splice: fsnotify_access(in), fsnotify_modify(out) on success in tee

Same logic applies here: this can fill up the pipe, and pollers that rely
on getting IN_MODIFY notifications never wake up.

Fixes: 983652c691 ("splice: report related fsnotify events")
Link: https://lore.kernel.org/linux-fsdevel/jbyihkyk5dtaohdwjyivambb2gffyjs3dodpofafnkkunxq7bu@jngkdxx65pux/t/#u
Link: https://bugs.debian.org/1039488
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Acked-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <10d76dd8c85017ae3cd047c9b9a32e26daefdaa2.1688393619.git.nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/splice.c

@@ -1929,6 +1929,11 @@ long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
 		}
 	}
 
+	if (ret > 0) {
+		fsnotify_access(in);
+		fsnotify_modify(out);
+	}
+
 	return ret;
 }