Currently hugetlb_fault() checks at first whether pte of the faulted address is a migration or hwpoisoned entry. The reason of this approach is that without the checks, the BUG_ON() in huge_pte_alloc() is triggered, because it assumes that when pte is not none, it always points to a normal hugepage, which was correct originally but not after hugetlb supports page migration or hwpoison.
In order to iron out this weird workaround, this patch changes the wrongly assumed BUG_ON() in huge_pte_alloc(). This allows us to check pte_present() case only in proper place, which makes code simpler. Signed-off-by: Naoya Horiguchi <[email protected]> --- mm/hugetlb.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) diff --git mmotm-2014-09-25-16-28.orig/mm/hugetlb.c mmotm-2014-09-25-16-28/mm/hugetlb.c index 1ecb625bc498..e6543359be4d 100644 --- mmotm-2014-09-25-16-28.orig/mm/hugetlb.c +++ mmotm-2014-09-25-16-28/mm/hugetlb.c @@ -3130,20 +3130,10 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, struct hstate *h = hstate_vma(vma); struct address_space *mapping; int need_wait_lock = 0; + int need_wait_migration = 0; address &= huge_page_mask(h); - ptep = huge_pte_offset(mm, address); - if (ptep) { - entry = huge_ptep_get(ptep); - if (unlikely(is_hugetlb_entry_migration(entry))) { - migration_entry_wait_huge(vma, mm, ptep); - return 0; - } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) - return VM_FAULT_HWPOISON_LARGE | - VM_FAULT_SET_HINDEX(hstate_index(h)); - } - ptep = huge_pte_alloc(mm, address, huge_page_size(h)); if (!ptep) return VM_FAULT_OOM; @@ -3169,12 +3159,16 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, /* * entry could be a migration/hwpoison entry at this point, so this * check prevents the kernel from going below assuming that we have - * a active hugepage in pagecache. This goto expects the 2nd page fault, - * and is_hugetlb_entry_(migration|hwpoisoned) check will properly - * handle it. + * a active hugepage in pagecache. */ - if (!pte_present(entry)) + if (!pte_present(entry)) { + if (is_hugetlb_entry_migration(entry)) + need_wait_migration = 1; + else if (is_hugetlb_entry_hwpoisoned(entry)) + ret = VM_FAULT_HWPOISON_LARGE | + VM_FAULT_SET_HINDEX(hstate_index(h)); goto out_mutex; + } /* * If we are going to COW the mapping later, we examine the pending @@ -3242,6 +3236,8 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, } out_mutex: mutex_unlock(&htlb_fault_mutex_table[hash]); + if (need_wait_migration) + migration_entry_wait_huge(vma, mm, ptep); if (need_wait_lock) wait_on_page_locked(page); return ret; @@ -3664,7 +3660,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, pte = (pte_t *)pmd_alloc(mm, pud, addr); } } - BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte)); + BUG_ON(pte && !pte_none(*pte) && pte_present(*pte) && !pte_huge(*pte)); return pte; } -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
