2 files changed, 231 insertions, 19 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a73dbdc..0fa9de8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2217,6 +2217,19 @@ nomem:
 	return -ENOMEM;
 }
 
+static int is_hugetlb_entry_migration(pte_t pte)
+{
+	swp_entry_t swp;
+
+	if (huge_pte_none(pte) || pte_present(pte))
+		return 0;
+	swp = pte_to_swp_entry(pte);
+	if (non_swap_entry(swp) && is_migration_entry(swp)) {
+		return 1;
+	} else
+		return 0;
+}
+
 static int is_hugetlb_entry_hwpoisoned(pte_t pte)
 {
 	swp_entry_t swp;
@@ -2648,7 +2661,10 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	ptep = huge_pte_offset(mm, address);
 	if (ptep) {
 		entry = huge_ptep_get(ptep);
-		if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
+		if (unlikely(is_hugetlb_entry_migration(entry))) {
+			migration_entry_wait(mm, (pmd_t *)ptep, address);
+			return 0;
+		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
 			return VM_FAULT_HWPOISON;
 	}
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 38e7cad..55dbc45 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -32,6 +32,7 @@
 #include <linux/security.h>
 #include <linux/memcontrol.h>
 #include <linux/syscalls.h>
+#include <linux/hugetlb.h>
 #include <linux/gfp.h>
 
 #include "internal.h"
@@ -95,26 +96,34 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 	pte_t *ptep, pte;
  	spinlock_t *ptl;
 
- 	pgd = pgd_offset(mm, addr);
-	if (!pgd_present(*pgd))
-		goto out;
+	if (unlikely(PageHuge(new))) {
+		ptep = huge_pte_offset(mm, addr);
+		if (!ptep)
+			goto out;
+		ptl = &mm->page_table_lock;
+	} else {
+		pgd = pgd_offset(mm, addr);
+		if (!pgd_present(*pgd))
+			goto out;
 
-	pud = pud_offset(pgd, addr);
-	if (!pud_present(*pud))
-		goto out;
+		pud = pud_offset(pgd, addr);
+		if (!pud_present(*pud))
+			goto out;
 
-	pmd = pmd_offset(pud, addr);
-	if (!pmd_present(*pmd))
-		goto out;
+		pmd = pmd_offset(pud, addr);
+		if (!pmd_present(*pmd))
+			goto out;
 
-	ptep = pte_offset_map(pmd, addr);
+		ptep = pte_offset_map(pmd, addr);
 
-	if (!is_swap_pte(*ptep)) {
-		pte_unmap(ptep);
-		goto out;
- 	}
+		if (!is_swap_pte(*ptep)) {
+			pte_unmap(ptep);
+			goto out;
+		}
+
+		ptl = pte_lockptr(mm, pmd);
+	}
 
- 	ptl = pte_lockptr(mm, pmd);
  	spin_lock(ptl);
 	pte = *ptep;
 	if (!is_swap_pte(pte))
@@ -130,10 +139,17 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
 	if (is_write_migration_entry(entry))
 		pte = pte_mkwrite(pte);
+	if (PageHuge(new))
+		pte = pte_mkhuge(pte);
 	flush_cache_page(vma, addr, pte_pfn(pte));
 	set_pte_at(mm, addr, ptep, pte);
 
-	if (PageAnon(new))
+	if (PageHuge(new)) {
+		if (PageAnon(new))
+			hugepage_add_anon_rmap(new, vma, addr);
+		else
+			page_dup_rmap(new);
+	} else if (PageAnon(new))
 		page_add_anon_rmap(new, vma, addr);
 	else
 		page_add_file_rmap(new);
@@ -276,11 +292,59 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 }
 
 /*
+ * The expected number of remaining references is the same as that
+ * of migrate_page_move_mapping().
+ */
+int migrate_huge_page_move_mapping(struct address_space *mapping,
+				   struct page *newpage, struct page *page)
+{
+	int expected_count;
+	void **pslot;
+
+	if (!mapping) {
+		if (page_count(page) != 1)
+			return -EAGAIN;
+		return 0;
+	}
+
+	spin_lock_irq(&mapping->tree_lock);
+
+	pslot = radix_tree_lookup_slot(&mapping->page_tree,
+					page_index(page));
+
+	expected_count = 2 + page_has_private(page);
+	if (page_count(page) != expected_count ||
+	    (struct page *)radix_tree_deref_slot(pslot) != page) {
+		spin_unlock_irq(&mapping->tree_lock);
+		return -EAGAIN;
+	}
+
+	if (!page_freeze_refs(page, expected_count)) {
+		spin_unlock_irq(&mapping->tree_lock);
+		return -EAGAIN;
+	}
+
+	get_page(newpage);
+
+	radix_tree_replace_slot(pslot, newpage);
+
+	page_unfreeze_refs(page, expected_count);
+
+	__put_page(page);
+
+	spin_unlock_irq(&mapping->tree_lock);
+	return 0;
+}
+
+/*
  * Copy the page to its new location
  */
-static void migrate_page_copy(struct page *newpage, struct page *page)
+void migrate_page_copy(struct page *newpage, struct page *page)
 {
-	copy_highpage(newpage, page);
+	if (PageHuge(page))
+		copy_huge_page(newpage, page);
+	else
+		copy_highpage(newpage, page);
 
