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mm, thp: fix collapsing of hugepages on madvise

If an anonymous mapping is not allowed to fault thp memory and then madvise(MADV_HUGEPAGE) is used after fault, khugepaged will never collapse this memory into thp memory. This occurs because the madvise(2) handler for thp, hugepage_madvise(), clears VM_NOHUGEPAGE on the stack and it isn't stored in vma->vm_flags until the final action of madvise_behavior(). This causes the khugepaged_enter_vma_merge() to be a no-op in hugepage_madvise() when the vma had previously had VM_NOHUGEPAGE set. Fix this by passing the correct vma flags to the khugepaged mm slot handler. There's no chance khugepaged can run on this vma until after madvise_behavior() returns since we hold mm->mmap_sem. It would be possible to clear VM_NOHUGEPAGE directly from vma->vm_flags in hugepage_advise(), but I didn't want to introduce special case behavior into madvise_behavior(). I think it's best to just let it always set vma->vm_flags itself.

David Rientjes committed 12 years ago

Commit 6d50e601 parent 47f29df3 files · +20 −16Browse files

Unified · Split

3 files
  1. include/linux/khugepaged.h +10 −7
  2. mm/huge_memory.c +6 −5
  3. mm/mmap.c +4 −4
include/linux/khugepaged.h+10−7
@@ -6,7 +6,8 @@ · 5 unmodified lines
6#ifdef CONFIG_TRANSPARENT_HUGEPAGE6#ifdef CONFIG_TRANSPARENT_HUGEPAGE
7extern int __khugepaged_enter(struct mm_struct *mm);7extern int __khugepaged_enter(struct mm_struct *mm);
8extern void __khugepaged_exit(struct mm_struct *mm);8extern void __khugepaged_exit(struct mm_struct *mm);
9extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma);9extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
10 unsigned long vm_flags);
10 11
11#define khugepaged_enabled() \12#define khugepaged_enabled() \
12 (transparent_hugepage_flags & \13 (transparent_hugepage_flags & \
@@ -35,13 +36,13 @@ static inline void khugepaged_exit(struct mm_struct *mm) · 22 unmodified lines
35 __khugepaged_exit(mm);36 __khugepaged_exit(mm);
36}37}
37 38
38static inline int khugepaged_enter(struct vm_area_struct *vma)39static inline int khugepaged_enter(struct vm_area_struct *vma,
40 unsigned long vm_flags)
39{41{
40 if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))42 if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
41 if ((khugepaged_always() ||43 if ((khugepaged_always() ||
42 (khugepaged_req_madv() &&44 (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
43 vma->vm_flags & VM_HUGEPAGE)) &&45 !(vm_flags & VM_NOHUGEPAGE))
44 !(vma->vm_flags & VM_NOHUGEPAGE))
45 if (__khugepaged_enter(vma->vm_mm))46 if (__khugepaged_enter(vma->vm_mm))
46 return -ENOMEM;47 return -ENOMEM;
47 return 0;48 return 0;
@@ -54,11 +55,13 @@ static inline int khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm) · 6 unmodified lines
54static inline void khugepaged_exit(struct mm_struct *mm)55static inline void khugepaged_exit(struct mm_struct *mm)
55{56{
56}57}
57static inline int khugepaged_enter(struct vm_area_struct *vma)58static inline int khugepaged_enter(struct vm_area_struct *vma,
59 unsigned long vm_flags)
58{60{
59 return 0;61 return 0;
60}62}
61static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma)63static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
64 unsigned long vm_flags)
62{65{
63 return 0;66 return 0;
64}67}
mm/huge_memory.c+6−5
@@ -803,7 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, · 802 unmodified lines
803 return VM_FAULT_FALLBACK;803 return VM_FAULT_FALLBACK;
804 if (unlikely(anon_vma_prepare(vma)))804 if (unlikely(anon_vma_prepare(vma)))
