mm: fix the handling Non-LRU pages returned by follow_page

The handling Non-LRU pages returned by follow_page() jumps directly, it
doesn't call put_page() to handle the reference count, since 'FOLL_GET'
flag for follow_page() has get_page() called.  Fix the zone device page
check by handling the page reference count correctly before returning.

And as David reviewed, "device pages are never PageKsm pages".  Drop this
zone device page check for break_ksm().

Since the zone device page can't be a transparent huge page, so drop the
redundant zone device page check for split_huge_pages_pid().  (by Miaohe)

Link: https://lkml.kernel.org/r/20220823135841.934465-3-haiyue.wang@intel.com
Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 533ede86b4b9..1fafd531f669 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
 		cond_resched();
 		page = follow_page(vma, addr,
 				FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
-		if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
+		if (IS_ERR_OR_NULL(page))
 			break;
 		if (PageKsm(page))
 			ret = handle_mm_fault(vma, addr,
@@ -560,12 +560,15 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
 		goto out;
 
 	page = follow_page(vma, addr, FOLL_GET);
-	if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
+	if (IS_ERR_OR_NULL(page))
 		goto out;
+	if (is_zone_device_page(page))
+		goto out_putpage;
 	if (PageAnon(page)) {
 		flush_anon_page(vma, page, addr);
 		flush_dcache_page(page);
 	} else {
+out_putpage:
 		put_page(page);
 out:
 		page = NULL;
@@ -2322,11 +2325,13 @@ next_mm:
 			if (ksm_test_exit(mm))
 				break;
 			*page = follow_page(vma, ksm_scan.address, FOLL_GET);
-			if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) {
+			if (IS_ERR_OR_NULL(*page)) {
 				ksm_scan.address += PAGE_SIZE;
 				cond_resched();
 				continue;
 			}
+			if (is_zone_device_page(*page))
+				goto next_page;
 			if (PageAnon(*page)) {
 				flush_anon_page(vma, *page, ksm_scan.address);
 				flush_dcache_page(*page);
@@ -2341,6 +2346,7 @@ next_mm:
 				mmap_read_unlock(mm);
 				return rmap_item;
 			}
+next_page:
 			put_page(*page);
 			ksm_scan.address += PAGE_SIZE;
 			cond_resched();