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rocksdb/util/env_posix.cc

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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include <deque>
#include <set>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <time.h>
#include <unistd.h>
#if defined(OS_LINUX)
#include <linux/fs.h>
#endif
#if defined(LEVELDB_PLATFORM_ANDROID)
#include <sys/stat.h>
#endif
#include "leveldb/env.h"
#include "leveldb/slice.h"
#include "port/port.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/posix_logger.h"
#if !defined(TMPFS_MAGIC)
#define TMPFS_MAGIC 0x01021994
#endif
#if !defined(XFS_SUPER_MAGIC)
#define XFS_SUPER_MAGIC 0x58465342
#endif
#if !defined(EXT4_SUPER_MAGIC)
#define EXT4_SUPER_MAGIC 0xEF53
#endif
bool useOsBuffer = 1; // cache data in OS buffers
bool useFsReadAhead = 1; // allow filesystem to do readaheads
bool useMmapRead = 0; // do not use mmaps for reading files
bool useMmapWrite = 1; // use mmaps for appending to files
namespace leveldb {
namespace {
// list of pathnames that are locked
static std::set<std::string> lockedFiles;
static port::Mutex mutex_lockedFiles;
static Status IOError(const std::string& context, int err_number) {
return Status::IOError(context, strerror(err_number));
}
class PosixSequentialFile: public SequentialFile {
private:
std::string filename_;
FILE* file_;
int fd_;
bool use_os_buffer = true;
public:
PosixSequentialFile(const std::string& fname, FILE* f,
const EnvOptions& options)
: filename_(fname), file_(f) {
fd_ = fileno(f);
assert(!options.UseMmapReads());
use_os_buffer = options.UseOsBuffer();
}
virtual ~PosixSequentialFile() { fclose(file_); }
virtual Status Read(size_t n, Slice* result, char* scratch) {
Status s;
size_t r = fread_unlocked(scratch, 1, n, file_);
*result = Slice(scratch, r);
if (r < n) {
if (feof(file_)) {
// We leave status as ok if we hit the end of the file
} else {
// A partial read with an error: return a non-ok status
s = IOError(filename_, errno);
}
}
if (!use_os_buffer) {
// we need to fadvise away the entire range of pages because
// we do not want readahead pages to be cached.
posix_fadvise(fd_, 0, 0, POSIX_FADV_DONTNEED); // free OS pages
}
return s;
}
virtual Status Skip(uint64_t n) {
if (fseek(file_, n, SEEK_CUR)) {
return IOError(filename_, errno);
}
return Status::OK();
}
};
// pread() based random-access
class PosixRandomAccessFile: public RandomAccessFile {
private:
std::string filename_;
int fd_;
bool use_os_buffer = true;
public:
PosixRandomAccessFile(const std::string& fname, int fd,
const EnvOptions& options)
: filename_(fname), fd_(fd) {
assert(!options.UseMmapReads());
if (!options.UseReadahead()) { // disable read-aheads
posix_fadvise(fd, 0, 0, POSIX_FADV_RANDOM);
}
use_os_buffer = options.UseOsBuffer();
}
virtual ~PosixRandomAccessFile() { close(fd_); }
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
Status s;
ssize_t r = pread(fd_, scratch, n, static_cast<off_t>(offset));
*result = Slice(scratch, (r < 0) ? 0 : r);
if (r < 0) {
// An error: return a non-ok status
s = IOError(filename_, errno);
}
if (!use_os_buffer) {
// we need to fadvise away the entire range of pages because
// we do not want readahead pages to be cached.
posix_fadvise(fd_, 0, 0, POSIX_FADV_DONTNEED); // free OS pages
}
return s;
}
#if defined(OS_LINUX)
virtual size_t GetUniqueId(char* id, size_t max_size) const {
// TODO: possibly allow this function to handle tighter bounds.
if (max_size < kMaxVarint64Length*3) {
return 0;
}
struct stat buf;
int result = fstat(fd_, &buf);
if (result == -1) {
return 0;
}
long version = 0;
result = ioctl(fd_, FS_IOC_GETVERSION, &version);
if (result == -1) {
return 0;
}
uint64_t uversion = (uint64_t)version;
char* rid = id;
rid = EncodeVarint64(rid, buf.st_dev);
rid = EncodeVarint64(rid, buf.st_ino);
rid = EncodeVarint64(rid, uversion);
assert(rid >= id);
return static_cast<size_t>(rid-id);
}
#endif
};
// mmap() based random-access
class PosixMmapReadableFile: public RandomAccessFile {
private:
std::string filename_;
void* mmapped_region_;
size_t length_;
public:
// base[0,length-1] contains the mmapped contents of the file.
