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From:   Miaohe Lin <linmiaohe@huawei.com>
To:     <akpm@linux-foundation.org>, <mike.kravetz@oracle.com>,
        <naoya.horiguchi@nec.com>
CC:     <peterx@redhat.com>, <apopple@nvidia.com>, <ying.huang@intel.com>,
        <david@redhat.com>, <songmuchun@bytedance.com>, <hch@lst.de>,
        <dhowells@redhat.com>, <cl@linux.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, <linmiaohe@huawei.com>
Subject: [PATCH v3 3/4] mm/migration: return errno when isolate_huge_page failed
Date:   Wed, 25 May 2022 16:18:21 +0800
Message-ID: <20220525081822.53547-4-linmiaohe@huawei.com>
In-Reply-To: <20220525081822.53547-1-linmiaohe@huawei.com>
References: <20220525081822.53547-1-linmiaohe@huawei.com>
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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.

Fixes: e8db67eb0ded ("mm: migrate: move_pages() supports thp migration")
Suggested-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 include/linux/hugetlb.h |  6 +++---
 mm/gup.c                |  2 +-
 mm/hugetlb.c            | 11 +++++------
 mm/memory-failure.c     |  2 +-
 mm/mempolicy.c          |  2 +-
 mm/migrate.c            |  5 +++--
 6 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index e4cff27d1198..756b66ff025e 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -170,7 +170,7 @@ 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);
@@ -376,9 +376,9 @@ 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)
diff --git a/mm/gup.c b/mm/gup.c
index 551264407624..3899dcb288a6 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1898,7 +1898,7 @@ 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;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 01f0e2e5ab48..2026fcfc8886 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2765,8 +2765,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
 		 * Fail with -EBUSY if not possible.
 		 */
 		spin_unlock_irq(&hugetlb_lock);
-		if (!isolate_huge_page(old_page, list))
-			ret = -EBUSY;
+		ret = isolate_hugetlb(old_page, list);
 		spin_lock_irq(&hugetlb_lock);
 		goto free_new;
 	} else if (!HPageFreed(old_page)) {
@@ -2842,7 +2841,7 @@ 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);
@@ -6945,15 +6944,15 @@ 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);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b85661cbdc4a..5deb1b1cb2fd 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2166,7 +2166,7 @@ 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);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 2dad094177bf..f96d55131689 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -602,7 +602,7 @@ 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
diff --git a/mm/migrate.c b/mm/migrate.c
index 337336115e43..97c31b87d1a2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1627,8 +1627,9 @@ 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 = 1;
+			err = isolate_hugetlb(page, pagelist);
+			if (!err)
+				err = 1;
 		}
 	} else {
 		struct page *head;
-- 
2.23.0