[PATCH 3/3] fs/proc/task_mmu: account device-private PMDs as present in smaps

[Usama Arif <usama.arif@linux.dev>]

Device-private PMDs represent mapped pages, but smaps_pmd_entry()
passes present=false to smaps_account(). That treats them like migration
entries: mapcounts are ignored, PSS is charged in full, and exclusive
mappings are accounted as shared.

Match smaps_pte_entry() and mark device-private PMDs as present so
smaps_account() uses mapcounts for PSS and private/shared accounting.

Fixes: a30b48bf1b24 ("mm/migrate_device: implement THP migration of zone device pages")
Cc: stable@vger.kernel.org
Signed-off-by: Usama Arif <usama.arif@linux.dev>
---
 fs/proc/task_mmu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index c0d391186c2b8..ad97532fc1184 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1032,8 +1032,11 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 	} else if (unlikely(thp_migration_supported())) {
 		const softleaf_t entry = softleaf_from_pmd(*pmd);
 
-		if (softleaf_has_pfn(entry))
+		if (softleaf_has_pfn(entry)) {
+			if (softleaf_is_device_private(entry))
+				present = true;
 			page = softleaf_to_page(entry);
+		}
 	}
 	if (IS_ERR_OR_NULL(page))
 		return;
-- 
2.53.0-Meta