sysdeps/unix/sysv/linux/preadv64v2.c

   1 /* Linux implementation of preadv2 (LFS version).
   2    Copyright (C) 2017-2018 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 #if !defined(__NR_preadv64v2) && defined(__NR_preadv2)
  23 # define __NR_preadv64v2 __NR_preadv2
  24 #endif
  25
  26 ssize_t
  27 preadv64v2 (int fd, const struct iovec *vector, int count, off64_t offset,
  28             int flags)
  29 {
  30 #ifdef __NR_preadv64v2
  31   ssize_t result = SYSCALL_CANCEL (preadv64v2, fd, vector, count,
  32                                    LO_HI_LONG (offset), flags);
  33   if (result >= 0)
  34     return result;
  35 #endif
  36   /* Trying to emulate the preadv2 syscall flags is troublesome:
  37
  38      * We can not temporary change the file state of the O_DSYNC and O_SYNC
  39        flags to emulate RWF_{D}SYNC (attempts to change the state of using
  40        fcntl are silently ignored).
  41
  42      * IOCB_HIPRI requires the file opened in O_DIRECT and uses an internal
  43        semantic not provided by any other flag (O_NONBLOCK for instance).  */
  44
  45   if (flags != 0)
  46     {
  47       __set_errno (ENOTSUP);
  48       return -1;
  49     }
  50
  51   if (offset == -1)
  52     return __readv (fd, vector, count);
  53   else
  54     return preadv64 (fd, vector, count, offset);
  55 }
  56
  57 #ifdef __OFF_T_MATCHES_OFF64_T
  58 strong_alias (preadv64v2, preadv2)
  59 #endif