[PATCH rfc 7/9] fs: hugetlbfs: support poison recover from hugetlbfs_migrate_folio()

[Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>]

This is similar to __migrate_folio(), use folio_mc_copy() to avoid
panic when copy poisoned folio.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 fs/hugetlbfs/inode.c    | 10 +++++++++-
 include/linux/migrate.h |  1 +
 mm/migrate.c            |  3 +--
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 52839ffdd9a1..3871968d1780 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1119,6 +1119,14 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping,
 {
 	int rc;
 
+	/* Check whether src does not have extra refs before we do more work */
+	if (folio_ref_count(src) != folio_expected_refs(mapping, src))
+		return -EAGAIN;
+
+	rc = folio_mc_copy(dst, src);
+	if (rc)
+		return rc;
+
 	rc = migrate_huge_page_move_mapping(mapping, dst, src);
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
@@ -1129,7 +1137,7 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping,
 		hugetlb_set_folio_subpool(src, NULL);
 	}
 
-	folio_migrate_copy(dst, src);
+	folio_migrate_flags(dst, src);
 
 	return MIGRATEPAGE_SUCCESS;
 }
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 517f70b70620..ab387ea66365 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -79,6 +79,7 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
 void folio_migrate_copy(struct folio *newfolio, struct folio *folio);
 int folio_migrate_mapping(struct address_space *mapping,
 		struct folio *newfolio, struct folio *folio, int extra_count);
+int folio_expected_refs(struct address_space *mapping, struct folio *folio);
 
 #else
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 99286394b5e5..097d67c82f8b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -375,8 +375,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 }
 #endif
 
-static int folio_expected_refs(struct address_space *mapping,
-		struct folio *folio)
+int folio_expected_refs(struct address_space *mapping, struct folio *folio)
 {
 	int refs = 1;
 	if (!mapping)
-- 
2.27.0