xfs: xfs_sb_read_verify() doesn't flag bad crcs on primary sb

My earlier commit 10e6e65 deserves a layer or two of brown paper
bags.  The logic in that commit means that a CRC failure on the
primary superblock will *never* result in an error return.

Hopefully this fixes it, so that we always return the error
if it's a primary superblock, otherwise only if the filesystem
has CRCs enabled.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_sb.c

@@ -614,7 +614,7 @@ xfs_sb_read_verify(
 		if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
 				      offsetof(struct xfs_sb, sb_crc))) {
 			/* Only fail bad secondaries on a known V5 filesystem */
-			if (bp->b_bn != XFS_SB_DADDR &&
+			if (bp->b_bn == XFS_SB_DADDR ||
 			    xfs_sb_version_hascrc(&mp->m_sb)) {
 				error = EFSCORRUPTED;
 				goto out_error;