[PATCH] vfs: return EINVAL instead of ENOENT when missing source

[Murphy Zhou <jencce.kernel@xxxxxxxxx>]

mount(2) with a NULL source device would return ENOENT instead of EINVAL
after this commit:

commit f3a09c92018a91ad0981146a4ac59414f814d801
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date:   Sun Dec 23 18:55:56 2018 -0500

    introduce fs_context methods

Change the return value to be compatible with the old behaviour.

This was caught by LTP mount02[1]. This testcase is calling mount(2) with a
NULL device name and expecting EINVAL to PASS but now we are getting ENOENT.

[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/mount/mount02.c

Signed-off-by: Murphy Zhou <jencce.kernel@xxxxxxxxx>
---
 fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index 583a0124bc39..48e51f13a4ba 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1469,7 +1469,7 @@ int vfs_get_tree(struct fs_context *fc)
 
 	if (fc->fs_type->fs_flags & FS_REQUIRES_DEV && !fc->source) {
 		errorf(fc, "Filesystem requires source device");
-		return -ENOENT;
+		return -EINVAL;
 	}
 
 	if (fc->root)
-- 
2.21.0