x

1 files changed, 26 insertions, 0 deletions

diff --git a/kernel/virtio_disk.c b/kernel/virtio_disk.c
index ae6c164..dfca2bc 100644
--- a/kernel/virtio_disk.c
+++ b/kernel/virtio_disk.c
@@ -212,6 +212,28 @@ alloc3_desc(int *idx)
   return 0;
 }
 
+#ifdef LAB_LOCK
+//
+// check that there are at most NBUF distinct
+// struct buf's, which the lock lab requires.
+//
+static struct buf *xbufs[NBUF];
+static void
+checkbuf(struct buf *b)
+{
+  for(int i = 0; i < NBUF; i++){
+    if(xbufs[i] == b){
+      return;
+    }
+    if(xbufs[i] == 0){
+      xbufs[i] = b;
+      return;
+    }
+  }
+  panic("more than NBUF bufs");
+}
+#endif
+
 void
 virtio_disk_rw(struct buf *b, int write)
 {
@@ -219,6 +241,10 @@ virtio_disk_rw(struct buf *b, int write)
 
   acquire(&disk.vdisk_lock);
 
+#ifdef LAB_LOCK
+  checkbuf(b);
+#endif
+
   // the spec's Section 5.2 says that legacy block operations use
   // three descriptors: one for type/reserved/sector, one for the
   // data, one for a 1-byte status result.