mm/migration: return errno when isolate_huge_page failed

[ Upstream commit 7ce82f4c3f ]

We might fail to isolate huge page due to e.g.  the page is under
migration which cleared HPageMigratable.  We should return errno in this
case rather than always return 1 which could confuse the user, i.e.  the
caller might think all of the memory is migrated while the hugetlb page is
left behind.  We make the prototype of isolate_huge_page consistent with
isolate_lru_page as suggested by Huang Ying and rename isolate_huge_page
to isolate_hugetlb as suggested by Muchun to improve the readability.

Link: https://lkml.kernel.org/r/20220530113016.16663-4-linmiaohe@huawei.com
Fixes: e8db67eb0d ("mm: migrate: move_pages() supports thp migration")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: Huang Ying <ying.huang@intel.com>
Reported-by: kernel test robot <lkp@intel.com> (build error)
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/linux/hugetlb.h

@@ -167,7 +167,7 @@ bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
 						vm_flags_t vm_flags);
 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 						long freed);
-bool isolate_huge_page(struct page *page, struct list_head *list);
+int isolate_hugetlb(struct page *page, struct list_head *list);
 int get_hwpoison_huge_page(struct page *page, bool *hugetlb);
 int get_huge_page_for_hwpoison(unsigned long pfn, int flags);
 void putback_active_hugepage(struct page *page);
@@ -369,9 +369,9 @@ static inline pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr,
 	return NULL;
 }
 
-static inline bool isolate_huge_page(struct page *page, struct list_head *list)
+static inline int isolate_hugetlb(struct page *page, struct list_head *list)
 {
-	return false;
+	return -EBUSY;
 }
 
 static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb)

mm/gup.c

@@ -1795,7 +1795,7 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
 		 * Try to move out any movable page before pinning the range.
 		 */
 		if (folio_test_hugetlb(folio)) {
-			if (!isolate_huge_page(&folio->page,
+			if (isolate_hugetlb(&folio->page,
 						&movable_page_list))
 				isolation_error_count++;
 			continue;

mm/hugetlb.c

@@ -2758,8 +2758,7 @@ retry:
 		 * Fail with -EBUSY if not possible.
 		 */
 		spin_unlock_irq(&hugetlb_lock);
-		if (!isolate_huge_page(old_page, list))
+		ret = isolate_hugetlb(old_page, list);
-			ret = -EBUSY;
 		spin_lock_irq(&hugetlb_lock);
 		goto free_new;
 	} else if (!HPageFreed(old_page)) {
@@ -2835,7 +2834,7 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 	if (hstate_is_gigantic(h))
 		return -ENOMEM;
 
-	if (page_count(head) && isolate_huge_page(head, list))
+	if (page_count(head) && !isolate_hugetlb(head, list))
 		ret = 0;
 	else if (!page_count(head))
 		ret = alloc_and_dissolve_huge_page(h, head, list);
@@ -6758,15 +6757,15 @@ follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int fla
 	return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
 }
 
-bool isolate_huge_page(struct page *page, struct list_head *list)
+int isolate_hugetlb(struct page *page, struct list_head *list)
 {
-	bool ret = true;
+	int ret = 0;
 
 	spin_lock_irq(&hugetlb_lock);
 	if (!PageHeadHuge(page) ||
 	    !HPageMigratable(page) ||
 	    !get_page_unless_zero(page)) {
-		ret = false;
+		ret = -EBUSY;
 		goto unlock;
 	}
 	ClearHPageMigratable(page);

mm/memory-failure.c

@@ -2211,7 +2211,7 @@ static bool isolate_page(struct page *page, struct list_head *pagelist)
 	bool lru = PageLRU(page);
 
 	if (PageHuge(page)) {
-		isolated = isolate_huge_page(page, pagelist);
+		isolated = !isolate_hugetlb(page, pagelist);
 	} else {
 		if (lru)
 			isolated = !isolate_lru_page(page);

mm/memory_hotplug.c

@@ -1627,7 +1627,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 
 		if (PageHuge(page)) {
 			pfn = page_to_pfn(head) + compound_nr(head) - 1;
-			isolate_huge_page(head, &source);
+			isolate_hugetlb(head, &source);
 			continue;
 		} else if (PageTransHuge(page))
 			pfn = page_to_pfn(head) + thp_nr_pages(page) - 1;

mm/mempolicy.c

@@ -607,7 +607,7 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
 	/* With MPOL_MF_MOVE, we migrate only unshared hugepage. */
 	if (flags & (MPOL_MF_MOVE_ALL) ||
 	    (flags & MPOL_MF_MOVE && page_mapcount(page) == 1)) {
-		if (!isolate_huge_page(page, qp->pagelist) &&
+		if (isolate_hugetlb(page, qp->pagelist) &&
 			(flags & MPOL_MF_STRICT))
 			/*
 			 * Failed to isolate page but allow migrating pages

mm/migrate.c

@@ -133,7 +133,7 @@ static void putback_movable_page(struct page *page)
  *
  * This function shall be used whenever the isolated pageset has been
  * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
- * and isolate_huge_page().
+ * and isolate_hugetlb().
  */
 void putback_movable_pages(struct list_head *l)
 {
@@ -1631,8 +1631,9 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
 
 	if (PageHuge(page)) {
 		if (PageHead(page)) {
-			isolate_huge_page(page, pagelist);
+			err = isolate_hugetlb(page, pagelist);
-			err = 1;
+			if (!err)
+				err = 1;
 		}
 	} else {
 		struct page *head;