Re: [PATCH 4/8] migrate: add hugepage migration code to move_pages()

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

On Thu, Jul 18, 2013 at 05:34:28PM -0400, Naoya Horiguchi wrote:
>This patch extends move_pages() to handle vma with VM_HUGETLB set.
>We will be able to migrate hugepage with move_pages(2) after
>applying the enablement patch which comes later in this series.
>
>We avoid getting refcount on tail pages of hugepage, because unlike thp,
>hugepage is not split and we need not care about races with splitting.
>
>And migration of larger (1GB for x86_64) hugepage are not enabled.
>
>ChangeLog v3:
> - revert introducing migrate_movable_pages
> - follow_page_mask(FOLL_GET) returns NULL for tail pages
> - use isolate_huge_page
>
>ChangeLog v2:
> - 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/memory.c  | 12 ++++++++++--
> mm/migrate.c | 13 +++++++++++--
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
>diff --git v3.11-rc1.orig/mm/memory.c v3.11-rc1/mm/memory.c
>index 1ce2e2a..8c9a2cb 100644
>--- v3.11-rc1.orig/mm/memory.c
>+++ v3.11-rc1/mm/memory.c
>@@ -1496,7 +1496,8 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
> 	if (pud_none(*pud))
> 		goto no_page_table;
> 	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
>-		BUG_ON(flags & FOLL_GET);
>+		if (flags & FOLL_GET)
>+			goto out;
> 		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
> 		goto out;
> 	}
>@@ -1507,8 +1508,15 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
> 	if (pmd_none(*pmd))
> 		goto no_page_table;
> 	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
>-		BUG_ON(flags & FOLL_GET);
> 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
>+		if (flags & FOLL_GET) {
>+			if (PageHead(page))
>+				get_page_foll(page);
>+			else {
>+				page = NULL;
>+				goto out;
>+			}
>+		}
> 		goto out;
> 	}
> 	if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
>diff --git v3.11-rc1.orig/mm/migrate.c v3.11-rc1/mm/migrate.c
>index 3ec47d3..d313737 100644
>--- v3.11-rc1.orig/mm/migrate.c
>+++ v3.11-rc1/mm/migrate.c
>@@ -1092,7 +1092,11 @@ static struct page *new_page_node(struct page *p, unsigned long private,
>
> 	*result = &pm->status;
>
>-	return alloc_pages_exact_node(pm->node,
>+	if (PageHuge(p))
>+		return alloc_huge_page_node(page_hstate(compound_head(p)),
>+					pm->node);
>+	else
>+		return alloc_pages_exact_node(pm->node,
> 				GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
> }
>
>@@ -1152,6 +1156,11 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
> 				!migrate_all)
> 			goto put_and_set;
>
>+		if (PageHuge(page)) {
>+			isolate_huge_page(page, &pagelist);
>+			goto put_and_set;
>+		}
>+
> 		err = isolate_lru_page(page);
> 		if (!err) {
> 			list_add_tail(&page->lru, &pagelist);
>@@ -1174,7 +1183,7 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
> 		err = migrate_pages(&pagelist, new_page_node,
> 				(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
> 		if (err)
>-			putback_lru_pages(&pagelist);
>+			putback_movable_pages(&pagelist);
> 	}
>
> 	up_read(&mm->mmap_sem);
>-- 
>1.8.3.1
>
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