The patch titled
Subject: mm/hugetlb: fix suboptimal migration/hwpoisoned entry check
has been added to the -mm tree. Its filename is
mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check.patch
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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm/hugetlb: fix suboptimal migration/hwpoisoned entry check
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>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: James Hogan <james.hogan@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 26 +++++++++++---------------
1 file changed, 11 insertions(+), 15 deletions(-)
diff -puN mm/hugetlb.c~mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check
+++ a/mm/hugetlb.c
@@ -3136,20 +3136,10 @@ int hugetlb_fault(struct mm_struct *mm,
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,
/*
* 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 @@ out_ptl:
}
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
_
Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are
mm-add-kpf_zero_page-flag-for-proc-kpageflags.patch
mm-hugetlb-reduce-arch-dependent-code-around-follow_huge_.patch
mm-hugetlb-pmd_huge-returns-true-for-non-present-hugepage.patch
mm-hugetlb-take-page-table-lock-in-follow_huge_pmd.patch
mm-hugetlb-fix-getting-refcount-0-page-in-hugetlb_fault.patch
mm-hugetlb-add-migration-hwpoisoned-entry-check-in-hugetlb_change_protection.patch
mm-hugetlb-add-migration-entry-check-in-__unmap_hugepage_range.patch
mm-hugetlb-fix-suboptimal-migration-hwpoisoned-entry-check.patch
mm-hugetlb-cleanup-and-rename-is_hugetlb_entry_migrationhwpoisoned.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
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