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LevelDB-course-Lab/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/mman.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#if defined(LEVELDB_PLATFORM_ANDROID)
#include <sys/stat.h>
#endif
#include "leveldb/env.h"
#include "leveldb/slice.h"
#include "port/port.h"
#include "util/logging.h"
#include "util/mutexlock.h"
#include "util/posix_logger.h"
namespace leveldb {
namespace {
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_;
public:
PosixSequentialFile(const std::string& fname, FILE* f)
: filename_(fname), file_(f) { }
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);
}
}
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_;
public:
PosixRandomAccessFile(const std::string& fname, int fd)
: filename_(fname), fd_(fd) { }
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);
}
return s;
}
};
// Helper class to limit mmap file usage so that we do not end up
// running out virtual memory or running into kernel performance
// problems for very large databases.
class MmapLimiter {
public:
// Up to 1000 mmaps for 64-bit binaries; none for smaller pointer sizes.
MmapLimiter() {
SetAllowed(sizeof(void*) >= 8 ? 1000 : 0);
}
// If another mmap slot is available, acquire it and return true.
// Else return false.
bool Acquire() {
if (GetAllowed() <= 0) {
return false;
}
MutexLock l(&mu_);
intptr_t x = GetAllowed();
if (x <= 0) {
return false;
} else {
SetAllowed(x - 1);
return true;
}
}
// Release a slot acquired by a previous call to Acquire() that returned true.
void Release() {
MutexLock l(&mu_);
SetAllowed(GetAllowed() + 1);
}
private:
port::Mutex mu_;
port::AtomicPointer allowed_;
intptr_t GetAllowed() const {
return reinterpret_cast<intptr_t>(allowed_.Acquire_Load());
}
// REQUIRES: mu_ must be held
void SetAllowed(intptr_t v) {
allowed_.Release_Store(reinterpret_cast<void*>(v));
}
MmapLimiter(const MmapLimiter&);
void operator=(const MmapLimiter&);
};
// mmap() based random-access
class PosixMmapReadableFile: public RandomAccessFile {
private:
std::string filename_;
void* mmapped_region_;
size_t length_;
MmapLimiter* limiter_;
public:
// base[0,length-1] contains the mmapped contents of the file.
PosixMmapReadableFile(const std::string& fname, void* base, size_t length,
MmapLimiter* limiter)
: filename_(fname), mmapped_region_(base), length_(length),
limiter_(limiter) {
}
virtual ~PosixMmapReadableFile() {
munmap(mmapped_region_, length_);
limiter_->Release();
}
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_ != NULL) {
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_ = NULL;
limit_ = NULL;
last_sync_ = NULL;
dst_ = NULL;
// Increase the amount we map the next time, but capped at 1MB
if (map_size_ < (1<<20)) {
map_size_ *= 2;
}
}
return result;
}
bool MapNewRegion() {
assert(base_ == NULL);
if (ftruncate(fd_, file_offset_ + map_size_) < 0) {
return false;
}
void* ptr = mmap(NULL, map_size_, PROT_READ | PROT_WRITE, MAP_SHARED,
fd_, file_offset_);
if (ptr == MAP_FAILED) {
return false;
}
base_ = reinterpret_cast<char*>(ptr);
limit_ = base_ + map_size_;
dst_ = base_;
last_sync_ = base_;
return true;
}
public:
PosixMmapFile(const std::string& fname, int fd, size_t page_size)
: filename_(fname),
fd_(fd),
page_size_(page_size),
map_size_(Roundup(65536, page_size)),
base_(NULL),
limit_(NULL),
dst_(NULL),
last_sync_(NULL),
file_offset_(0),
pending_sync_(false) {
assert((page_size & (page_size - 1)) == 0);
}
~PosixMmapFile() {
if (fd_ >= 0) {
PosixMmapFile::Close();
}
}
virtual Status Append(const Slice& data) {
const char* src = data.data();
size_t left = data.size();
while (left > 0) {
assert(base_ <= dst_);
assert(dst_ <= limit_);
size_t avail = limit_ - dst_;
if (avail == 0) {
if (!UnmapCurrentRegion() ||
!MapNewRegion()) {
return IOError(filename_, errno);
}
}
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_ = NULL;
limit_ = NULL;
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;
}
};
static int LockOrUnlock(int fd, bool lock) {
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
return fcntl(fd, F_SETLK, &f);
}
class PosixFileLock : public FileLock {
public:
int fd_;
std::string name_;
};
// Set of locked files. We keep a separate set instead of just
// relying on fcntrl(F_SETLK) since fcntl(F_SETLK) does not provide
// any protection against multiple uses from the same process.
