[PATCH] Revert "mm: migration: fix the FOLL_GET failure on following huge page"

[PATCH] Revert "mm: migration: fix the FOLL_GET failure on following huge page"

[Baolin Wang]

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@linux.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

RE: [PATCH] Revert "mm: migration: fix the FOLL_GET failure on following huge page"

[Wang, Haiyue]

> -----Original Message-----
> From: Baolin Wang <baolin.wang@linux.alibaba.com>
> Sent: Wednesday, November 9, 2022 16:40
> To: akpm@linux-foundation.org
> Cc: Wang, Haiyue <haiyue.wang@intel.com>; Huang, Ying <ying.huang@intel.com>; mike.kravetz@oracle.com;
> songmuchun@bytedance.com; baolin.wang@linux.alibaba.com; linux-mm@kvack.org; linux-
> kernel@vger.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@linux.alibaba.com>
> ---

Cool, thanks, my ugly code is gone. ;-)

Acked-by: Haiyue Wang <haiyue.wang@intel.com>

>  mm/migrate.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> --
> 1.8.3.1