kernel - Do not allow destroyed namecache entries to be re-resolved

* Do not allow a destroyed namecache entry to be re-resolved, as it
  might resolve as a completely different file, or even resolve as
  a file when it was originally a directory and so forth.

* Fixes inconsistencies in the current-dir fields in proc->p_fd.

* Note that most VFS's can't re-resolve a disconnected directory
  anyway but HAMMER1 actually can, so this was causing a problem
  in tests with HAMMER1 (the same tests that originally crashed
  tmpfs were also crashing HAMMER1, but for a different reason).

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index bbd46e8..d4899d3 100644 (file)
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -2596,6 +2596,20 @@ restart:
        }
 
        /*
+        * If the ncp was destroyed it will never resolve again.  This
+        * can basically only happen when someone is chdir'd into an
+        * empty directory which is then rmdir'd.  We want to catch this
+        * here and not dive the VFS because the VFS might actually
+        * have a way to re-resolve the disconnected ncp, which will
+        * result in inconsistencies in the cdir/nch for proc->p_fd.
+        */
+       if (ncp->nc_flag & NCF_DESTROYED) {
+               kprintf("Warning: cache_resolve: ncp '%s' was unlinked\n",
+                       ncp->nc_name);
+               return(EINVAL);
+       }
+
+       /*
         * Mount points need special handling because the parent does not
         * belong to the same filesystem as the ncp.
         */