Kernel test robot, reported a sparse error with the patch

The sparse report states:

>> drivers/gpu/drm/nouveau/nouveau_dmem.c:259:13: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted vm_fault_t [assigned] [usertype] ret @@     got int @@
   drivers/gpu/drm/nouveau/nouveau_dmem.c:259:13: sparse:     expected restricted vm_fault_t [assigned] [usertype] ret
   drivers/gpu/drm/nouveau/nouveau_dmem.c:259:13: sparse:     got int

ret of type vm_fault_t is reused to capture the return value of
nouveau_dmem_copy_folio(), which returns an int. Use a new variable
err (of type int) to get the return value from the function to fix
the reported issue.

The reported issue is not new, prior to this, the function called
nouveau_dmem_copy_folio() was called nouveau_dmem_copy_one() and
ret was used to capture it's return value.

The reported issue also does not cause any runtime errors. The
return value from the function is used as a boolean value, to check if
nouveau_dmem_copy_folio() succeeded or failed.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511121922.oP20Lzb8-lkp@intel.com/

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mika Penttilä <mpenttil@redhat.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Francois Dugast <francois.dugast@intel.com>

Signed-off-by: Balbir Singh <balbirs@nvidia.com>
---
This fixup should be squashed into the patch "gpu/drm/nouveau: enable
THP support for GPU memory" of mm/mm-unstable
David wanted me to change the patch prefix to drm/nouveau/dmem, I can
resend the patches, fixup and this one (squashed) if needed.

 drivers/gpu/drm/nouveau/nouveau_dmem.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 244812e7dd69..58071652679d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -188,6 +188,7 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm_fault *vmf)
 	struct nouveau_svmm *svmm;
 	struct page *dpage;
 	vm_fault_t ret = 0;
+	int err;
 	struct migrate_vma args = {
 		.vma		= vmf->vma,
 		.pgmap_owner	= drm->dev,
@@ -256,9 +257,9 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm_fault *vmf)
 	svmm = folio_zone_device_data(sfolio);
 	mutex_lock(&svmm->mutex);
 	nouveau_svmm_invalidate(svmm, args.start, args.end);
-	ret = nouveau_dmem_copy_folio(drm, sfolio, dfolio, &dma_info);
+	err = nouveau_dmem_copy_folio(drm, sfolio, dfolio, &dma_info);
 	mutex_unlock(&svmm->mutex);
-	if (ret) {
+	if (err) {
 		ret = VM_FAULT_SIGBUS;
 		goto done;
 	}
-- 
2.51.1