PosixMmapReadableFile(const std::string& fname, void* base, size_t length,
const EnvOptions& options)
: filename_(fname), mmapped_region_(base), length_(length) {
assert(options.UseMmapReads());
assert(options.UseOsBuffer());
assert(options.UseReadahead());
}
virtual ~PosixMmapReadableFile() { munmap(mmapped_region_, length_); }
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
Status s;
if (offset + n > length_) {
*result = Slice();
s = IOError(filename_, EINVAL);
} else {
*result = Slice(reinterpret_cast<char*>(mmapped_region_) + offset, n);
}
return s;
}
};
// We preallocate up to an extra megabyte and use memcpy to append new
// data to the file. This is safe since we either properly close the
// file before reading from it, or for log files, the reading code
// knows enough to skip zero suffixes.
class PosixMmapFile : public WritableFile {
private:
std::string filename_;
int fd_;
size_t page_size_;
size_t map_size_; // How much extra memory to map at a time
char* base_; // The mapped region
char* limit_; // Limit of the mapped region
char* dst_; // Where to write next (in range [base_,limit_])
char* last_sync_; // Where have we synced up to
uint64_t file_offset_; // Offset of base_ in file
// Have we done an munmap of unsynced data?
bool pending_sync_;
// Roundup x to a multiple of y
static size_t Roundup(size_t x, size_t y) {
return ((x + y - 1) / y) * y;
}
size_t TruncateToPageBoundary(size_t s) {
s -= (s & (page_size_ - 1));
assert((s % page_size_) == 0);
return s;
}
bool UnmapCurrentRegion() {
bool result = true;
if (base_ != nullptr) {
if (last_sync_ < limit_) {
// Defer syncing this data until next Sync() call, if any
pending_sync_ = true;
}
if (munmap(base_, limit_ - base_) != 0) {
result = false;
}
file_offset_ += limit_ - base_;
base_ = nullptr;
limit_ = nullptr;
last_sync_ = nullptr;
dst_ = nullptr;
// Increase the amount we map the next time, but capped at 1MB
if (map_size_ < (1<<20)) {
map_size_ *= 2;
}
}
return result;
}
Status MapNewRegion() {
assert(base_ == nullptr);
int alloc_status = posix_fallocate(fd_, file_offset_, map_size_);
if (alloc_status != 0) {
return Status::IOError("Error allocating space to file : " + filename_ +
"Error : " + strerror(alloc_status));
}
void* ptr = mmap(nullptr, map_size_, PROT_READ | PROT_WRITE, MAP_SHARED,
fd_, file_offset_);
if (ptr == MAP_FAILED) {
return Status::IOError("MMap failed on " + filename_);
}
base_ = reinterpret_cast<char*>(ptr);
limit_ = base_ + map_size_;
dst_ = base_;
last_sync_ = base_;
return Status::OK();
}
public:
PosixMmapFile(const std::string& fname, int fd, size_t page_size,
const EnvOptions& options)
: filename_(fname),
fd_(fd),
page_size_(page_size),
map_size_(Roundup(65536, page_size)),
base_(nullptr),
limit_(nullptr),
dst_(nullptr),
last_sync_(nullptr),
file_offset_(0),
pending_sync_(false) {
assert((page_size & (page_size - 1)) == 0);
assert(options.UseMmapWrites());
}
~PosixMmapFile() {
if (fd_ >= 0) {
PosixMmapFile::Close();
}
}
virtual Status Append(const Slice& data) {
const char* src = data.data();
size_t left = data.size();
PrepareWrite(GetFileSize(), left);
while (left > 0) {
assert(base_ <= dst_);
assert(dst_ <= limit_);
size_t avail = limit_ - dst_;
if (avail == 0) {
if (UnmapCurrentRegion()) {
Status s = MapNewRegion();
