fix iget() bug that allocated in-use inode[] entries

Notes

@@ -357,7 +357,6 @@ OH! recursive interrupts will use up any amount of cpu[].stack!
 
 disk scheduling
 mkdir
-more than one directory content block
 sh arguments
 sh redirection
 indirect blocks
@@ -366,17 +365,10 @@ two bugs in unlink: don't just return if nlink > 0,
 is there a create/create race for same file name?
   resulting in two entries w/ same name in directory?
 
-namei
-  return just inode
-  return offset in dir where found, w/ dir locked, for unlink
-  return dir locked, for mknod
-
-is the offset alone useful? how do I read/write it?
-
 test: one process unlinks a file while another links to it
 test: simultaneous create of same file
 test: one process opens a file while another deletes it
 
-oy, mkfs wants dir size to be last written entry, but i
-  want it to be nblocks*512
-  maybe fix kernel code to handle former
+wdir should use writei, to avoid special-case block allocation
+  also readi
+  is dir locked? probably