Partially fixed negative and truncated "Avail" counts in df output.

This fixes PR943.

ffs/ffs_vfsops.c:
ffs_statfs() multiplied by (100 - minfree) as part of calculating the
minfree percentage (complemented in 100%), so with the standard minfree
of 8, it was broken for file systems of size >= 1TB/92 = 11GB.  Use the
standard freespace() macro instead.  This also fixes a rounding bug (the
"Avail" count was sometimes 1 too small).

ffs/* (not fixed):
The freespace() macro multiplies by minfree, so with the standard
minfree of 8, it is broken for file systems of size >= 1TB/8 = 128GB.
This bug is more serious since it affects block allocation.

ffs/ffs_alloc.c (not fixed):
Ordinary users are sometimes allowed to allocate 1 (partial) block
too many so that the "Avail" count goes negative.  E.g., if there is
1 fragment available and the file is fairly large, one more full
block is allocated.

df/df.c:
ufs_df() used/uses essentially the same code as ffs_statfs(), so it
had/has the same bugs.

ufs_df() gratuitously replaced "Avail" counts of < 0 by 0, so it
gave different results for non-mounted file systems in this case.

1 files changed, 2 insertions, 5 deletions

diff --git a/bin/df/df.c b/bin/df/df.c
index 80cbba4..701a9ad 100644
--- a/bin/df/df.c
+++ b/bin/df/df.c
@@ -35,7 +35,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: df.c,v 1.6 1995/03/19 13:28:15 joerg Exp $
+ *	$Id: df.c,v 1.7 1995/05/30 00:06:42 rgrimes Exp $
  */
 
 #ifndef lint
@@ -386,10 +386,7 @@ ufs_df(file, maxwidth)
 	sfsp->f_blocks = sblock.fs_dsize;
 	sfsp->f_bfree = sblock.fs_cstotal.cs_nbfree * sblock.fs_frag +
 		sblock.fs_cstotal.cs_nffree;
-	sfsp->f_bavail = (sblock.fs_dsize * (100 - sblock.fs_minfree) / 100) -
-		(sblock.fs_dsize - sfsp->f_bfree);
-	if (sfsp->f_bavail < 0)
-		sfsp->f_bavail = 0;
+	sfsp->f_bavail = freespace(&sblock, sblock.fs_minfree);
 	sfsp->f_files =  sblock.fs_ncg * sblock.fs_ipg;
 	sfsp->f_ffree = sblock.fs_cstotal.cs_nifree;
 	sfsp->f_fsid.val[0] = 0;