class PosixLockTable {
private:
port::Mutex mu_;
std::set<std::string> locked_files_;
public:
bool Insert(const std::string& fname) {
MutexLock l(&mu_);
return locked_files_.insert(fname).second;
}
void Remove(const std::string& fname) {
MutexLock l(&mu_);
locked_files_.erase(fname);
}
};
class PosixEnv : public Env {
public:
PosixEnv();
virtual ~PosixEnv() {
fprintf(stderr, "Destroying Env::Default()\n");
abort();
}
virtual Status NewSequentialFile(const std::string& fname,
SequentialFile** result) {
FILE* f = fopen(fname.c_str(), "r");
if (f == NULL) {
*result = NULL;
return IOError(fname, errno);
} else {
*result = new PosixSequentialFile(fname, f);
return Status::OK();
}
}
virtual Status NewRandomAccessFile(const std::string& fname,
RandomAccessFile** result) {
*result = NULL;
Status s;
int fd = open(fname.c_str(), O_RDONLY);
if (fd < 0) {
s = IOError(fname, errno);
} else if (mmap_limit_.Acquire()) {
uint64_t size;
s = GetFileSize(fname, &size);
if (s.ok()) {
void* base = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
if (base != MAP_FAILED) {
*result = new PosixMmapReadableFile(fname, base, size, &mmap_limit_);
} else {
s = IOError(fname, errno);
}
}
close(fd);
if (!s.ok()) {
mmap_limit_.Release();
}
} else {
*result = new PosixRandomAccessFile(fname, fd);
}
return s;
}
virtual Status NewWritableFile(const std::string& fname,
WritableFile** result) {
Status s;
const int fd = open(fname.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
if (fd < 0) {
*result = NULL;
s = IOError(fname, errno);
} else {
*result = new PosixMmapFile(fname, fd, page_size_);
}
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 == NULL) {
return IOError(dir, errno);
}
struct dirent* entry;
while ((entry = readdir(d)) != NULL) {
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 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 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 = NULL;
Status result;
int fd = open(fname.c_str(), O_RDWR | O_CREAT, 0644);
if (fd < 0) {
result = IOError(fname, errno);
} else if (!locks_.Insert(fname)) {
close(fd);
result = Status::IOError("lock " + fname, "already held by process");
} else if (LockOrUnlock(fd, true) == -1) {
result = IOError("lock " + fname, errno);
close(fd);
locks_.Remove(fname);
} else {
PosixFileLock* my_lock = new PosixFileLock;
my_lock->fd_ = fd;
my_lock->name_ = fname;
*lock = my_lock;
}
return result;
}
virtual Status UnlockFile(FileLock* lock) {
PosixFileLock* my_lock = reinterpret_cast<PosixFileLock*>(lock);
Status result;
if (LockOrUnlock(my_lock->fd_, false) == -1) {
result = IOError("unlock", errno);
}
locks_.Remove(my_lock->name_);
close(my_lock->fd_);
delete my_lock;
return result;
}
virtual void Schedule(void (*function)(void*), void* arg);
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, Logger** result) {
FILE* f = fopen(fname.c_str(), "w");
if (f == NULL) {
*result = NULL;
return IOError(fname, errno);
} else {
*result = new PosixLogger(f, &PosixEnv::gettid);
return Status::OK();
}
}
virtual uint64_t NowMicros() {
struct timeval tv;
gettimeofday(&tv, NULL);
return static_cast<uint64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
}
virtual void SleepForMicroseconds(int micros) {
usleep(micros);
}
private:
void PthreadCall(const char* label, int result) {
if (result != 0) {
fprintf(stderr, "pthread %s: %s\n", label, strerror(result));
abort();
}
}
// BGThread() is the body of the background thread
void BGThread();
static void* BGThreadWrapper(void* arg) {
reinterpret_cast<PosixEnv*>(arg)->BGThread();
return NULL;
}
size_t page_size_;
pthread_mutex_t mu_;
pthread_cond_t bgsignal_;
pthread_t bgthread_;
bool started_bgthread_;
// Entry per Schedule() call
struct BGItem { void* arg; void (*function)(void*); };
typedef std::deque<BGItem> BGQueue;
BGQueue queue_;
PosixLockTable locks_;
MmapLimiter mmap_limit_;
};
PosixEnv::PosixEnv() : page_size_(getpagesize()),
started_bgthread_(false) {
PthreadCall("mutex_init", pthread_mutex_init(&mu_, NULL));
PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, NULL));
}
void PosixEnv::Schedule(void (*function)(void*), void* arg) {
PthreadCall("lock", pthread_mutex_lock(&mu_));
// Start background thread if necessary
if (!started_bgthread_) {
started_bgthread_ = true;
PthreadCall(
"create thread",
pthread_create(&bgthread_, NULL, &PosixEnv::BGThreadWrapper, this));
}
// If the queue is currently empty, the background thread may currently be
// waiting.
if (queue_.empty()) {
PthreadCall("signal", pthread_cond_signal(&bgsignal_));
}
// Add to priority queue
queue_.push_back(BGItem());
queue_.back().function = function;
queue_.back().arg = arg;
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()) {
PthreadCall("wait", pthread_cond_wait(&bgsignal_, &mu_));
}
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 NULL;
}
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, NULL, &StartThreadWrapper, state));
}
} // namespace
static pthread_once_t once = PTHREAD_ONCE_INIT;
static Env* default_env;
static void InitDefaultEnv() { default_env = new PosixEnv; }
Env* Env::Default() {
pthread_once(&once, InitDefaultEnv);
return default_env;
}
} // namespace leveldb