thin-provisioning-tools/base/file_utils.cc

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#include "base/file_utils.h"
#include "base/error_string.h"
#include <sstream>
#include <stdexcept>
#include <linux/fs.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
//----------------------------------------------------------------
// FIXME: give this namespace a name
namespace {
using namespace std;
int const DEFAULT_MODE = 0666;
int const OPEN_FLAGS = O_DIRECT;
// FIXME: introduce a new exception for this, or at least lift this
// to exception.h
void syscall_failed(char const *call) {
ostringstream out;
out << "syscall '" << call << "' failed: " << base::error_string(errno);
throw runtime_error(out.str());
}
void syscall_failed(string const &call, string const &message)
{
ostringstream out;
out << "syscall '" << call << "' failed: " << base::error_string(errno) << "\n"
<< message;
throw runtime_error(out.str());
}
}
//----------------------------------------------------------------
file_utils::file_descriptor::file_descriptor(string const &path, int flags) {
fd_ = ::open(path.c_str(), OPEN_FLAGS | flags, DEFAULT_MODE);
if (fd_ < 0)
syscall_failed("open",
"Note: you cannot run this tool with these options on live metadata.");
}
file_utils::file_descriptor::~file_descriptor() {
close(fd_);
fd_ = -1;
}
bool
file_utils::file_exists(string const &path) {
struct ::stat info;
int r = ::stat(path.c_str(), &info);
if (r) {
if (errno == ENOENT)
return false;
syscall_failed("stat");
return false; // never get here
} else
return S_ISREG(info.st_mode) || S_ISBLK(info.st_mode);
}
void
file_utils::check_file_exists(string const &file, bool must_be_regular_file) {
struct stat info;
int r = ::stat(file.c_str(), &info);
if (r)
throw runtime_error("Couldn't stat file");
if (must_be_regular_file && !S_ISREG(info.st_mode))
throw runtime_error("Not a regular file");
}
file_utils::file_descriptor
file_utils::create_block_file(string const &path, off_t file_size) {
if (file_exists(path)) {
ostringstream out;
out << __FUNCTION__ << ": file '" << path << "' already exists";
throw runtime_error(out.str());
}
file_descriptor fd(path, O_CREAT | O_EXCL | O_RDWR);
int r = ::ftruncate(fd.fd_, file_size);
if (r < 0)
syscall_failed("ftruncate");
return fd;
}
file_utils::file_descriptor
file_utils::open_block_file(string const &path, off_t min_size, bool writeable, bool excl) {
if (!file_exists(path)) {
ostringstream out;
out << __FUNCTION__ << ": file '" << path << "' doesn't exist";
throw runtime_error(out.str());
}
int flags = writeable ? O_RDWR : O_RDONLY;
if (excl)
flags |= O_EXCL;
return file_descriptor(path, flags);
}
uint64_t
file_utils::get_file_length(string const &file) {
struct stat info;
uint64_t nr_bytes;
int r = ::stat(file.c_str(), &info);
if (r)
throw runtime_error("Couldn't stat path");
if (S_ISREG(info.st_mode))
// It's okay to cast st_size to a uint64_t value.
// If LFS is enabled, st_size should not be negative for regular files.
nr_bytes = static_cast<uint64_t>(info.st_size);
else if (S_ISBLK(info.st_mode)) {
// To get the size of a block device we need to
// open it, and then make an ioctl call.
int fd = ::open(file.c_str(), O_RDONLY);
if (fd < 0)
throw runtime_error("couldn't open block device to ascertain size");
r = ::ioctl(fd, BLKGETSIZE64, &nr_bytes);
if (r) {
::close(fd);
throw runtime_error("ioctl BLKGETSIZE64 failed");
}
::close(fd);
} else
// FIXME: needs a better message
throw runtime_error("bad path");
return nr_bytes;
}
void
file_utils::zero_superblock(std::string const &path)
{
char *buffer;
unsigned const SUPERBLOCK_SIZE = 4096;
file_descriptor fd = open_block_file(path, SUPERBLOCK_SIZE, true, true);
buffer = reinterpret_cast<char *>(aligned_alloc(SUPERBLOCK_SIZE, SUPERBLOCK_SIZE));
if (!buffer)
throw runtime_error("out of memory");
memset(buffer, 0, SUPERBLOCK_SIZE);
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if (::write(fd.fd_, buffer, SUPERBLOCK_SIZE) != SUPERBLOCK_SIZE) {
free(buffer);
throw runtime_error("couldn't zero superblock");
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}
}
//----------------------------------------------------------------