Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
tree: 946e5b5a4c
Fetching contributors…

Octocat-spinner-32-eaf2f5

Cannot retrieve contributors at this time

file 699 lines (613 sloc) 17.999 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
// 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");
    exit(1);
  }

  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));
      exit(1);
    }
  }

  // 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
Something went wrong with that request. Please try again.