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/* Stub for copy_file_range
Copyright 2019-2022 Free Software Foundation, Inc.
This file 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.
This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include <unistd.h>
#include <errno.h>
#if defined __linux__ && HAVE_COPY_FILE_RANGE
# include <sys/utsname.h>
#endif
ssize_t
copy_file_range (int infd, off_t *pinoff,
int outfd, off_t *poutoff,
size_t length, unsigned int flags)
{
#undef copy_file_range
#if defined __linux__ && HAVE_COPY_FILE_RANGE
/* The implementation of copy_file_range (which first appeared in
Linux kernel release 4.5) had many issues before release 5.3
<https://lwn.net/Articles/789527/>, so fail with ENOSYS for Linux
kernels 5.2 and earlier.
This workaround, and the configure-time check for Linux, can be
removed when such kernels (released March 2016 through September
2019) are no longer a consideration. As of January 2021, the
furthest-future planned kernel EOL is December 2024 for kernel
release 4.19. */
static signed char ok;
if (! ok)
{
struct utsname name;
uname (&name);
char *p = name.release;
ok = ((p[1] != '.' || '5' < p[0]
|| (p[0] == '5' && (p[3] != '.' || '2' < p[2])))
? 1 : -1);
}
if (0 < ok)
return copy_file_range (infd, pinoff, outfd, poutoff, length, flags);
#endif
/* There is little need to emulate copy_file_range with read+write,
since programs that use copy_file_range must fall back on
read+write anyway. */
errno = ENOSYS;
return -1;
}
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