805 return VM_FAULT_OOM;805 return VM_FAULT_OOM;
806 if (unlikely(khugepaged_enter(vma)))806 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
807 return VM_FAULT_OOM;807 return VM_FAULT_OOM;
808 if (!(flags & FAULT_FLAG_WRITE) &&808 if (!(flags & FAULT_FLAG_WRITE) &&
809 transparent_hugepage_use_zero_page()) {809 transparent_hugepage_use_zero_page()) {
@@ -1970,7 +1970,7 @@ int hugepage_madvise(struct vm_area_struct *vma, · 1160 unmodified lines
1970 * register it here without waiting a page fault that1970 * register it here without waiting a page fault that
1971 * may not happen any time soon.1971 * may not happen any time soon.
1972 */1972 */
1973 if (unlikely(khugepaged_enter_vma_merge(vma)))1973 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1974 return -ENOMEM;1974 return -ENOMEM;
1975 break;1975 break;
1976 case MADV_NOHUGEPAGE:1976 case MADV_NOHUGEPAGE:
@@ -2071,7 +2071,8 @@ int __khugepaged_enter(struct mm_struct *mm) · 94 unmodified lines
2071 return 0;2071 return 0;
2072}2072}
2073 2073
2074int khugepaged_enter_vma_merge(struct vm_area_struct *vma)2074int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2075 unsigned long vm_flags)
2075{2076{
2076 unsigned long hstart, hend;2077 unsigned long hstart, hend;
2077 if (!vma->anon_vma)2078 if (!vma->anon_vma)
@@ -2083,11 +2084,11 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma) · 5 unmodified lines
2083 if (vma->vm_ops)2084 if (vma->vm_ops)
2084 /* khugepaged not yet working on file or special mappings */2085 /* khugepaged not yet working on file or special mappings */
2085 return 0;2086 return 0;
2086 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);2087 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
2087 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;2088 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2088 hend = vma->vm_end & HPAGE_PMD_MASK;2089 hend = vma->vm_end & HPAGE_PMD_MASK;
2089 if (hstart < hend)2090 if (hstart < hend)
2090 return khugepaged_enter(vma);2091 return khugepaged_enter(vma, vm_flags);
2091 return 0;2092 return 0;
2092}2093}
2093 2094
mm/mmap.c+4−4
@@ -1080,7 +1080,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, · 1079 unmodified lines
1080 end, prev->vm_pgoff, NULL);1080 end, prev->vm_pgoff, NULL);
1081 if (err)1081 if (err)
1082 return NULL;1082 return NULL;
1083 khugepaged_enter_vma_merge(prev);1083 khugepaged_enter_vma_merge(prev, vm_flags);
1084 return prev;1084 return prev;
1085 }1085 }
1086 1086
@@ -1099,7 +1099,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, · 12 unmodified lines
1099 next->vm_pgoff - pglen, NULL);1099 next->vm_pgoff - pglen, NULL);
1100 if (err)1100 if (err)
1101 return NULL;1101 return NULL;
1102 khugepaged_enter_vma_merge(area);1102 khugepaged_enter_vma_merge(area, vm_flags);
1103 return area;1103 return area;
1104 }1104 }
1105 1105
@@ -2208,7 +2208,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) · 1102 unmodified lines
2208 }2208 }
2209 }2209 }
2210 vma_unlock_anon_vma(vma);2210 vma_unlock_anon_vma(vma);
2211 khugepaged_enter_vma_merge(vma);2211 khugepaged_enter_vma_merge(vma, vma->vm_flags);
2212 validate_mm(vma->vm_mm);2212 validate_mm(vma->vm_mm);
2213 return error;2213 return error;
2214}2214}
@@ -2277,7 +2277,7 @@ int expand_downwards(struct vm_area_struct *vma, · 62 unmodified lines
2277 }2277 }
2278 }2278 }
2279 vma_unlock_anon_vma(vma);2279 vma_unlock_anon_vma(vma);
2280 khugepaged_enter_vma_merge(vma);2280 khugepaged_enter_vma_merge(vma, vma->vm_flags);
2281 validate_mm(vma->vm_mm);2281 validate_mm(vma->vm_mm);
2282 return error;2282 return error;
2283}2283}