linux-kernel - [PATCH 4.9 34/43] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page

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Message-Id: <20210208145807.694524853@linuxfoundation.org>
Date:   Mon,  8 Feb 2021 16:01:00 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Muchun Song <songmuchun@...edance.com>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 34/43] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page

From: Muchun Song <songmuchun@...edance.com>

commit 585fc0d2871c9318c949fbf45b1f081edd489e96 upstream.

If a new hugetlb page is allocated during fallocate it will not be
marked as active (set_page_huge_active) which will result in a later
isolate_huge_page failure when the page migration code would like to
move that page.  Such a failure would be unexpected and wrong.

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

Link: https://lkml.kernel.org/r/20210115124942.46403-3-songmuchun@bytedance.com
Fixes: 70c3547e36f5 (hugetlbfs: add hugetlbfs_fallocate())
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Cc: David Hildenbrand <david@...hat.com>
Cc: Yang Shi <shy828301@...il.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/hugetlbfs/inode.c    |    3 ++-
 include/linux/hugetlb.h |    3 +++
 mm/hugetlb.c            |    2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -665,8 +665,9 @@ static long hugetlbfs_fallocate(struct f
 
 		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
 
+		set_page_huge_active(page);
 		/*
-		 * page_put due to reference from alloc_huge_page()
+		 * put_page() due to reference from alloc_huge_page()
 		 * unlock_page because locked by add_to_page_cache()
 		 */
 		put_page(page);
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -502,6 +502,9 @@ static inline void hugetlb_count_sub(lon
 {
 	atomic_long_sub(l, &mm->hugetlb_usage);
 }
+
+void set_page_huge_active(struct page *page);
+
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 #define alloc_huge_page(v, a, r) NULL
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1215,7 +1215,7 @@ 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]);