextsize, &mod);
+
+		mod = xfs_rtb_to_rtxoff(mp, del.br_startblock);
 		if (mod) {
 			xfs_extlen_t off = mp->m_sb.sb_rextsize - mod;
 

fs/xfs/libxfs/xfs_rtbitmap.c

@@ -1024,13 +1024,13 @@ xfs_rtfree_blocks(
 
 	ASSERT(rtlen <= XFS_MAX_BMBT_EXTLEN);
 
-	len = div_u64_rem(rtlen, mp->m_sb.sb_rextsize, &mod);
+	len = xfs_rtb_to_rtxrem(mp, rtlen, &mod);
 	if (mod) {
 		ASSERT(mod == 0);
 		return -EIO;
 	}
 
-	start = div_u64_rem(rtbno, mp->m_sb.sb_rextsize, &mod);
+	start = xfs_rtb_to_rtxrem(mp, rtbno, &mod);
 	if (mod) {
 		ASSERT(mod == 0);
 		return -EIO;

fs/xfs/libxfs/xfs_rtbitmap.h

@@ -39,6 +39,37 @@ xfs_extlen_to_rtxlen(
 	return len / mp->m_sb.sb_rextsize;
 }
 
+/* Convert an rt block number into an rt extent number. */
+static inline xfs_rtxnum_t
+xfs_rtb_to_rtx(
+	struct xfs_mount	*mp,
+	xfs_rtblock_t		rtbno)
+{
+	return div_u64(rtbno, mp->m_sb.sb_rextsize);
+}
+
+/* Return the offset of an rt block number within an rt extent. */
+static inline xfs_extlen_t
+xfs_rtb_to_rtxoff(
+	struct xfs_mount	*mp,
+	xfs_rtblock_t		rtbno)
+{
+	return do_div(rtbno, mp->m_sb.sb_rextsize);
+}
+
+/*
+ * Crack an rt block number into an rt extent number and an offset within that
+ * rt extent.  Returns the rt extent number directly and the offset in @off.
+ */
+static inline xfs_rtxnum_t
+xfs_rtb_to_rtxrem(
+	struct xfs_mount	*mp,
+	xfs_rtblock_t		rtbno,
+	xfs_extlen_t		*off)
+{
+	return div_u64_rem(rtbno, mp->m_sb.sb_rextsize, off);
+}
+
 /*
  * Functions for walking free space rtextents in the realtime bitmap.
  */