pass a struct path to vfs_statfs

We'll need the path to implement the flags field for statvfs support.
We do have it available in all callers except:

 - ecryptfs_statfs.  This one doesn't actually need vfs_statfs but just
   needs to do a caller to the lower filesystem statfs method.
 - sys_ustat.  Add a non-exported statfs_by_dentry helper for it which
   doesn't won't be able to fill out the flags field later on.

In addition rename the helpers for statfs vs fstatfs to do_*statfs instead
of the misleading vfs prefix.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/compat.c b/fs/compat.c
index 6490d21..fc6c2ad 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -266,7 +266,7 @@
 	error = user_path(pathname, &path);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(path.dentry, &tmp);
+		error = vfs_statfs(&path, &tmp);
 		if (!error)
 			error = put_compat_statfs(buf, &tmp);
 		path_put(&path);
@@ -284,7 +284,7 @@
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_path.dentry, &tmp);
+	error = vfs_statfs(&file->f_path, &tmp);
 	if (!error)
 		error = put_compat_statfs(buf, &tmp);
 	fput(file);
@@ -334,7 +334,7 @@
 	error = user_path(pathname, &path);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(path.dentry, &tmp);
+		error = vfs_statfs(&path, &tmp);
 		if (!error)
 			error = put_compat_statfs64(buf, &tmp);
 		path_put(&path);
@@ -355,7 +355,7 @@
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_path.dentry, &tmp);
+	error = vfs_statfs(&file->f_path, &tmp);
 	if (!error)
 		error = put_compat_statfs64(buf, &tmp);
 	fput(file);
@@ -378,7 +378,7 @@
 	sb = user_get_super(new_decode_dev(dev));
 	if (!sb)
 		return -EINVAL;
-	err = vfs_statfs(sb->s_root, &sbuf);
+	err = statfs_by_dentry(sb->s_root, &sbuf);
 	drop_super(sb);
 	if (err)
 		return err;