From: Balbir Singh <balbirs@nvidia.com>
Date: Wed, 19 Feb 2025 23:13:37 +0000 (+1100)
Subject: mm/migrate_device: do not access pgmap for non zone device pages
X-Git-Tag: next-20250224~159^2~91
X-Git-Url: https://gentwo.org/gitweb/?a=commitdiff_plain;h=21e96315c2e47047226a422a2caf963b64ccf103;p=linux%2F.git

mm/migrate_device: do not access pgmap for non zone device pages

page_pgmap() is referenced before checking if the page is a zone device
page and this triggers the warning in page_pgmap().  Refactor the code to
use the helper function after relevant checks.

Link: https://lkml.kernel.org/r/20250219231337.364133-1-balbirs@nvidia.com
Signed-off-by: Balbir Singh <balbirs@nvidia.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 6771893d4601..e0bf771edb6f 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -153,14 +153,17 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				goto next;
 			}
 			page = vm_normal_page(migrate->vma, addr, pte);
-			pgmap = page_pgmap(page);
 			if (page && !is_zone_device_page(page) &&
 			    !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
 				goto next;
-			else if (page && is_device_coherent_page(page) &&
-			    (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
-			     pgmap->owner != migrate->pgmap_owner))
-				goto next;
+			else if (page && is_device_coherent_page(page)) {
+				pgmap = page_pgmap(page);
+
+				if (!(migrate->flags &
+					MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
+					pgmap->owner != migrate->pgmap_owner)
+					goto next;
+			}
 			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
 			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
 		}