 	if (PageError(page))
 		SetPageError(newpage);
@@ -724,6 +788,92 @@ move_newpage:
 }
 
 /*
+ * Counterpart of unmap_and_move_page() for hugepage migration.
+ *
+ * This function doesn't wait the completion of hugepage I/O
+ * because there is no race between I/O and migration for hugepage.
+ * Note that currently hugepage I/O occurs only in direct I/O
+ * where no lock is held and PG_writeback is irrelevant,
+ * and writeback status of all subpages are counted in the reference
+ * count of the head page (i.e. if all subpages of a 2MB hugepage are
+ * under direct I/O, the reference of the head page is 512 and a bit more.)
+ * This means that when we try to migrate hugepage whose subpages are
+ * doing direct I/O, some references remain after try_to_unmap() and
+ * hugepage migration fails without data corruption.
+ *
+ * There is also no race when direct I/O is issued on the page under migration,
+ * because then pte is replaced with migration swap entry and direct I/O code
+ * will wait in the page fault for migration to complete.
+ */
+static int unmap_and_move_huge_page(new_page_t get_new_page,
+				unsigned long private, struct page *hpage,
+				int force, int offlining)
+{
+	int rc = 0;
+	int *result = NULL;
+	struct page *new_hpage = get_new_page(hpage, private, &result);
+	int rcu_locked = 0;
+	struct anon_vma *anon_vma = NULL;
+
+	if (!new_hpage)
+		return -ENOMEM;
+
+	rc = -EAGAIN;
+
+	if (!trylock_page(hpage)) {
+		if (!force)
+			goto out;
+		lock_page(hpage);
+	}
+
+	if (PageAnon(hpage)) {
+		rcu_read_lock();
+		rcu_locked = 1;
+
+		if (page_mapped(hpage)) {
+			anon_vma = page_anon_vma(hpage);
+			atomic_inc(&anon_vma->external_refcount);
+		}
+	}
+
+	try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
+
+	if (!page_mapped(hpage))
+		rc = move_to_new_page(new_hpage, hpage, 1);
+
+	if (rc)
+		remove_migration_ptes(hpage, hpage);
+
+	if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount,
+					    &anon_vma->lock)) {
+		int empty = list_empty(&anon_vma->head);
+		spin_unlock(&anon_vma->lock);
+		if (empty)
+			anon_vma_free(anon_vma);
+	}
+
+	if (rcu_locked)
+		rcu_read_unlock();
+out:
+	unlock_page(hpage);
+
+	if (rc != -EAGAIN) {
+		list_del(&hpage->lru);
+		put_page(hpage);
+	}
+
+	put_page(new_hpage);
+
+	if (result) {
+		if (rc)
+			*result = rc;
+		else
+			*result = page_to_nid(new_hpage);
+	}
+	return rc;
+}
+
+/*
  * migrate_pages
  *
  * The function takes one list of pages to migrate and a function
@@ -788,6 +938,52 @@ out:
 	return nr_failed + retry;
 }
 
+int migrate_huge_pages(struct list_head *from,
+		new_page_t get_new_page, unsigned long private, int offlining)
+{
+	int retry = 1;
+	int nr_failed = 0;
+	int pass = 0;
+	struct page *page;
+	struct page *page2;
+	int rc;
+
+	for (pass = 0; pass < 10 && retry; pass++) {
+		retry = 0;
+
+		list_for_each_entry_safe(page, page2, from, lru) {
+			cond_resched();
+
+			rc = unmap_and_move_huge_page(get_new_page,
+					private, page, pass > 2, offlining);
+
+			switch(rc) {
+			case -ENOMEM:
+				goto out;
+			case -EAGAIN:
+				retry++;
+				break;
+			case 0:
+				break;
+			default:
+				/* Permanent failure */
+				nr_failed++;
+				break;
+			}
+		}
+	}
+	rc = 0;
+out:
+
+	list_for_each_entry_safe(page, page2, from, lru)
+		put_page(page);
+
+	if (rc)
+		return rc;
+
+	return nr_failed + retry;
+}
+
 #ifdef CONFIG_NUMA
 /*
  * Move a list of individual pages