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 <n-horiguchi@xxxxxxxxxxxxx>
---
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
--
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