mm: migration: fix the FOLL_GET failure on following huge page

Not all huge page APIs support FOLL_GET option, so the __NR_move_pages
will fail to get the page node information for huge page.

This is an temporary solution to mitigate the racing fix.

After supporting follow huge page by FOLL_GET is done, this fix can be
reverted safely.

Link: https://lkml.kernel.org/r/20220812084921.409142-1-haiyue.wang@intel.com
Fixes: 4cd614841c06 ("mm: migration: fix possible do_pages_stat_array racing with memory offline")
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index 0433a71d2bee41b8a976919282f525901714e870..8bea00ee045fc2d2f250e1ee2d3cd477e52c23c0 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1852,6 +1852,7 @@ 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;
@@ -1860,8 +1861,12 @@ 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_GET | FOLL_DUMP);
+               page = follow_page(vma, addr, foll_flags);
 
                err = PTR_ERR(page);
                if (IS_ERR(page))
@@ -1869,7 +1874,8 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
 
                if (page && !is_zone_device_page(page)) {
                        err = page_to_nid(page);
-                       put_page(page);
+                       if (foll_flags & FOLL_GET)
+                               put_page(page);
                } else {
                        err = -ENOENT;
                }