if (!s.ok()) {
return s;
}
}
}
size_t n = (left <= avail) ? left : avail;
memcpy(dst_, src, n);
dst_ += n;
src += n;
left -= n;
}
return Status::OK();
}
virtual Status Close() {
Status s;
size_t unused = limit_ - dst_;
if (!UnmapCurrentRegion()) {
s = IOError(filename_, errno);
} else if (unused > 0) {
// Trim the extra space at the end of the file
if (ftruncate(fd_, file_offset_ - unused) < 0) {
s = IOError(filename_, errno);
}
}
if (close(fd_) < 0) {
if (s.ok()) {
s = IOError(filename_, errno);
}
}
fd_ = -1;
base_ = nullptr;
limit_ = nullptr;
return s;
}
virtual Status Flush() {
return Status::OK();
}
virtual Status Sync() {
Status s;
if (pending_sync_) {
// Some unmapped data was not synced
pending_sync_ = false;
if (fdatasync(fd_) < 0) {
s = IOError(filename_, errno);
}
}
if (dst_ > last_sync_) {
// Find the beginnings of the pages that contain the first and last
// bytes to be synced.
size_t p1 = TruncateToPageBoundary(last_sync_ - base_);
size_t p2 = TruncateToPageBoundary(dst_ - base_ - 1);
last_sync_ = dst_;
if (msync(base_ + p1, p2 - p1 + page_size_, MS_SYNC) < 0) {
s = IOError(filename_, errno);
}
}
return s;
}
/**
* Flush data as well as metadata to stable storage.
*/
virtual Status Fsync() {
if (pending_sync_) {
// Some unmapped data was not synced
pending_sync_ = false;
if (fsync(fd_) < 0) {
return IOError(filename_, errno);
}
}
// This invocation to Sync will not issue the call to
// fdatasync because pending_sync_ has already been cleared.
return Sync();
}
/**
* Get the size of valid data in the file. This will not match the
* size that is returned from the filesystem because we use mmap
* to extend file by map_size every time.
*/
virtual uint64_t GetFileSize() {
size_t used = dst_ - base_;
return file_offset_ + used;
}
#ifdef OS_LINUX
virtual Status Allocate(off_t offset, off_t len) {
if (!fallocate(fd_, FALLOC_FL_KEEP_SIZE, offset, len)) {
return Status::OK();
} else {
return IOError(filename_, errno);
}
}
#endif
};
// Use posix write to write data to a file.
class PosixWritableFile : public WritableFile {
private:
const std::string filename_;
int fd_;
size_t cursize_; // current size of cached data in buf_
size_t capacity_; // max size of buf_
unique_ptr<char[]> buf_; // a buffer to cache writes
uint64_t filesize_;
bool pending_sync_;
bool pending_fsync_;
public:
PosixWritableFile(const std::string& fname, int fd, size_t capacity,
const EnvOptions& options) :
filename_(fname),
fd_(fd),
cursize_(0),
capacity_(capacity),
buf_(new char[capacity]),
filesize_(0),
pending_sync_(false),
pending_fsync_(false) {
assert(!options.UseMmapWrites());
}
~PosixWritableFile() {
if (fd_ >= 0) {
PosixWritableFile::Close();
}
}
virtual Status Append(const Slice& data) {
char* src = (char *)data.data();
size_t left = data.size();
Status s;
pending_sync_ = true;
pending_fsync_ = true;
PrepareWrite(GetFileSize(), left);
// if there is no space in the cache, then flush
if (cursize_ + left > capacity_) {
s = Flush();
if (!s.ok()) {
return s;
}
// Increase the buffer size, but capped at 1MB
if (capacity_ < (1<<20)) {
capacity_ *= 2;
buf_.reset(new char[capacity_]);
}
assert(cursize_ == 0);
}
// if the write fits into the cache, then write to cache
// otherwise do a write() syscall to write to OS buffers.
