On Fri, Jul 19, 2013 at 5:34 AM, Naoya Horiguchi
<n-horiguchi@xxxxxxxxxxxxx> 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
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> ---
> 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;
> + }
> + }
Can get_page do the work for us, like the following?
if (flags & FOLL_GET)
get_page(page);
> 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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