PREALLOCATED_PMDS
for (i = 0; i < PREALLOCATED_PMDS; i++)
for (i = 0; i < PREALLOCATED_PMDS; i++, pud++) {
pmd_t *pmds[PREALLOCATED_PMDS];
preallocate_pmds(mm, pmds, PREALLOCATED_PMDS) != 0)
free_pmds(mm, pmds, PREALLOCATED_PMDS);