Filesystem: Reference counting for locations

 o A new data structure rtems_filesystem_global_location_t was
   introduced to be used for
    o the mount point location in the mount table entry,
    o the file system root location in the mount table entry,
    o the root directory location in the user environment, and
    o the current directory location in the user environment.
   During the path evaluation global start locations are obtained to
   ensure that the current file system instance will be not unmounted in
   the meantime.
 o The user environment uses now reference counting and is protected
   from concurrent access.
 o The path evaluation process was completely rewritten and simplified.
   The IMFS, RFS, NFS, and DOSFS use now a generic path evaluation
   method.  Recursive calls in the path evaluation have been replaced
   with iteration to avoid stack overflows.  Only the evaluation of
   symbolic links is recursive.  No dynamic memory allocations and
   intermediate buffers are used in the high level path evaluation.  No
   global locks are held during the file system instance specific path
   evaluation process.
 o Recursive symbolic link evaluation is now limited by
   RTEMS_FILESYSTEM_SYMLOOP_MAX.  Applications can retrieve this value
   via sysconf().
 o The device file system (devFS) uses now no global variables and
   allocation from the workspace.  Node names are allocated from the
   heap.
 o The upper layer lseek() performs now some parameter checks.
 o The upper layer ftruncate() performs now some parameter checks.
 o unmask() is now restricted to the RWX flags and protected from
   concurrent access.
 o The fchmod_h and rmnod_h file system node handlers are now a file
   system operation.
 o The unlink_h operation has been removed.  All nodes are now destroyed
   with the rmnod_h operation.
 o New lock_h, unlock_h, clonenod_h, and are_nodes_equal_h file system
   operations.
 o The path evaluation and file system operations are now protected by
   per file system instance lock and unlock operations.
 o Fix and test file descriptor duplicate in fcntl().
 o New test fstests/fsnofs01.

1 files changed, 239 insertions, 8 deletions

diff --git a/cpukit/libcsupport/src/__usrenv.c b/cpukit/libcsupport/src/__usrenv.c
index 0b3469fa1a..d26e73658f 100644
--- a/cpukit/libcsupport/src/__usrenv.c
+++ b/cpukit/libcsupport/src/__usrenv.c
@@ -2,6 +2,9 @@
  *  COPYRIGHT (c) 1989-2008.
  *  On-Line Applications Research Corporation (OAR).
  *
+ *  Modifications to support reference counting in the file system are
+ *  Copyright (c) 2012 embedded brains GmbH.
+ *
  *  The license and distribution terms for this file may be
  *  found in the file LICENSE in this distribution or at
  *  http://www.rtems.com/license/LICENSE.
@@ -10,18 +13,246 @@
  */
 
 #if HAVE_CONFIG_H
-#include "config.h"
+  #include "config.h"
 #endif
 
-#include <rtems.h>
-#include <rtems/libio.h>
+#include <sys/stat.h>
+
 #include <rtems/libio_.h>
 
