[PATCH 002 of 5] md: Stop using csum_partial for checksum calculation in md.

NeilBrown
2007-05-08T04:30:04Z

If CONFIG_NET is not selected, csum_partial is not exported, so
md.ko cannot use it.
We shouldn't really be using csum_partial anyway as it is an
internal-to-networking interface.

So replace it with C code to do the same thing. Speed is not
crucial here, so something simple and correct is best.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/md.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c 2007-05-07 14:33:31.000000000 +1000
+++ ./drivers/md/md.c 2007-05-07 14:57:41.000000000 +1000
@@ -590,14 +590,41 @@ abort:
return ret;
}

+
+static u32 md_csum_fold(u32 csum)
+{
+ csum = (csum & 0xffff) + (csum >> 16);
+ return (csum & 0xffff) + (csum >> 16);
+}
+
static unsigned int calc_sb_csum(mdp_super_t * sb)
{
+ u64 newcsum = 0;
+ u32 *sb32 = (u32*)sb;
+ int i;
unsigned int disk_csum, csum;

disk_csum = sb->sb_csum;
sb->sb_csum = 0;
- csum = csum_partial((void *)sb, MD_SB_BYTES, 0);
+
+ for (i = 0; i < MD_SB_BYTES/4 ; i++)
+ newcsum += sb32[i];
+ csum = (newcsum & 0xffffffff) + (newcsum>>32);
+
+
+#ifdef CONFIG_ALPHA
+ /* This used to use csum_partial, which was wrong for several
+ * reasons including that different results are returned on
+ * different architectures. It isn't critical that we get exactly
+ * the same return value as before (we always csum_fold before
+ * testing, and that removes any differences). However as we
+ * know that csum_partial always returned a 16bit value on
+ * alphas, do a fold to maximise conformity to previous behaviour.
+ */
+ sb->sb_csum = md_csum_fold(disk_csum);
+#else
sb->sb_csum = disk_csum;
+#endif
return csum;
}

@@ -685,7 +712,7 @@ static int super_90_load(mdk_rdev_t *rde
if (sb->raid_disks <= 0)
goto abort;

- if (csum_fold(calc_sb_csum(sb)) != csum_fold(sb->sb_csum)) {
+ if (md_csum_fold(calc_sb_csum(sb)) != md_csum_fold(sb->sb_csum)) {
printk(KERN_WARNING "md: invalid superblock checksum on %s\n",
b);
goto abort;