lfs_gatherblock
if (lfs_gatherblock(sp, bp)) {
int lfs_gatherblock(struct segment *, struct ubuf *);
int lfs_gatherblock(struct segment *, struct buf *, kmutex_t *);
while (lfs_gatherblock(fs->lfs_sp, bp, &bufcache_lock)) {
if (lfs_gatherblock(sp, bp, &bufcache_lock)) {
while (lfs_gatherblock(sp, bp, NULL))