every iput() and namei() must be inside a transaction

fs.c

@@ -314,6 +314,8 @@ iunlock(struct inode *ip)
 // be recycled.
 // If that was the last reference and the inode has no links
 // to it, free the inode (and its content) on disk.
+// All calls to iput() must be inside a transaction in
+// case it has to free the inode.
 void
 iput(struct inode *ip)
 {
@@ -601,6 +603,7 @@ skipelem(char *path, char *name)
 // Look up and return the inode for a path name.
 // If parent != 0, return the inode for the parent and copy the final
 // path element into name, which must have room for DIRSIZ bytes.
+// Must be called inside a transaction since it calls iput().
 static struct inode*
 namex(char *path, int nameiparent, char *name)
 {