Acquire inode ref before checking if inode is valid

b1445295 · Silas Boyd-Wickizer · b2e88e79 · b1445295
--- a/kernel/fs.cc
+++ b/kernel/fs.cc
@@ -189,6 +189,7 @@ ialloc(u32 dev, short type)
      // maybe this inode is free. look at it via the
      // inode cache to make sure.
      struct inode *ip = iget(dev, inum);
+      assert(ip->valid());
      ilock(ip, 1);
      if(ip->type == 0){
        ip->type = type;
@@ -263,15 +264,15 @@ iget(u32 dev, u32 inum)
    scoped_gc_epoch e;
    struct inode *ip = ins->lookup(make_pair(dev, inum));
    if (ip) {
-      if (!(ip->flags & I_VALID)) {
+      if (ip->tryinc()) {
-        acquire(&ip->lock);
+        if (!(ip->flags & I_VALID)) {
-        while((ip->flags & I_VALID) == 0)
+          acquire(&ip->lock);
-	  cv_sleep(&ip->cv, &ip->lock);
+          while((ip->flags & I_VALID) == 0)
-        release(&ip->lock);
+            cv_sleep(&ip->cv, &ip->lock);
-      }
+          release(&ip->lock);
+        }
-      if (ip->tryinc())
        return ip;
+      }
    }
  }