sysdeps/unix/sysv/linux/preadv2.c

   1 /* Linux implementation of preadv2.
   2    Copyright (C) 2017-2024 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    <https://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 ssize_t
  25 preadv2 (int fd, const struct iovec *vector, int count, off_t offset,
  26          int flags)
  27 {
  28   ssize_t result = SYSCALL_CANCEL (preadv2, fd, vector, count,
  29                                    LO_HI_LONG (offset), flags);
  30   if (result >= 0 || errno != ENOSYS)
  31     return result;
  32
  33   /* Trying to emulate the preadv2 syscall flags is troublesome:
  34
  35      * We can not temporary change the file state of the O_DSYNC and O_SYNC
  36        flags to emulate RWF_{D}SYNC (attempts to change the state of using
  37        fcntl are silently ignored).
  38
  39      * IOCB_HIPRI requires the file opened in O_DIRECT and uses an internal
  40        semantic not provided by any other flag (O_NONBLOCK for instance).  */
  41
  42   if (flags != 0)
  43     {
  44       __set_errno (ENOTSUP);
  45       return -1;
  46     }
  47   if (offset == -1)
  48     return __readv (fd, vector, count);
  49   else
  50     return preadv (fd, vector, count, offset);
  51 }
  52
  53 #endif