mm, thp: fix collapsing of hugepages on madvise

commit 6d50e60cd2edb5a57154db5a6f64eef5aa59b751 upstream.

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.

Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Suleiman Souhlal <suleiman@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index 6b394f0..eeb3079 100644 (file)
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -6,7 +6,8 @@
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern int __khugepaged_enter(struct mm_struct *mm);
 extern void __khugepaged_exit(struct mm_struct *mm);
-extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma);
+extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+                                     unsigned long vm_flags);
 
 #define khugepaged_enabled()                                          \
        (transparent_hugepage_flags &                                  \
@@ -35,13 +36,13 @@ static inline void khugepaged_exit(struct mm_struct *mm)
                __khugepaged_exit(mm);
 }
 
-static inline int khugepaged_enter(struct vm_area_struct *vma)
+static inline int khugepaged_enter(struct vm_area_struct *vma,
+                                  unsigned long vm_flags)
 {
        if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
                if ((khugepaged_always() ||
-                    (khugepaged_req_madv() &&
-                     vma->vm_flags & VM_HUGEPAGE)) &&
-                   !(vma->vm_flags & VM_NOHUGEPAGE))
+                    (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
+                   !(vm_flags & VM_NOHUGEPAGE))
                        if (__khugepaged_enter(vma->vm_mm))
                                return -ENOMEM;
        return 0;
@@ -54,11 +55,13 @@ static inline int khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 static inline void khugepaged_exit(struct mm_struct *mm)
 {
 }
-static inline int khugepaged_enter(struct vm_area_struct *vma)
+static inline int khugepaged_enter(struct vm_area_struct *vma,
+                                  unsigned long vm_flags)
 {
        return 0;
 }
-static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
+static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+                                            unsigned long vm_flags)
 {
        return 0;
 }

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ed0ed8a..79166c2 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -682,7 +682,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
        if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
                if (unlikely(anon_vma_prepare(vma)))
                        return VM_FAULT_OOM;
-               if (unlikely(khugepaged_enter(vma)))
+               if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
                        return VM_FAULT_OOM;
                page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
                                          vma, haddr, numa_node_id(), 0);
@@ -1493,7 +1493,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
                 * register it here without waiting a page fault that
                 * may not happen any time soon.
                 */
-               if (unlikely(khugepaged_enter_vma_merge(vma)))
+               if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
                        return -ENOMEM;
                break;
        case MADV_NOHUGEPAGE:
@@ -1625,7 +1625,8 @@ int __khugepaged_enter(struct mm_struct *mm)
        return 0;
 }
 
-int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
+int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+                              unsigned long vm_flags)
 {
        unsigned long hstart, hend;
        if (!vma->anon_vma)
@@ -1641,11 +1642,11 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
         * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
         * true too, verify it here.
         */
-       VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
+       VM_BUG_ON(is_linear_pfn_mapping(vma) || vm_flags & VM_NO_THP);
        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
        hend = vma->vm_end & HPAGE_PMD_MASK;
        if (hstart < hend)
-               return khugepaged_enter(vma);
+               return khugepaged_enter(vma, vm_flags);
        return 0;
 }
 

diff --cc mm/mmap.c
Simple merge