On Mon, Jun 20, 2016 at 12:32:01PM +0300, Kirill A. Shutemov wrote:
> > +void split_huge_pmd_address_freeze(struct vm_area_struct *vma,
> > + unsigned long address, struct page *page)
> > +{
> > + pgd_t *pgd;
> > + pud_t *pud;
> > + pmd_t *pmd;
> > +
> > + pgd = pgd_offset(vma->vm_mm, address);
> > + if (!pgd_present(*pgd))
> > + return;
> > +
> > + pud = pud_offset(pgd, address);
> > + if (!pud_present(*pud))
> > + return;
> > +
> > + pmd = pmd_offset(pud, address);
> > + __split_huge_pmd(vma, pmd, address, page, true);
> > }
>
> I don't see a reason to introduce new function. Just move the page
> check under ptl from split_huge_pmd_address() and that should be enough.
>
> Or am I missing something?
I'm talking about something like patch below. Could you test it?
If it works fine to you, feel free to submit with my Signed-off-by.
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index eb810816bbc6..92ce91c03cd0 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -98,7 +98,7 @@ static inline int split_huge_page(struct page *page)
void deferred_split_huge_page(struct page *page);
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
- unsigned long address, bool freeze);
+ unsigned long address, bool freeze, struct page *page);
#define split_huge_pmd(__vma, __pmd, __address) \
do { \
@@ -106,7 +106,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
if (pmd_trans_huge(*____pmd) \
|| pmd_devmap(*____pmd)) \
__split_huge_pmd(__vma, __pmd, __address, \
- false); \
+ false, NULL); \
} while (0)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index eaf3a4a655a6..2297aa41581e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1638,7 +1638,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
}
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
- unsigned long address, bool freeze)
+ unsigned long address, bool freeze, struct page *page)
{
spinlock_t *ptl;
struct mm_struct *mm = vma->vm_mm;
@@ -1646,8 +1646,17 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
ptl = pmd_lock(mm, pmd);
+
+ /*
+ * If caller asks to setup a migration entries, we need a page to check
+ * pmd against. Otherwise we can end up replacing wrong page.
+ */
+ VM_BUG_ON(freeze && !page);
+ if (page && page != pmd_page(*pmd))
+ goto out;
+
if (pmd_trans_huge(*pmd)) {
- struct page *page = pmd_page(*pmd);
+ page = pmd_page(*pmd);
if (PageMlocked(page))
clear_page_mlock(page);
} else if (!pmd_devmap(*pmd))
@@ -1678,20 +1687,12 @@ void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
return;
/*
- * If caller asks to setup a migration entries, we need a page to check
- * pmd against. Otherwise we can end up replacing wrong page.
- */
- VM_BUG_ON(freeze && !page);
- if (page && page != pmd_page(*pmd))
- return;
-
- /*
* Caller holds the mmap_sem write mode or the anon_vma lock,
* so a huge pmd cannot materialize from under us (khugepaged
* holds both the mmap_sem write mode and the anon_vma lock
* write mode).
*/
- __split_huge_pmd(vma, pmd, address, freeze);
+ __split_huge_pmd(vma, pmd, address, freeze, page);
}
void vma_adjust_trans_huge(struct vm_area_struct *vma,
--
Kirill A. Shutemov
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