[PATCH] mm/huge_memory: skip huge_zero_pmd in zap_huge_pmd_folio()

[Bibo Mao]

when executing command "make check" with qemu software, there is
error report like this:
 BUG: Bad rss-counter state mm:00000000972846bc type:MM_FILEPAGES val:-4096 Comm:bios-tables-tes Pid:27802
 BUG: Bad rss-counter state mm:00000000752180c5 type:MM_FILEPAGES val:-2048 Comm:worker Pid:27815
 BUG: Bad rss-counter state mm:000000009c2f6a61 type:MM_FILEPAGES val:-2048 Comm:qom-test Pid:27825

The problem is that when application exits, rss counter is calculated
with huge_zero_pmd huge page, instead it should be skipped.

Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
 mm/huge_memory.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 970e077019b7..3cbea344d4a2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2423,6 +2423,9 @@ static void zap_huge_pmd_folio(struct mm_struct *mm, struct vm_area_struct *vma,
 {
 	const bool is_device_private = folio_is_device_private(folio);
 
+	if (is_huge_zero_pmd(pmdval))
+		return;
+
 	/* Present and device private folios are rmappable. */
 	if (is_present || is_device_private)
 		folio_remove_rmap_pmd(folio, &folio->page, vma);

base-commit: 3b3bea6d4b9c162f9e555905d96b8c1da67ecd5b
-- 
2.39.3