create doesn't touch parent director references

b75f12ac · Silas Boyd-Wickizer · 7fe2e84a · b75f12ac · b75f12ac · b75f12ac
--- a/include/kernel.hh
+++ b/include/kernel.hh
@@ -89,6 +89,7 @@ struct inode*   dirlookup(struct inode*, char*);
 struct inode*   ialloc(u32, short);
 struct inode*   namei(inode *cwd, const char*);
 void            iput(struct inode*);
+void            iput(inode* ip, bool haveref);
 struct inode*   iget(u32 dev, u32 inum);
 void            ilock(struct inode*, int writer);
 void            iunlockput(struct inode*);

--- a/kernel/fs.cc
+++ b/kernel/fs.cc
@@ -476,6 +476,13 @@ iunlock(struct inode *ip)
  release(&ip->lock);
 }
+void
+iput(inode* ip, bool haveref)
+{
+  if (haveref)
+    iput(ip);
+}
 // Caller holds reference to unlocked ip.  Drop reference.
 void
 iput(struct inode *ip)

--- a/kernel/sysfile.cc
+++ b/kernel/sysfile.cc
@@ -224,18 +224,23 @@ create(inode *cwd, const char *path, short type, short major, short minor)
 {
  struct inode *ip, *dp;
  char name[DIRSIZ];
+  bool haveref = false;
  mt_ascope ascope("%s(%d.%d,%s,%d,%d,%d)",
                   __func__, cwd->dev, cwd->inum,
                   path, type, major, minor);
 retry:
-  if((dp = nameiparent(cwd, path, name)) == 0)
+  {
+    scoped_gc_epoch e;
+    if((dp = __nameiparent(cwd, path, name, &haveref)) == 0)
      return 0;
    if(dp->type != T_DIR)
      panic("create");
    if((ip = dirlookup(dp, name)) != 0){
-    iput(dp);
+      iput(dp, haveref);
      ilock(ip, 1);
      if(type == T_FILE && ip->type == T_FILE)
        return ip;
@@ -265,12 +270,19 @@ create(inode *cwd, const char *path, short type, short major, short minor)
      // create race
      ip->unlink();
      iunlockput(ip);
-    iput(dp);
+      iput(dp, haveref);
      goto retry;
    }
+    if (!dp->valid()) {
+      // XXX(sbw) we need to undo everything we just did
+      // (at least all the modifications to dp) and retry.
+      panic("create: race");
+    }
+  }
  //nc_insert(dp, name, ip);
-  iput(dp);
+  iput(dp, haveref);
  return ip;
 }