/*
* Copyright 2018, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* fallocate_detect -- checks fallocate support on filesystem
*/
#define _GNU_SOURCE
#include "file.h"
#include "os.h"
#ifdef __linux__
#include <errno.h>
#include <fcntl.h>
#include <linux/magic.h>
#include <sys/vfs.h>
/*
* posix_fallocate on Linux is implemented using fallocate
* syscall. This syscall requires file system-specific code on
* the kernel side and not all file systems have this code.
* So when posix_fallocate gets 'not supported' error from
* fallocate it falls back to just writing zeroes.
* Detect it and return information to the caller.
*/
static int
check_fallocate(const char *file)
{
int exit_code = 0;
int fd = os_open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
if (fd < 0) {
perror("os_open");
return 2;
}
if (fallocate(fd, 0, 0, 4096)) {
if (errno == EOPNOTSUPP) {
exit_code = 1;
goto exit;
}
perror("fallocate");
exit_code = 2;
goto exit;
}
struct statfs fs;
if (!fstatfs(fd, &fs)) {
if (fs.f_type != EXT4_SUPER_MAGIC /* also ext2, ext3 */) {
/*
* On CoW filesystems, fallocate reserves _amount
* of_ space but doesn't allocate a specific block.
* As we're interested in DAX filesystems only, just
* skip these tests anywhere else.
*/
exit_code = 1;
goto exit;
}
}
exit:
os_close(fd);
os_unlink(file);
return exit_code;
}
#else
/* no support for fallocate in FreeBSD */
static int
check_fallocate(const char *file)
{
return 1;
}
#endif
int
main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "usage: %s filename\n", argv[0]);
return 1;
}
return check_fallocate(argv[1]);
}