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, 69 insertions, 26 deletions

diff --git a/cpukit/include/rtems/userenv.h b/cpukit/include/rtems/userenv.h
index 28ac69ebd3..123da98af5 100644
--- a/cpukit/include/rtems/userenv.h
+++ b/cpukit/include/rtems/userenv.h
@@ -1,13 +1,16 @@
 /**
- * @file rtems/userenv.h
+ * @file
  *
- * This file defines the interface for POSIX per-process environment.
+ * @ingroup LibIOEnv
  */
 
 /*
  *  COPYRIGHT (c) 1989-2011.
  *  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.
@@ -18,6 +21,13 @@
 #ifndef _RTEMS_USERENV_H
 #define _RTEMS_USERENV_H
 
+/*
+ * According to IEEE Std 1003.1-2001,
+ * limits.h is supposed to provide _POSIX_LOGIN_NAME_MAX
+ * XXX: We do not rely on this.
+ */
+#include <limits.h>
+
 #include <rtems.h>
 #include <rtems/fs.h>
 
@@ -25,33 +35,30 @@
 extern "C" {
 #endif
 
-/*
- *  External structures
- */
-
-/*
- * According to IEEE Std 1003.1-2001,
- * limits.h is supposed to provide _POSIX_LOGIN_NAME_MAX
- * FIXME: We should not rely on this.
+/**
+ * @defgroup LibIOEnv User Environment
+ *
+ * @ingroup LibIO
+ *
+ * @brief Provides a POSIX like user environment for tasks.
+ *
+ * @{
  */
-#include <limits.h>
 
 #ifndef LOGIN_NAME_MAX
-#ifdef _POSIX_LOGIN_NAME_MAX
-#define LOGIN_NAME_MAX _POSIX_LOGIN_NAME_MAX
-#else
-/* Fallback */
-#define LOGIN_NAME_MAX 9
-#endif
+  #ifdef _POSIX_LOGIN_NAME_MAX
+    #define LOGIN_NAME_MAX _POSIX_LOGIN_NAME_MAX
+  #else
+    /* Fallback */
+    #define LOGIN_NAME_MAX 9
+  #endif
 #endif
 
 typedef struct {
-  rtems_id                         task_id;
-  rtems_filesystem_location_info_t current_directory;
-  rtems_filesystem_location_info_t root_directory;
+  rtems_filesystem_global_location_t *current_directory;
+  rtems_filesystem_global_location_t *root_directory;
   /* Default mode for all files. */
   mode_t                           umask;
-  nlink_t                          link_counts;
   /* _POSIX_types */
   uid_t                            uid;
   gid_t                            gid;
@@ -59,6 +66,9 @@ typedef struct {
   gid_t                            egid;
   char      login_buffer[LOGIN_NAME_MAX];
   pid_t                            pgrp; /* process group id */
+  /* User environment maintenance */
+  rtems_id                         task_id;
+  int                              reference_count;
 } rtems_user_env_t;
 
 extern rtems_user_env_t * rtems_current_user_env;
@@ -66,7 +76,6 @@ extern rtems_user_env_t   rtems_global_user_env;
 
 #define rtems_filesystem_current     (rtems_current_user_env->current_directory)
 #define rtems_filesystem_root        (rtems_current_user_env->root_directory)
-#define rtems_filesystem_link_counts (rtems_current_user_env->link_counts)
 #define rtems_filesystem_umask       (rtems_current_user_env->umask)
 
 #define _POSIX_types_Uid             (rtems_current_user_env->uid)
@@ -75,14 +84,48 @@ extern rtems_user_env_t   rtems_global_user_env;
 #define _POSIX_types_Egid            (rtems_current_user_env->egid)
 #define _POSIX_types_Getlogin_buffer (rtems_current_user_env->login_buffer)
 
-
-/*
- *  Instantiate a private copy of the per user information for the calling task.
+/**
+ * @brief Creates a private environment.
+ *
+ * If the task has already a private environment nothing will be changed.  This
+ * function must be called from normal thread context and may block on a mutex.
+ * Thread dispatching is disabled to protect some critical sections.
+ *
+ * @retval RTEMS_SUCCESSFUL Successful operation.
+ * @retval RTEMS_NO_MEMORY Not enough memory.
+ * @retval RTEMS_UNSATISFIED Cloning of the current environment failed.
+ * @retval RTEMS_TOO_MANY Cannot register the private environment.
  */
-
 rtems_status_code rtems_libio_set_private_env(void);
+
+/**
+ * @brief Creates a private environment shared with another task.
+ *
+ * An attempt to share the environment with itself has no effect.  This
+ * function must be called from normal thread context and may block on a mutex.
+ * Thread dispatching is disabled to protect some critical sections.
+ *
+ * @param[in] task_id The private environment is shared with the task specified
+ * by this identifier.
+ *
+ * @retval RTEMS_SUCCESSFUL Successful operation.
+ * @retval RTEMS_UNSATISFIED No shared environment is available for this task
+ * @retval RTEMS_TOO_MANY Cannot register the shared environment.
+ * identifier.
+ */
 rtems_status_code rtems_libio_share_private_env(rtems_id task_id) ;
 
+/**
+ * @brief Use the global environment.
+ *
+ * A private environment will be released.  This function may be called from
+ * every thread context.  Thread dispatching is disabled to protect the
+ * critical sections.
+ */
+void rtems_libio_use_global_env(void);
+
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif