vfio/type1: Change success value of vaddr_get_pfn()

vaddr_get_pfn() simply returns 0 on success.  Have it report the number
of pfns successfully gotten instead, whether from page pinning or
follow_fault_pfn(), which will be used later when batching pinning.

Change the last check in vfio_pin_pages_remote() for consistency with
the other two.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -495,6 +495,10 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 	return ret;
 }
 
+/*
+ * Returns the positive number of pfns successfully obtained or a negative
+ * error code.
+ */
 static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 			 int prot, unsigned long *pfn)
 {
@@ -511,7 +515,6 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 				    page, NULL, NULL);
 	if (ret == 1) {
 		*pfn = page_to_pfn(page[0]);
-		ret = 0;
 		goto done;
 	}
 
@@ -525,8 +528,12 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 		if (ret == -EAGAIN)
 			goto retry;
 
-		if (!ret && !is_invalid_reserved_pfn(*pfn))
-			ret = -EFAULT;
+		if (!ret) {
+			if (is_invalid_reserved_pfn(*pfn))
+				ret = 1;
+			else
+				ret = -EFAULT;
+		}
 	}
 done:
 	mmap_read_unlock(mm);
@@ -607,7 +614,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
 		return -ENODEV;
 
 	ret = vaddr_get_pfn(current->mm, vaddr, dma->prot, pfn_base);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	pinned++;
@@ -634,7 +641,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
 	for (vaddr += PAGE_SIZE, iova += PAGE_SIZE; pinned < npage;
 	     pinned++, vaddr += PAGE_SIZE, iova += PAGE_SIZE) {
 		ret = vaddr_get_pfn(current->mm, vaddr, dma->prot, &pfn);
-		if (ret)
+		if (ret < 0)
 			break;
 
 		if (pfn != *pfn_base + pinned ||
@@ -660,7 +667,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
 	ret = vfio_lock_acct(dma, lock_acct, false);
 
 unpin_out:
-	if (ret) {
+	if (ret < 0) {
 		if (!rsvd) {
 			for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
 				put_pfn(pfn, dma->prot);
@@ -704,7 +711,7 @@ static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
 		return -ENODEV;
 
 	ret = vaddr_get_pfn(mm, vaddr, dma->prot, pfn_base);
-	if (!ret && do_accounting && !is_invalid_reserved_pfn(*pfn_base)) {
+	if (ret == 1 && do_accounting && !is_invalid_reserved_pfn(*pfn_base)) {
 		ret = vfio_lock_acct(dma, 1, true);
 		if (ret) {
 			put_pfn(*pfn_base, dma->prot);