if (cursize_ + left <= capacity_) {
memcpy(buf_.get()+cursize_, src, left);
cursize_ += left;
} else {
while (left != 0) {
ssize_t done = write(fd_, src, left);
if (done < 0) {
return IOError(filename_, errno);
}
left -= done;
src += done;
}
}
filesize_ += data.size();
return Status::OK();
}
virtual Status Close() {
Status s;
s = Flush(); // flush cache to OS
if (!s.ok()) {
}
if (close(fd_) < 0) {
if (s.ok()) {
s = IOError(filename_, errno);
}
}
fd_ = -1;
return s;
}
// write out the cached data to the OS cache
virtual Status Flush() {
size_t left = cursize_;
char* src = buf_.get();
while (left != 0) {
ssize_t done = write(fd_, src, left);
if (done < 0) {
return IOError(filename_, errno);
}
left -= done;
src += done;
}
cursize_ = 0;
return Status::OK();
}
virtual Status Sync() {
if (pending_sync_ && fdatasync(fd_) < 0) {
return IOError(filename_, errno);
}
pending_sync_ = false;
return Status::OK();
}
virtual Status Fsync() {
if (pending_fsync_ && fsync(fd_) < 0) {
return IOError(filename_, errno);
}
pending_fsync_ = false;
pending_sync_ = false;
return Status::OK();
}
virtual uint64_t GetFileSize() {
return filesize_;
}
#ifdef OS_LINUX
virtual Status Allocate(off_t offset, off_t len) {
if (!fallocate(fd_, FALLOC_FL_KEEP_SIZE, offset, len)) {
return Status::OK();
} else {
return IOError(filename_, errno);
}
}
#endif
};
static int LockOrUnlock(const std::string& fname, int fd, bool lock) {
mutex_lockedFiles.Lock();
if (lock) {
// If it already exists in the lockedFiles set, then it is already locked,
// and fail this lock attempt. Otherwise, insert it into lockedFiles.
// This check is needed because fcntl() does not detect lock conflict
// if the fcntl is issued by the same thread that earlier acquired
// this lock.
if (lockedFiles.insert(fname).second == false) {
mutex_lockedFiles.Unlock();
errno = ENOLCK;
return -1;
}
} else {
// If we are unlocking, then verify that we had locked it earlier,
// it should already exist in lockedFiles. Remove it from lockedFiles.
if (lockedFiles.erase(fname) != 1) {
mutex_lockedFiles.Unlock();
errno = ENOLCK;
return -1;
}
}
errno = 0;
struct flock f;
memset(&f, 0, sizeof(f));
f.l_type = (lock ? F_WRLCK : F_UNLCK);
f.l_whence = SEEK_SET;
f.l_start = 0;
f.l_len = 0; // Lock/unlock entire file
int value = fcntl(fd, F_SETLK, &f);
if (value == -1 && lock) {
// if there is an error in locking, then remove the pathname from lockedfiles
lockedFiles.erase(fname);
}
mutex_lockedFiles.Unlock();
return value;
}
class PosixFileLock : public FileLock {
public:
int fd_;
std::string filename;
};
class PosixEnv : public Env {
public:
PosixEnv();
virtual ~PosixEnv(){
WaitForBGThreads();
}
void SetFD_CLOEXEC(int fd, const EnvOptions* options) {
if ((options == nullptr || options->IsFDCloseOnExec()) && fd > 0) {
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
}
}
virtual Status NewSequentialFile(const std::string& fname,
unique_ptr<SequentialFile>* result,
const EnvOptions& options) {
result->reset();
FILE* f = fopen(fname.c_str(), "r");
if (f == nullptr) {
*result = nullptr;
return IOError(fname, errno);
} else {
int fd = fileno(f);
SetFD_CLOEXEC(fd, &options);
result->reset(new PosixSequentialFile(fname, f, options));
return Status::OK();
}
}
virtual Status NewRandomAccessFile(const std::string& fname,
unique_ptr<RandomAccessFile>* result,
const EnvOptions& options) {
result->reset();
Status s;
int fd = open(fname.c_str(), O_RDONLY);
SetFD_CLOEXEC(fd, &options);
if (fd < 0) {
s = IOError(fname, errno);
} else if (options.UseMmapReads() && sizeof(void*) >= 8) {
// Use of mmap for random reads has been removed because it
// kills performance when storage is fast.
