glibc/sysdeps/posix/posix_fallocate64.c

/* Copyright (C) 2000-2013 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/statfs.h>

/* Reserve storage for the data of the file associated with FD.  */

int
__posix_fallocate64_l64 (int fd, __off64_t offset, __off64_t len)
{
  struct stat64 st;
  struct statfs64 f;

  /* `off64_t' is a signed type.  Therefore we can determine whether
     OFFSET + LEN is too large if it is a negative value.  */
  if (offset < 0 || len < 0)
    return EINVAL;
  if (offset + len < 0)
    return EFBIG;

  /* First thing we have to make sure is that this is really a regular
     file.  */
  if (__fxstat64 (_STAT_VER, fd, &st) != 0)
    return EBADF;
  if (S_ISFIFO (st.st_mode))
    return ESPIPE;
  if (! S_ISREG (st.st_mode))
    return ENODEV;

  if (len == 0)
    {
      if (st.st_size < offset)
	{
	  int ret = __ftruncate64 (fd, offset);

	  if (ret != 0)
	    ret = errno;
	  return ret;
	}
      return 0;
    }

  /* We have to know the block size of the filesystem to get at least some
     sort of performance.  */
  if (__fstatfs64 (fd, &f) != 0)
    return errno;

  /* Try to play safe.  */
  if (f.f_bsize == 0)
    f.f_bsize = 512;

  /* Write something to every block.  */
  for (offset += (len - 1) % f.f_bsize; len > 0; offset += f.f_bsize)
    {
      len -= f.f_bsize;

      if (offset < st.st_size)
	{
	  unsigned char c;
	  ssize_t rsize = __libc_pread64 (fd, &c, 1, offset);

	  if (rsize < 0)
	    return errno;
	  /* If there is a non-zero byte, the block must have been
	     allocated already.  */
	  else if (rsize == 1 && c != 0)
	    continue;
	}

      if (__libc_pwrite64 (fd, "", 1, offset) != 1)
	return errno;
    }

  return 0;
}

#undef __posix_fallocate64_l64
#include <shlib-compat.h>
#include <bits/wordsize.h>

#if __WORDSIZE == 32 && SHLIB_COMPAT(libc, GLIBC_2_2, GLIBC_2_3_3)

int
attribute_compat_text_section
__posix_fallocate64_l32 (int fd, off64_t offset, size_t len)
{
  return __posix_fallocate64_l64 (fd, offset, len);
}

versioned_symbol (libc, __posix_fallocate64_l64, posix_fallocate64,
		  GLIBC_2_3_3);
compat_symbol (libc, __posix_fallocate64_l32, posix_fallocate64, GLIBC_2_2);
#else
strong_alias (__posix_fallocate64_l64, posix_fallocate64);
#endif