Re: [PATCH 3/8] migrate: add hugepage migration code to migrate_pages()

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

On Thu, Jul 18, 2013 at 05:34:27PM -0400, Naoya Horiguchi wrote:
>This patch extends check_range() to handle vma with VM_HUGETLB set.
>We will be able to migrate hugepage with migrate_pages(2) after
>applying the enablement patch which comes later in this series.
>
>Note that for larger hugepages (covered by pud entries, 1GB for
>x86_64 for example), we simply skip it now.
>
>Note that using pmd_huge/pud_huge assumes that hugepages are pointed to
>by pmd/pud. This is not true in some architectures implementing hugepage
>with other mechanisms like ia64, but it's OK because pmd_huge/pud_huge
>simply return 0 in such arch and page walker simply ignores such hugepages.
>
>ChangeLog v3:
> - revert introducing migrate_movable_pages
> - use isolate_huge_page
>
>ChangeLog v2:
> - remove unnecessary extern
> - fix page table lock in check_hugetlb_pmd_range
> - updated description and renamed patch title
>

Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>

>Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>---
> mm/mempolicy.c | 39 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 5 deletions(-)
>
>diff --git v3.11-rc1.orig/mm/mempolicy.c v3.11-rc1/mm/mempolicy.c
>index 7431001..f3b65c0 100644
>--- v3.11-rc1.orig/mm/mempolicy.c
>+++ v3.11-rc1/mm/mempolicy.c
>@@ -512,6 +512,27 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> 	return addr != end;
> }
>
>+static void check_hugetlb_pmd_range(struct vm_area_struct *vma, pmd_t *pmd,
>+		const nodemask_t *nodes, unsigned long flags,
>+				    void *private)
>+{
>+#ifdef CONFIG_HUGETLB_PAGE
>+	int nid;
>+	struct page *page;
>+
>+	spin_lock(&vma->vm_mm->page_table_lock);
>+	page = pte_page(huge_ptep_get((pte_t *)pmd));
>+	nid = page_to_nid(page);
>+	if (node_isset(nid, *nodes) != !!(flags & MPOL_MF_INVERT)
>+	    && ((flags & MPOL_MF_MOVE && page_mapcount(page) == 1)
>+		|| flags & MPOL_MF_MOVE_ALL))
>+		isolate_huge_page(page, private);
>+	spin_unlock(&vma->vm_mm->page_table_lock);
>+#else
>+	BUG();
>+#endif
>+}
>+
> static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud,
> 		unsigned long addr, unsigned long end,
> 		const nodemask_t *nodes, unsigned long flags,
>@@ -523,6 +544,11 @@ static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud,
> 	pmd = pmd_offset(pud, addr);
> 	do {
> 		next = pmd_addr_end(addr, end);
>+		if (pmd_huge(*pmd) && is_vm_hugetlb_page(vma)) {
>+			check_hugetlb_pmd_range(vma, pmd, nodes,
>+						flags, private);
>+			continue;
>+		}
> 		split_huge_page_pmd(vma, addr, pmd);
> 		if (pmd_none_or_trans_huge_or_clear_bad(pmd))
> 			continue;
>@@ -544,6 +570,8 @@ static inline int check_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
> 	pud = pud_offset(pgd, addr);
> 	do {
> 		next = pud_addr_end(addr, end);
>+		if (pud_huge(*pud) && is_vm_hugetlb_page(vma))
>+			continue;
> 		if (pud_none_or_clear_bad(pud))
> 			continue;
> 		if (check_pmd_range(vma, pud, addr, next, nodes,
>@@ -635,9 +663,6 @@ check_range(struct mm_struct *mm, unsigned long start, unsigned long end,
> 				return ERR_PTR(-EFAULT);
> 		}
>
>-		if (is_vm_hugetlb_page(vma))
>-			goto next;
>-
> 		if (flags & MPOL_MF_LAZY) {
> 			change_prot_numa(vma, start, endvma);
> 			goto next;
>@@ -986,7 +1011,11 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
>
> static struct page *new_node_page(struct page *page, unsigned long node, int **x)
> {
>-	return alloc_pages_exact_node(node, GFP_HIGHUSER_MOVABLE, 0);
>+	if (PageHuge(page))
>+		return alloc_huge_page_node(page_hstate(compound_head(page)),
>+					node);
>+	else
>+		return alloc_pages_exact_node(node, GFP_HIGHUSER_MOVABLE, 0);
> }
>
> /*
>@@ -1016,7 +1045,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> 		err = migrate_pages(&pagelist, new_node_page, dest,
> 					MIGRATE_SYNC, MR_SYSCALL);
> 		if (err)
>-			putback_lru_pages(&pagelist);
>+			putback_movable_pages(&pagelist);
> 	}
>
> 	return err;
>-- 
>1.8.3.1
>
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