ffs_blkrelease_start
key = ffs_blkrelease_start(ump, ump->um_devvp, UFS_ROOTINO);
uint64_t ffs_blkrelease_start(struct ufsmount *, struct vnode *, ino_t);
key = ffs_blkrelease_start(ump, ump->um_devvp, ip->i_number);
key = ffs_blkrelease_start(ump, ITODEVVP(ip), ip->i_number);
key = ffs_blkrelease_start(ump, freeblks->fb_devvp, freeblks->fb_inum);
key = ffs_blkrelease_start(ump, freeblks->fb_devvp, freeblks->fb_inum);