Currently hugetlb_fault() checks at first whether pte of the faulted address is a migration or hwpoisoned entry, which means that we call huge_ptep_get() twice in single hugetlb_fault(). This is not optimized. The reason of this approach is that without checking at first, huge_pte_alloc() can trigger BUG_ON() because pmd_huge() returned false for non-present hugetlb entry.
With a previous patch in this series, pmd_huge() becomes to return true for non-present entry, so we no longer need this dirty workaround. Let's move the checking code to the proper place. Signed-off-by: Naoya Horiguchi <[email protected]> --- mm/hugetlb.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git mmotm-2014-11-26-15-45.orig/mm/hugetlb.c mmotm-2014-11-26-15-45/mm/hugetlb.c index a2bfd02e289f..6c38f9ad3d56 100644 --- mmotm-2014-11-26-15-45.orig/mm/hugetlb.c +++ mmotm-2014-11-26-15-45/mm/hugetlb.c @@ -3136,20 +3136,10 @@ 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; @@ -3176,12 +3166,16 @@ 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 @@ -3247,6 +3241,8 @@ 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); /* * Generally it's safe to hold refcount during waiting page lock. But * here we just wait to defer the next page fault to avoid busy loop and -- 2.2.0.rc0.2.gf745acb -- 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/
