Rm spin::Mutex except for easy-fs & add new test huge_write & flush cache to disk after a write transaction

os/src/sbi.rs

@@ -14,11 +14,12 @@ const SBI_SHUTDOWN: usize = 8;
 fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
     let mut ret;
     unsafe {
-        llvm_asm!("ecall"
-            : "={x10}" (ret)
-            : "{x10}" (arg0), "{x11}" (arg1), "{x12}" (arg2), "{x17}" (which)
-            : "memory"
-            : "volatile"
+        asm!(
+            "ecall",
+            inlateout("x10") arg0 => ret,
+            in("x11") arg1,
+            in("x12") arg2,
+            in("x17") which,
         );
     }
     ret