linux-kernel - [PATCH] Revert "mm: migration: fix the FOLL

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Date:   Wed,  9 Nov 2022 16:40:27 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     akpm@...ux-foundation.org
Cc:     haiyue.wang@...el.com, ying.huang@...el.com,
        mike.kravetz@...cle.com, songmuchun@...edance.com,
        baolin.wang@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "mm: migration: fix the FOLL_GET failure on following huge page"

Revert commit 831568214883 ("mm: migration: fix the FOLL_GET failure on
following huge page"), since after commit 1a6baaa0db73 ("s390/hugetlb:
switch to generic version of follow_huge_pud()") and commit 57a196a58421
("hugetlb: simplify hugetlb handling in follow_page_mask") were merged,
now all the following huge page routines can support FOLL_GET operation.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 mm/migrate.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 1317e5c..53af072 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1908,7 +1908,6 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
 
 	for (i = 0; i < nr_pages; i++) {
 		unsigned long addr = (unsigned long)(*pages);
-		unsigned int foll_flags = FOLL_DUMP;
 		struct vm_area_struct *vma;
 		struct page *page;
 		int err = -EFAULT;
@@ -1917,12 +1916,8 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
 		if (!vma)
 			goto set_status;
 
-		/* Not all huge page follow APIs support 'FOLL_GET' */
-		if (!is_vm_hugetlb_page(vma))
-			foll_flags |= FOLL_GET;
-
 		/* FOLL_DUMP to ignore special (like zero) pages */
-		page = follow_page(vma, addr, foll_flags);
+		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
 
 		err = PTR_ERR(page);
 		if (IS_ERR(page))
@@ -1935,8 +1930,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
 		if (!is_zone_device_page(page))
 			err = page_to_nid(page);
 
-		if (foll_flags & FOLL_GET)
-			put_page(page);
+		put_page(page);
 set_status:
 		*status = err;
 
-- 
1.8.3.1