userswap: fix BUG_ON in __mcopy_atomic()

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6CAIM

--------------------------------

When the swap-in buffer contains no physical pages, the errno in
mfill_atomic_pte_nocopy() will be ENOENT. A BUG_ON error will occur
because the userswap feature does not use the struct page *page and page
is set to NULL.
To fix this issue, the errno should be changed from ENOENT to EINVAL.
Signed-off-by: NZhangPeng <zhangpeng362@huawei.com>

mm/userswap.c

@@ -407,7 +407,7 @@ int mfill_atomic_pte_nocopy(struct mm_struct *mm,
 
 	src_vma = find_vma(mm, src_addr);
 	if (!src_vma || src_addr < src_vma->vm_start)
-		return -ENOENT;
+		return -EINVAL;
 
 	if (src_vma->vm_flags & VM_LOCKED)
 		return -EINVAL;