SBLOCKBLKSIZE
error = bread(mp->um_devvp, SBLOCK, SBLOCKBLKSIZE, NOCRED, &bp);
if ((error = bread(devvp, SBLOCK, SBLOCKBLKSIZE, NOCRED, &bp)) != 0)
if (PAGE_SIZE != SBLOCKBLKSIZE) {
if ((error = bread(devvp, SBLOCK, SBLOCKBLKSIZE, NOCRED, &bp)) != 0)