[PATCH v3 6/7] mm/shmem, swap: fix major fault counting

[Kairui Song]

From: Kairui Song <kasong@xxxxxxxxxxx>

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@xxxxxxxxxxx>
---
 mm/shmem.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 5f2641fd1be7..ea9a105ded5d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2316,12 +2316,6 @@ 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 mTHP swapin without swap cache or readahead */
 			folio = shmem_swapin_direct(inode, vma, index,
@@ -2341,6 +2335,11 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 		}
 		if (!folio)
 			goto failed;
+		if (fault_type) {
+			*fault_type |= VM_FAULT_MAJOR;
+			count_vm_event(PGMAJFAULT);
+			count_memcg_event_mm(fault_mm, PGMAJFAULT);
+		}
 	}
 	/*
 	 * We need to split an existing large entry if swapin brought in a
-- 
2.50.0