1 files changed, 66 insertions, 0 deletions
diff --git a/bio.c b/bio.c
new file mode 100644
index 0000000..9be11df
--- /dev/null
+++ b/bio.c
@@ -0,0 +1,66 @@
+#include "types.h"
+#include "param.h"
+#include "x86.h"
+#include "mmu.h"
+#include "proc.h"
+#include "defs.h"
+#include "spinlock.h"
+#include "buf.h"
+
+struct buf buf[NBUF];
+struct spinlock buf_table_lock;
+
+struct buf *
+getblk()
+{
+  int i;
+
+  acquire(&buf_table_lock);
+
+  // XXX need to lock the block even if not caching, to
+  // avoid read modify write problems.
+
+  while(1){
+    for(i = 0; i < NBUF; i++){
+      if((buf[i].flags & B_BUSY) == 0){
+        buf[i].flags |= B_BUSY;
+        release(&buf_table_lock);
+        return buf + i;
+      }
+    }
+    sleep(buf, &buf_table_lock);
+  }
+}
+
+struct buf *
+bread(uint dev, uint sector)
+{
+  void *c;
+  struct buf *b;
+  extern struct spinlock ide_lock;
+
+  b = getblk();
+
+  acquire(&ide_lock);
+  c = ide_start_read(dev & 0xff, sector, b->data, 1);
+  // sleep (c, &ide_lock);
+  ide_finish_read(c);
+  release(&ide_lock);
+
+  return b;
+}
+
+void
+brelse(struct buf *b)
+{
+  if((b->flags & B_BUSY) == 0)
+    panic("brelse");
+  
+  acquire(&buf_table_lock);
+
+  b->flags &= ~B_BUSY;
+  wakeup(buf);
+
+  release(&buf_table_lock);
+}
+