// Use mmap when virtual address-space is plentiful.
uint64_t size;
s = GetFileSize(fname, &size);
if (s.ok()) {
void* base = mmap(nullptr, size, PROT_READ, MAP_SHARED, fd, 0);
if (base != MAP_FAILED) {
result->reset(new PosixMmapReadableFile(fname, base, size, options));
} else {
s = IOError(fname, errno);
}
}
close(fd);
} else {
result->reset(new PosixRandomAccessFile(fname, fd, options));
}
return s;
}
virtual Status NewWritableFile(const std::string& fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options) {
result->reset();
Status s;
const int fd = open(fname.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
if (fd < 0) {
s = IOError(fname, errno);
} else {
SetFD_CLOEXEC(fd, &options);
if (options.UseMmapWrites()) {
if (!checkedDiskForMmap_) {
// this will be executed once in the program's lifetime.
// do not use mmapWrite on non ext-3/xfs/tmpfs systems.
if (!SupportsFastAllocate(fname)) {
forceMmapOff = true;
}
checkedDiskForMmap_ = true;
}
}
if (options.UseMmapWrites() && !forceMmapOff) {
result->reset(new PosixMmapFile(fname, fd, page_size_, options));
} else {
result->reset(new PosixWritableFile(fname, fd, 65536, options));
}
}
return s;
}
virtual bool FileExists(const std::string& fname) {
return access(fname.c_str(), F_OK) == 0;
}
virtual Status GetChildren(const std::string& dir,
std::vector<std::string>* result) {
result->clear();
DIR* d = opendir(dir.c_str());
if (d == nullptr) {
return IOError(dir, errno);
}
struct dirent* entry;
while ((entry = readdir(d)) != nullptr) {
result->push_back(entry->d_name);
}
closedir(d);
return Status::OK();
}
virtual Status DeleteFile(const std::string& fname) {
Status result;
if (unlink(fname.c_str()) != 0) {
result = IOError(fname, errno);
}
return result;
};
virtual Status CreateDir(const std::string& name) {
Status result;
if (mkdir(name.c_str(), 0755) != 0) {
result = IOError(name, errno);
}
return result;
};
virtual Status CreateDirIfMissing(const std::string& name) {
Status result;
if (mkdir(name.c_str(), 0755) != 0) {
if (errno != EEXIST) {
result = IOError(name, errno);
} else if (!DirExists(name)) { // Check that name is actually a
// directory.
// Message is taken from mkdir
result = Status::IOError("`"+name+"' exists but is not a directory");
}
}
return result;
};
virtual Status DeleteDir(const std::string& name) {
Status result;
if (rmdir(name.c_str()) != 0) {
result = IOError(name, errno);
}
return result;
};
virtual Status GetFileSize(const std::string& fname, uint64_t* size) {
Status s;
struct stat sbuf;
if (stat(fname.c_str(), &sbuf) != 0) {
*size = 0;
s = IOError(fname, errno);
} else {
*size = sbuf.st_size;
}
return s;
}
virtual Status GetFileModificationTime(const std::string& fname,
uint64_t* file_mtime) {
struct stat s;
if (stat(fname.c_str(), &s) !=0) {
return IOError(fname, errno);
}
*file_mtime = static_cast<uint64_t>(s.st_mtime);
return Status::OK();
}
virtual Status RenameFile(const std::string& src, const std::string& target) {
Status result;
if (rename(src.c_str(), target.c_str()) != 0) {
result = IOError(src, errno);
}
return result;
}
virtual Status LockFile(const std::string& fname, FileLock** lock) {
*lock = nullptr;
Status result;
int fd = open(fname.c_str(), O_RDWR | O_CREAT, 0644);
if (fd < 0) {
result = IOError(fname, errno);
} else if (LockOrUnlock(fname, fd, true) == -1) {
result = IOError("lock " + fname, errno);
close(fd);
