tests/cp/nfs-removal-race

   1 #!/bin/sh
   2 # Running cp S D on an NFS client while another client has just removed D
   3 # would lead (w/coreutils-8.16 and earlier) to cp's initial stat call
   4 # seeing (via stale NFS cache) that D exists, so that cp would then call
   5 # open without the O_CREAT flag.  Yet, the open must actually consult
   6 # the server, which confesses that D has been deleted, thus causing the
   7 # open call to fail with ENOENT.
   8 #
   9 # This test simulates that situation by intercepting stat for a nonexistent
  10 # destination, D, and making the stat fill in the result struct for another
  11 # file and return 0.
  12 #
  13 # This test is skipped on systems that lack LD_PRELOAD support; that's fine.
  14 # Similarly, on a system that lacks <dlfcn.h> or __xstat, skipping it is fine.
  15
  16 # Copyright (C) 2012 Free Software Foundation, Inc.
  17
  18 # This program is free software: you can redistribute it and/or modify
  19 # it under the terms of the GNU General Public License as published by
  20 # the Free Software Foundation, either version 3 of the License, or
  21 # (at your option) any later version.
  22
  23 # This program is distributed in the hope that it will be useful,
  24 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  25 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  26 # GNU General Public License for more details.
  27
  28 # You should have received a copy of the GNU General Public License
  29 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  30
  31 . "${srcdir=.}/init.sh"; path_prepend_ ../src
  32 print_ver_ cp
  33
  34 # Replace each stat call with a call to this wrapper.
  35 cat > k.c <<'EOF' || framework_failure_
  36 #define _GNU_SOURCE
  37 #include <sys/types.h>
  38 #include <dlfcn.h>
  39
  40 #define __xstat __xstat_orig
  41
  42 #include <sys/stat.h>
  43 #include <stddef.h>
  44
  45 #undef __xstat
  46
  47 int
  48 __xstat (int ver, const char *path, struct stat *st)
  49 {
  50   static int (*real_stat)(int ver, const char *path, struct stat *st) = NULL;
  51   if (!real_stat)
  52     real_stat = dlsym (RTLD_NEXT, "__xstat");
  53   /* When asked to stat nonexistent "d",
  54      return results suggesting it exists. */
  55   return real_stat (ver, *path == 'd' && path[1] == 0 ? "d2" : path, st);
  56 }
  57 EOF
  58
  59 # Then compile/link it:
  60 $CC -shared -fPIC -O2 k.c -o k.so \
  61   || framework_failure_ 'failed to compile with -shared -fPIC'
  62
  63 touch d2 || framework_failure_
  64 echo xyz > src || framework_failure_
  65
  66 # Finally, run the test:
  67 LD_PRELOAD=./k.so cp src d || fail=1
  68
  69 compare src d || fail=1
  70 Exit $fail