[PATCH 6.1 18/29] xfs: fix 32-bit truncation in xfs_compute_rextslog

From: "Darrick J. Wong" <[email protected]>

[ Upstream commit cf8f0e6c1429be7652869059ea44696b72d5b726 ]

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 <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Leah Rumancik <[email protected]>
Acked-by: "Darrick J. Wong" <[email protected]>
---
 fs/xfs/libxfs/xfs_rtbitmap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 37b425ea3fed..8db1243beacc 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -1131,15 +1131,17 @@ xfs_rtalloc_extent_is_free(
 	return 0;
 }
 
 /*
  * 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;
+	if (!rtextents)
+		return 0;
+	return xfs_highbit64(rtextents);
 }
 
-- 
2.49.0.rc1.451.g8f38331e32-goog