zircon/system/ulib/fs/unmount.cc

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <fs/vfs.h>
#include <fuchsia/io/c/fidl.h>
#include <lib/fidl/txn_header.h>
#include <lib/zircon-internal/debug.h>
#include <lib/fdio/vfs.h>

#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

// Sends an 'unmount' signal on the srv handle, and waits until it is closed.
// Consumes 'srv'.
zx_status_t vfs_unmount_handle(zx_handle_t srv, zx_time_t deadline) {
  // TODO(smklein): Use C Bindings.
  uint8_t msg[FIDL_ALIGN(sizeof(fuchsia_io_DirectoryAdminUnmountRequest)) + FDIO_CHUNK_SIZE];
  auto request = reinterpret_cast<fuchsia_io_DirectoryAdminUnmountRequest*>(msg);
  auto response = reinterpret_cast<fuchsia_io_DirectoryAdminUnmountResponse*>(msg);

  // the only other messages we ever send are no-reply OPEN or CLONE with
  // txid of 0.
  zx_txid_t txid = 1;
  fidl_init_txn_header(&request->hdr, txid, fuchsia_io_DirectoryAdminUnmountGenOrdinal);

  zx_channel_call_args_t args;
  args.wr_bytes = request;
  args.wr_handles = NULL;
  args.rd_bytes = response;
  args.rd_handles = NULL;
  args.wr_num_bytes = FIDL_ALIGN(sizeof(fuchsia_io_DirectoryAdminUnmountRequest));
  args.wr_num_handles = 0;
  args.rd_num_bytes = FIDL_ALIGN(sizeof(fuchsia_io_DirectoryAdminUnmountResponse));
  args.rd_num_handles = 0;

  uint32_t dsize;
  uint32_t hcount;

  // At the moment, we don't actually care what the response is from the
  // filesystem server (or even if it supports the unmount operation). As
  // soon as ANY response comes back, either in the form of a closed handle
  // or a visible response, shut down.
  zx_status_t status = zx_channel_call(srv, 0, deadline, &args, &dsize, &hcount);
  if (status == ZX_OK) {
    // Read phase succeeded. If the target filesystem returned an error, we
    // should parse it.
    if (dsize < FIDL_ALIGN(sizeof(fuchsia_io_DirectoryAdminUnmountResponse))) {
      status = ZX_ERR_IO;
    } else {
      status = response->s;
    }
  }
  zx_handle_close(srv);
  return status;
}