} else {
SetFD_CLOEXEC(fd, nullptr);
PosixFileLock* my_lock = new PosixFileLock;
my_lock->fd_ = fd;
my_lock->filename = fname;
*lock = my_lock;
}
return result;
}
virtual Status UnlockFile(FileLock* lock) {
PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
Status result;
if (LockOrUnlock(my_lock->filename, my_lock->fd_, false) == -1) {
result = IOError("unlock", errno);
}
close(my_lock->fd_);
delete my_lock;
return result;
}
virtual void Schedule(void (*function)(void*), void* arg);
virtual void WaitForBGThreads();
virtual void StartThread(void (*function)(void* arg), void* arg);
virtual Status GetTestDirectory(std::string* result) {
const char* env = getenv("TEST_TMPDIR");
if (env && env[0] != '\0') {
*result = env;
} else {
char buf[100];
snprintf(buf, sizeof(buf), "/tmp/leveldbtest-%d", int(geteuid()));
*result = buf;
}
// Directory may already exist
CreateDir(*result);
return Status::OK();
}
static uint64_t gettid() {
pthread_t tid = pthread_self();
uint64_t thread_id = 0;
memcpy(&thread_id, &tid, std::min(sizeof(thread_id), sizeof(tid)));
return thread_id;
}
virtual Status NewLogger(const std::string& fname,
shared_ptr<Logger>* result) {
FILE* f = fopen(fname.c_str(), "w");
if (f == nullptr) {
result->reset();
return IOError(fname, errno);
} else {
int fd = fileno(f);
SetFD_CLOEXEC(fd, nullptr);
result->reset(new PosixLogger(f, &PosixEnv::gettid));
return Status::OK();
}
}
virtual uint64_t NowMicros() {
struct timeval tv;
gettimeofday(&tv, nullptr);
return static_cast<uint64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
}
virtual void SleepForMicroseconds(int micros) {
usleep(micros);
}
virtual Status GetHostName(char* name, uint64_t len) {
int ret = gethostname(name, len);
if (ret < 0) {
if (errno == EFAULT || errno == EINVAL)
return Status::InvalidArgument(strerror(errno));
else
return IOError("GetHostName", errno);
}
return Status::OK();
}
virtual Status GetCurrentTime(int64_t* unix_time) {
time_t ret = time(nullptr);
if (ret == (time_t) -1) {
return IOError("GetCurrentTime", errno);
}
*unix_time = (int64_t) ret;
return Status::OK();
}
virtual Status GetAbsolutePath(const std::string& db_path,
std::string* output_path) {
if (db_path.find('/') == 0) {
*output_path = db_path;
return Status::OK();
}
char the_path[256];
char* ret = getcwd(the_path, 256);
if (ret == nullptr) {
return Status::IOError(strerror(errno));
}
*output_path = ret;
return Status::OK();
}
// Allow increasing the number of worker threads.
virtual void SetBackgroundThreads(int num) {
PthreadCall("lock", pthread_mutex_lock(&mu_));
if (num > num_threads_) {
num_threads_ = num;
bgthread_.resize(num_threads_);
}
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
}
virtual std::string TimeToString(uint64_t secondsSince1970) {
const time_t seconds = (time_t)secondsSince1970;
struct tm t;
int maxsize = 64;
std::string dummy;
dummy.reserve(maxsize);
dummy.resize(maxsize);
char* p = &dummy[0];
localtime_r(&seconds, &t);
snprintf(p, maxsize,
"%04d/%02d/%02d-%02d:%02d:%02d ",
t.tm_year + 1900,
t.tm_mon + 1,
t.tm_mday,
t.tm_hour,
t.tm_min,
t.tm_sec);
return dummy;
}
private:
bool checkedDiskForMmap_;
bool forceMmapOff; // do we override Env options?
void PthreadCall(const char* label, int result) {
if (result != 0) {
fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
exit(1);
}
}
// Returns true iff the named directory exists and is a directory.
