sysdeps/unix/sysv/linux/preadv2.c

   1 /* Linux implementation of preadv2.
   2    Copyright (C) 2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/uio.h>
  20 #include <sysdep-cancel.h>
  21
  22 #ifndef __OFF_T_MATCHES_OFF64_T
  23
  24 # if !defined (__NR_preadv2) && defined (__NR_pread64v2)
  25 #  define __NR_preadv2 __NR_pread64v2
  26 # endif
  27
  28 ssize_t
  29 preadv2 (int fd, const struct iovec *vector, int count, off_t offset,
  30          int flags)
  31 {
  32 # ifdef __NR_preadv2
  33   ssize_t result = SYSCALL_CANCEL (preadv2, fd, vector, count,
  34                                    LO_HI_LONG (offset), flags);
  35   if (result >= 0)
  36     return result;
  37 # endif
  38   /* Trying to emulate the preadv2 syscall flags is troublesome:
  39
  40      * We can not temporary change the file state of the O_DSYNC and O_SYNC
  41        flags to emulate RWF_{D}SYNC (attempts to change the state of using
  42        fcntl are silently ignored).
  43
  44      * IOCB_HIPRI requires the file opened in O_DIRECT and uses an internal
  45        semantic not provided by any other flag (O_NONBLOCK for instance).  */
  46
  47   if (flags != 0)
  48     {
  49       __set_errno (ENOTSUP);
  50       return -1;
  51     }
  52   return preadv (fd, vector, count, offset);
  53 }
  54
  55 #endif