[PATCH 6.6 09/24] xfs: fix 32-bit truncation in xfs_compute_rextslog

Catherine Hoang
2024-03-27T00:13:05Z

commit cf8f0e6c1429be7652869059ea44696b72d5b726 upstream.

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
---
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
@@ -1133,13 +1133,15 @@ xfs_rtalloc_extent_is_free(

/*
* 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);
}

--
2.39.3