WebSVN – HelenOS – Diff – /trunk/uspace/srv/vfs/vfs_open.c

 /*
  * Copyright (c) 2007 Jakub Jermar
  * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
+ *
  * - Redistributions of source code must retain the above copyright
  *   notice, this list of conditions and the following disclaimer.
  * - Redistributions in binary form must reproduce the above copyright
  *   notice, this list of conditions and the following disclaimer in the
  *   documentation and/or other materials provided with the distribution.
  * - The name of the author may not be used to endorse or promote products
  *   derived from this software without specific prior written permission.
+ *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 /** @addtogroup fs
  * @{
  */
 /**
  * @file    vfs_open.c
  * @brief   VFS_OPEN method.
  */
 #include <ipc/ipc.h>
 #include <async.h>
 #include <errno.h>
-#include <stdlib.h>
-#include <string.h>
-#include <bool.h>
 #include <futex.h>
-#include <libadt/list.h>
 #include <sys/types.h>
+#include <stdlib.h>
 #include "vfs.h"
-/** Per-connection futex protecting the files array. */
-__thread atomic_t files_futex = FUTEX_INITIALIZER;
-/**
- * This is a per-connection table of open files.
- * Our assumption is that each client opens only one connection and therefore
- * there is one table of open files per task. However, this may not be the case
- * and the client can open more connections to VFS. In that case, there will be
- * several tables and several file handle name spaces per task. Besides of this,
- * the functionality will stay unchanged. So unless the client knows what it is
- * doing, it should open one connection to VFS only.
- *
- * Allocation of the open files table is deferred until the client makes the
- * first VFS_OPEN operation.
- */
-__thread vfs_file_t *files = NULL;
-/** Initialize the table of open files. */
-static bool vfs_conn_open_files_init(void)
-{
-    /*
-     * Optimized fast path that will never go to sleep unnecessarily.
-     * The assumption is that once files is non-zero, it will never be zero
-     * again.
-     */
-    if (files)
-        return true;
-    futex_down(&files_futex);
-    if (!files) {
-        files = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t));
-        if (!files) {
-            futex_up(&files_futex);
-            return false;
-        }
-        memset(files, 0, MAX_OPEN_FILES * sizeof(vfs_file_t));
-    }
-    futex_up(&files_futex);
-    return true;
-}
 void vfs_open(ipc_callid_t rid, ipc_call_t *request)
+{
-    if (!vfs_conn_open_files_init()) {
+    if (!vfs_files_init()) {
         ipc_answer_fast_0(rid, ENOMEM);
         return;
+    }
     /*
      * The POSIX interface is open(path, flags, mode).
      * We can receive flags and mode along with the VFS_OPEN call; the path
      * will need to arrive in another call.
      */
     int flags = IPC_GET_ARG1(*request);
     int mode = IPC_GET_ARG2(*request);
     size_t size;
     ipc_callid_t callid;
     ipc_call_t call;
     if (!ipc_data_receive(&callid, &call, NULL, &size)) {
         ipc_answer_fast_0(callid, EINVAL);
         ipc_answer_fast_0(rid, EINVAL);
         return;
+    }
     /*
      * Now we are on the verge of accepting the path.
+     *
      * There is one optimization we could do in the future: copy the path
      * directly into the PLB using some kind of a callback.
      */
     char *path = malloc(size);
     if (!path) {
         ipc_answer_fast_0(callid, ENOMEM);
         ipc_answer_fast_0(rid, ENOMEM);
         return;
+    }
     int rc;
-    if (rc = ipc_data_deliver(callid, &call, path, size)) {
+    if ((rc = ipc_data_deliver(callid, &call, path, size))) {
         ipc_answer_fast_0(rid, rc);
         free(path);
         return;
+    }
     /*
+     * Avoid the race condition in which the file can be deleted before we
+     * find/create-and-lock the VFS node corresponding to the looked-up
+     * triplet.
+     */
+    futex_down(&unlink_futex);
+    /*
      * The path is now populated and we can call vfs_lookup_internal().
      */
     vfs_triplet_t triplet;
     rc = vfs_lookup_internal(path, size, &triplet, NULL);
     if (rc) {
+        futex_up(&unlink_futex);
         ipc_answer_fast_0(rid, rc);
         free(path);
         return;
+    }
     /*
      * Path is no longer needed.
      */
     free(path);
     vfs_node_t *node = vfs_node_get(&triplet);
+    futex_up(&unlink_futex);
+    /*
+     * Get ourselves a file descriptor and the corresponding vfs_file_t
+     * structure.
+     */
+    int fd = vfs_fd_alloc();
+    if (fd < 0) {
+        vfs_node_put(node);
+        ipc_answer_fast_0(rid, fd);
+        return;
+    }
+    vfs_file_t *file = vfs_file_get(fd);
-    // TODO: not finished
+    file->node = node;
+    /*
+     * The following increase in reference count is for the fact that the
+     * file is being opened and that a file structure is pointing to it.
+     * It is necessary so that the file will not disappear when
+     * vfs_node_put() is called. The reference will be dropped by the
+     * respective VFS_CLOSE.
+     */
+    vfs_node_addref(node);
+    vfs_node_put(node);
+    /*
+     * Success! Return the new file descriptor to the client.
+     */
+    ipc_answer_fast_1(rid, EOK, fd);
+}
 /**
  * @}
  */

Subversion Repositories HelenOS

(root)/trunk/uspace/srv/vfs/vfs_open.c @ 2619 – Rev 2590 → 2593