mm: handle write faults to RO pages under the VMA lock

I think this is a pretty rare occurrence, but for consistency handle
faults with the VMA lock held the same way that we handle other faults
with the VMA lock held.

Link: https://lkml.kernel.org/r/20231006195318.4087158-7-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory.c

@@ -3301,10 +3301,9 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
 		vm_fault_t ret;
 
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
-		if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
-			vma_end_read(vmf->vma);
-			return VM_FAULT_RETRY;
-		}
+		ret = vmf_can_call_fault(vmf);
+		if (ret)
+			return ret;
 
 		vmf->flags |= FAULT_FLAG_MKWRITE;
 		ret = vma->vm_ops->pfn_mkwrite(vmf);
@@ -3328,10 +3327,10 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf, struct folio *folio)
 		vm_fault_t tmp;
 
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
-		if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+		tmp = vmf_can_call_fault(vmf);
+		if (tmp) {
 			folio_put(folio);
-			vma_end_read(vmf->vma);
-			return VM_FAULT_RETRY;
+			return tmp;
 		}
 
 		tmp = do_page_mkwrite(vmf, folio);