linux-kernel - [PATCH v2 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page

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Date:   Wed,  6 Jan 2021 16:47:35 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     mike.kravetz@...cle.com, akpm@...ux-foundation.org
Cc:     n-horiguchi@...jp.nec.com, ak@...ux.intel.com, mhocko@...e.cz,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v2 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page

Because we only can isolate a active page via isolate_huge_page()
and hugetlbfs_fallocate() forget to mark it as active, we cannot
isolate and migrate those pages.

Only export set_page_huge_active, just leave clear_page_huge_active
as static. Because there are no external users.

Fixes: 70c3547e36f5 (hugetlbfs: add hugetlbfs_fallocate())
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 fs/hugetlbfs/inode.c    | 3 ++-
 include/linux/hugetlb.h | 2 ++
 mm/hugetlb.c            | 2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index b5c109703daa..21c20fd5f9ee 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -735,9 +735,10 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
 
 		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 
+		set_page_huge_active(page);
 		/*
 		 * unlock_page because locked by add_to_page_cache()
-		 * page_put due to reference from alloc_huge_page()
+		 * put_page() due to reference from alloc_huge_page()
 		 */
 		unlock_page(page);
 		put_page(page);
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index ebca2ef02212..b5807f23caf8 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -770,6 +770,8 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
 }
 #endif
 
+void set_page_huge_active(struct page *page);
+
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1f3bf1710b66..4741d60f8955 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1348,7 +1348,7 @@ bool page_huge_active(struct page *page)
 }
 
 /* never called for tail page */
-static void set_page_huge_active(struct page *page)
+void set_page_huge_active(struct page *page)
 {
 	VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
 	SetPagePrivate(&page[1]);
-- 
2.11.0