[PATCH v6 8/8] mm/shmem, swap: fix major fault counting

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

If the swapin failed, don't update the major fault count.  There is a long
existing comment for doing it this way, now with previous cleanups, we can
finally fix it.

Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/shmem.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index aed5da693855..41eb4aa60be5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2356,13 +2356,6 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 	/* Look it up and read it in.. */
 	folio = swap_cache_get_folio(swap, NULL, 0);
 	if (!folio) {
-		/* Or update major stats only when swapin succeeds?? */
-		if (fault_type) {
-			*fault_type |= VM_FAULT_MAJOR;
-			count_vm_event(PGMAJFAULT);
-			count_memcg_event_mm(fault_mm, PGMAJFAULT);
-		}
-
 		if (data_race(si->flags & SWP_SYNCHRONOUS_IO)) {
 			/* Direct swapin skipping swap cache & readahead */
 			folio = shmem_swap_alloc_folio(inode, vma, index,
@@ -2381,6 +2374,11 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 				goto failed;
 			}
 		}
+		if (fault_type) {
+			*fault_type |= VM_FAULT_MAJOR;
+			count_vm_event(PGMAJFAULT);
+			count_memcg_event_mm(fault_mm, PGMAJFAULT);
+		}
 	}
 
 	if (order > folio_order(folio)) {
-- 
2.50.1