[PATCH 30/37] libxfs: work around do_div() not handling 32 bit numerators

Dave Chinner
2013-11-06T01:07:48Z

The libxfs dquot buffer code uses do_div() with a 32 bit numerator.
This gives incorrect results as do_div() passes the numerator by
reference as a pointer to a 64 bit value. Hence it does the division
using 32 bits of garbage gives the wrong result.

As per Christoph's suggestion, we can kill the usage of do_div()
here completely and just do the division directly, both in userspace
and kernel space.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
libxfs/xfs_dquot_buf.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/libxfs/xfs_dquot_buf.c b/libxfs/xfs_dquot_buf.c
index 620d9d3..6bbb0ff 100644
--- a/libxfs/xfs_dquot_buf.c
+++ b/libxfs/xfs_dquot_buf.c
@@ -23,13 +23,8 @@ xfs_calc_dquots_per_chunk(
struct xfs_mount *mp,
unsigned int nbblks) /* basic block units */
{
- unsigned int ndquots;
-
ASSERT(nbblks > 0);
- ndquots = BBTOB(nbblks);
- do_div(ndquots, sizeof(xfs_dqblk_t));
-
- return ndquots;
+ return BBTOB(nbblks) / sizeof(xfs_dqblk_t);
}

/*