-/*
- *  Global information for POSIX Process Environment Support
- */
+static int null_handler_open(
+  rtems_libio_t *iop,
+  const char *path,
+  int oflag,
+  mode_t mode
+)
+{
+  return -1;
+}
+
+static int null_handler_fstat(
+  const rtems_filesystem_location_info_t *pathloc,
+  struct stat *buf
+)
+{
+  return -1;
+}
+
+const rtems_filesystem_file_handlers_r rtems_filesystem_null_handlers = {
+  .open_h = null_handler_open,
+  .close_h = rtems_filesystem_default_close,
+  .read_h = rtems_filesystem_default_read,
+  .write_h = rtems_filesystem_default_write,
+  .ioctl_h = rtems_filesystem_default_ioctl,
+  .lseek_h = rtems_filesystem_default_lseek,
+  .fstat_h = null_handler_fstat,
+  .ftruncate_h = rtems_filesystem_default_ftruncate,
+  .fsync_h = rtems_filesystem_default_fsync,
+  .fdatasync_h = rtems_filesystem_default_fdatasync,
+  .fcntl_h = rtems_filesystem_default_fcntl
+};
+
+static void null_op_lock_or_unlock(
+  rtems_filesystem_mount_table_entry_t *mt_entry
+)
+{
+  /* Do nothing */
+}
+
+static int null_op_mknod(
+  const rtems_filesystem_location_info_t *parentloc,
+  const char *name,
+  size_t namelen,
+  mode_t mode,
+  dev_t dev
+)
+{
+  return -1;
+}
+
+static int null_op_rmnod(
+  const rtems_filesystem_location_info_t *parentloc,
+  const rtems_filesystem_location_info_t *loc
+)
+{
+  return -1;
+}
+
+static int null_op_link(
+  const rtems_filesystem_location_info_t *parentloc,
+  const rtems_filesystem_location_info_t *targetloc,
+  const char *name,
+  size_t namelen
+)
+{
+  return -1;
+}
+
+static int null_op_fchmod(
+  const rtems_filesystem_location_info_t *pathloc,
+  mode_t mode
+)
+{
+  return -1;
+}
+
+static int null_op_chown(
+  const rtems_filesystem_location_info_t *loc,
+  uid_t owner,
+  gid_t group
+)
+{
+  return -1;
+}
+
+static int null_op_clonenode(
+  rtems_filesystem_location_info_t *loc
+)
+{
+  return -1;
+}
+
+static int null_op_mount(
+  rtems_filesystem_mount_table_entry_t *mt_entry
+)
+{
+  return -1;
+}
+
+static int null_op_fsmount_me(
+  rtems_filesystem_mount_table_entry_t *mt_entry,
+  const void *data
+)
+{
+  return -1;
+}
+
+static int null_op_unmount(
+  rtems_filesystem_mount_table_entry_t *mt_entry
+)
+{
+  return -1;
+}
+
+static void null_op_fsunmount_me(
+  rtems_filesystem_mount_table_entry_t *mt_entry
+)
+{
+  /* Do nothing */
+}
+
+static int null_op_utime(
+  const rtems_filesystem_location_info_t *loc,
+  time_t actime,
+  time_t modtime
+)
+{
+  return -1;
+}
+
+static int null_op_symlink(
+  const rtems_filesystem_location_info_t *parentloc,
+  const char *name,
+  size_t namelen,
+  const char *target
+)
+{
+  return -1;
+}
+
+static ssize_t null_op_readlink(
+  const rtems_filesystem_location_info_t *loc,
+  char *buf,
+  size_t bufsize
+)
+{
+  return -1;
+}
+
+static int null_op_rename(
+  const rtems_filesystem_location_info_t *oldparentloc,
+  const rtems_filesystem_location_info_t *oldloc,
+  const rtems_filesystem_location_info_t *newparentloc,
+  const char *name,
+  size_t namelen
+)
+{
+  return -1;
+}
+
+static int null_op_statvfs(
+  const rtems_filesystem_location_info_t *loc,
+  struct statvfs *buf
+)
+{
+  return -1;
+}
+
+static const rtems_filesystem_operations_table null_ops = {
+  .lock_h = null_op_lock_or_unlock,
+  .unlock_h = null_op_lock_or_unlock,
+  .eval_path_h = rtems_filesystem_default_eval_path,
+  .link_h = null_op_link,
+  .are_nodes_equal_h = rtems_filesystem_default_are_nodes_equal,
+  .node_type_h = rtems_filesystem_default_node_type,
+  .mknod_h = null_op_mknod,
+  .rmnod_h = null_op_rmnod,
+  .fchmod_h = null_op_fchmod,
+  .chown_h = null_op_chown,
+  .clonenod_h = null_op_clonenode,
+  .freenod_h = rtems_filesystem_default_freenode,
+  .mount_h = null_op_mount,
+  .fsmount_me_h = null_op_fsmount_me,
+  .unmount_h = null_op_unmount,
+  .fsunmount_me_h = null_op_fsunmount_me,
+  .utime_h = null_op_utime,
+  .symlink_h = null_op_symlink,
+  .readlink_h = null_op_readlink,
+  .rename_h = null_op_rename,
+  .statvfs_h = null_op_statvfs
+};
+
+rtems_filesystem_mount_table_entry_t rtems_filesystem_null_mt_entry = {
+  .location_chain = {
+    .Head = {
+      .Node = {
+        .next = &rtems_filesystem_global_location_null.location.mt_entry_node,
+        .previous = NULL
+      },
+      .fill = &rtems_filesystem_global_location_null.location.mt_entry_node,
+    }
+  },
+  .mt_point_node = &rtems_filesystem_global_location_null,
+  .mt_fs_root = &rtems_filesystem_global_location_null,
+  .mounted = false,
+  .writeable = false
+};
+
+rtems_filesystem_global_location_t rtems_filesystem_global_location_null = {
+  .location = {
+    .mt_entry_node = {
+      .next = &rtems_filesystem_null_mt_entry.location_chain.Tail.Node,
+      .previous = &rtems_filesystem_null_mt_entry.location_chain.Head.Node
+    },
+    .handlers = &rtems_filesystem_null_handlers,
+    .ops = &null_ops,
+    .mt_entry = &rtems_filesystem_null_mt_entry
+  },
 
-rtems_user_env_t   rtems_global_user_env;
-rtems_user_env_t * rtems_current_user_env = &rtems_global_user_env;
+  /*
+   * The initial reference count accounts for the following references
+   *  o the root directory of the user environment,
+   *  o the current directory of the user environment,
+   *  o the root node of the null file system instance, and
+   *  o the mount point node of the null file system instance.
+   */
+  .reference_count = 4
+};
 
+rtems_user_env_t rtems_global_user_env = {
+  .current_directory = &rtems_filesystem_global_location_null,
+  .root_directory = &rtems_filesystem_global_location_null,
+  .umask = S_IWGRP | S_IWOTH
+};
 
+rtems_user_env_t *rtems_current_user_env = &rtems_global_user_env;