+ mm-allow-compound-zone-device-pages-fix.patch added to mm-unstable branch

+ mm-allow-compound-zone-device-pages-fix.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/migrate_device: do not access pgmap for non zone device pages
has been added to the -mm mm-unstable branch.  Its filename is
     mm-allow-compound-zone-device-pages-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-allow-compound-zone-device-pages-fix.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Balbir Singh <balbirs@nvidia.com>
Subject: mm/migrate_device: do not access pgmap for non zone device pages
Date: Thu, 20 Feb 2025 10:13:37 +1100

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>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate_device.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/mm/migrate_device.c~mm-allow-compound-zone-device-pages-fix
+++ a/mm/migrate_device.c
@@ -153,14 +153,17 @@ again:
 				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;
 		}
_

Patches currently in -mm which might be from balbirs@nvidia.com are

mm-allow-compound-zone-device-pages-fix.patch