virtual bool DirExists(const std::string& dname) {
struct stat statbuf;
if (stat(dname.c_str(), &statbuf) == 0) {
return S_ISDIR(statbuf.st_mode);
}
return false; // stat() failed return false
}
// BGThread() is the body of the background thread
void BGThread();
static void* BGThreadWrapper(void* arg) {
reinterpret_cast<PosixEnv*>(arg)->BGThread();
return nullptr;
}
bool SupportsFastAllocate(const std::string& path) {
struct statfs s;
if (statfs(path.c_str(), &s)){
return false;
}
switch (s.f_type) {
case EXT4_SUPER_MAGIC:
return true;
case XFS_SUPER_MAGIC:
return true;
case TMPFS_MAGIC:
return true;
default:
return false;
}
}
size_t page_size_;
pthread_mutex_t mu_;
pthread_cond_t bgsignal_;
std::vector<pthread_t> bgthread_;
int started_bgthread_;
int num_threads_;
// Entry per Schedule() call
struct BGItem { void* arg; void (*function)(void*); };
typedef std::deque<BGItem> BGQueue;
int queue_size_; // number of items in BGQueue
bool exit_all_threads_;
BGQueue queue_;
std::vector<pthread_t> threads_to_join_;
};
PosixEnv::PosixEnv() : checkedDiskForMmap_(false),
forceMmapOff(false),
page_size_(getpagesize()),
started_bgthread_(0),
num_threads_(1),
queue_size_(0),
exit_all_threads_(false) {
PthreadCall("mutex_init", pthread_mutex_init(&mu_, nullptr));
PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, nullptr));
bgthread_.resize(num_threads_);
}
// Signal and Join all background threads started by calls to Schedule
void PosixEnv::WaitForBGThreads() {
PthreadCall("lock", pthread_mutex_lock(&mu_));
assert(! exit_all_threads_);
exit_all_threads_ = true;
PthreadCall("signalall", pthread_cond_broadcast(&bgsignal_));
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
for (unsigned int i = 0; i < threads_to_join_.size(); i++) {
pthread_join(threads_to_join_[i], nullptr);
}
}
void PosixEnv::Schedule(void (*function)(void*), void* arg) {
PthreadCall("lock", pthread_mutex_lock(&mu_));
if (exit_all_threads_) {
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
return;
}
// Start background thread if necessary
for (; started_bgthread_ < num_threads_; started_bgthread_++) {
PthreadCall(
"create thread",
pthread_create(&bgthread_[started_bgthread_],
nullptr,
&PosixEnv::BGThreadWrapper,
this));
threads_to_join_.push_back(bgthread_[started_bgthread_]);
fprintf(stdout, "Created bg thread 0x%lx\n", bgthread_[started_bgthread_]);
}
// Add to priority queue
queue_.push_back(BGItem());
queue_.back().function = function;
queue_.back().arg = arg;
// always wake up at least one waiting thread.
PthreadCall("signal", pthread_cond_signal(&bgsignal_));
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
}
void PosixEnv::BGThread() {
while (true) {
// Wait until there is an item that is ready to run
PthreadCall("lock", pthread_mutex_lock(&mu_));
while (queue_.empty() && !exit_all_threads_) {
PthreadCall("wait", pthread_cond_wait(&bgsignal_, &mu_));
}
if (exit_all_threads_) { // mechanism to let BG threads exit safely
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
break;
}
void (*function)(void*) = queue_.front().function;
void* arg = queue_.front().arg;
queue_.pop_front();
PthreadCall("unlock", pthread_mutex_unlock(&mu_));
(*function)(arg);
}
}
namespace {
struct StartThreadState {
void (*user_function)(void*);
void* arg;
};
}
static void* StartThreadWrapper(void* arg) {
StartThreadState* state = reinterpret_cast<StartThreadState*>(arg);
state->user_function(state->arg);
delete state;
return nullptr;
}
void PosixEnv::StartThread(void (*function)(void* arg), void* arg) {
pthread_t t;
StartThreadState* state = new StartThreadState;
state->user_function = function;
state->arg = arg;
PthreadCall("start thread",
pthread_create(&t, nullptr, &StartThreadWrapper, state));
threads_to_join_.push_back(t);
}
} // namespace
static PosixEnv default_env;
Env* Env::Default() {
return &default_env;
}
} // namespace leveldb
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