[PATCH 2/3] xfs: fix 32-bit truncation in xfs_compute_rextslog

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

It's quite reasonable that some customer somewhere will want to
configure a realtime volume with more than 2^32 extents.  If they try to
do this, the highbit32() call will truncate the upper bits of the
xfs_rtbxlen_t and produce the wrong value for rextslog.  This in turn
causes the rsumlevels to be wrong, which results in a realtime summary
file that is the wrong length.  Fix that.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_rtbitmap.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 1c9fed76a356..0626909a2481 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -1132,14 +1132,14 @@ xfs_rtbitmap_blockcount(
 
 /*
  * Compute the maximum level number of the realtime summary file, as defined by
- * mkfs.  The use of highbit32 on a 64-bit quantity is a historic artifact that
- * prohibits correct use of rt volumes with more than 2^32 extents.
+ * mkfs.  The historic use of highbit32 on a 64-bit quantity prohibited correct
+ * use of rt volumes with more than 2^32 extents.
  */
 uint8_t
 xfs_compute_rextslog(
 	xfs_rtbxlen_t		rtextents)
 {
-	return rtextents ? xfs_highbit32(rtextents) : 0;
+	return rtextents ? xfs_highbit64(rtextents) : 0;
 }
 
 /*