[PATCH] mm/memory: Return vm_fault_t result from migrate_to_ram() callback

[Alistair Popple <apopple@nvidia.com>]

The migrate_to_ram() callback should always succeed, but in rare cases
can fail usually returning VM_FAULT_SIGBUS. Commit 16ce101db85d
("mm/memory.c: fix race when faulting a device private page")
incorrectly stopped passing the return code up the stack. Fix this by
setting the ret variable, restoring the previous behaviour on
migrate_to_ram() failure.

Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device private page")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>

---

Hi Andrew, I noticed my series needs another small fix which I'm
hoping you can apply for v6.1-rcX. Thanks (and sorry for not catching
this sooner).
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index f88c351aecd4..8a6d5c823f91 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3763,7 +3763,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			 */
 			get_page(vmf->page);
 			pte_unmap_unlock(vmf->pte, vmf->ptl);
-			vmf->page->pgmap->ops->migrate_to_ram(vmf);
+			ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
 			put_page(vmf->page);
 		} else if (is_hwpoison_entry(entry)) {
 			ret = VM_FAULT_HWPOISON;
-- 
2.35.1