From: Alistair Popple <apopple@nvidia.com>

Date: Mon, 14 Nov 2022 22:55:37 +1100

Subject: mm/memory: return vm_fault_t result from migrate_to_ram() callback

Git-commit: 4a955bed882e734807024afd8f53213d4c61ff97

Patch-mainline: v6.1-rc7

References: jsc#PED-1294

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.

Link: https://lkml.kernel.org/r/20221114115537.727371-1-apopple@nvidia.com

Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device private page")

Signed-off-by: Alistair Popple <apopple@nvidia.com>

Acked-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.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: Lyude Paul <lyude@redhat.com>

Cc: Jason Gunthorpe <jgg@nvidia.com>

Cc: Michael Ellerman <mpe@ellerman.id.au>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

---

 mm/memory.c |    2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/memory.c

+++ b/mm/memory.c

@@ -3513,7 +3513,7 @@ vm_fault_t do_swap_page(struct vm_fault

 			 */

 			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;