r1

src/leveldb/util/env_posix.cc

@@ -0,0 +1,706 @@
+// 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.
+#if !defined(LEVELDB_PLATFORM_WINDOWS)
+
+#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/resource.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+#include <deque>
+#include <limits>
+#include <set>
+#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"
+#include "util/env_posix_test_helper.h"
+
+namespace leveldb {
+
+namespace {
+
+static int open_read_only_file_limit = -1;
+static int mmap_limit = -1;
+
+static Status IOError(const std::string& context, int err_number) {
+  return Status::IOError(context, strerror(err_number));
+}
+
+// Helper class to limit resource usage to avoid exhaustion.
+// Currently used to limit read-only file descriptors and mmap file usage
+// so that we do not end up running out of file descriptors, virtual memory,
+// or running into kernel performance problems for very large databases.
+class Limiter {
+ public:
+  // Limit maximum number of resources to |n|.
+  Limiter(intptr_t n) {
+    SetAllowed(n);
+  }
+
+  // If another resource 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 resource 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));
+  }
+
+  Limiter(const Limiter&);
+  void operator=(const Limiter&);
+};
+
+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();
+  }
+
+  virtual std::string GetName() const { return filename_; }
+};
+
+// pread() based random-access
+class PosixRandomAccessFile: public RandomAccessFile {
+ private:
+  std::string filename_;
+  bool temporary_fd_;  // If true, fd_ is -1 and we open on every read.
+  int fd_;
+  Limiter* limiter_;
+
+ public:
+  PosixRandomAccessFile(const std::string& fname, int fd, Limiter* limiter)
+      : filename_(fname), fd_(fd), limiter_(limiter) {
+    temporary_fd_ = !limiter->Acquire();
+    if (temporary_fd_) {
+      // Open file on every access.
+      close(fd_);
+      fd_ = -1;
+    }
+  }
+
+  virtual ~PosixRandomAccessFile() {
+    if (!temporary_fd_) {
+      close(fd_);
+      limiter_->Release();
+    }
+  }
+
+  virtual Status Read(uint64_t offset, size_t n, Slice* result,
+                      char* scratch) const {
+    int fd = fd_;
+    if (temporary_fd_) {
+      fd = open(filename_.c_str(), O_RDONLY);
+      if (fd < 0) {
+        return IOError(filename_, errno);
+      }
+    }
+
+    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 (temporary_fd_) {
+      // Close the temporary file descriptor opened earlier.
+      close(fd);
+    }
+    return s;
+  }
+
+  virtual std::string GetName() const { return filename_; }
+};
+
+// mmap() based random-access
+class PosixMmapReadableFile: public RandomAccessFile {
+ private:
+  std::string filename_;
+  void* mmapped_region_;
+  size_t length_;
+  Limiter* limiter_;
+
+ public:
+  // base[0,length-1] contains the mmapped contents of the file.
+  PosixMmapReadableFile(const std::string& fname, void* base, size_t length,
+                        Limiter* 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;
+  }
+
+  virtual std::string GetName() const { return filename_; }
+};
+
+class PosixWritableFile : public WritableFile {
+ private:
+  std::string filename_;
+  FILE* file_;
+
+ public:
+  PosixWritableFile(const std::string& fname, FILE* f)
+      : filename_(fname), file_(f) { }
+
+  ~PosixWritableFile() {
+    if (file_ != NULL) {
+      // Ignoring any potential errors
+      fclose(file_);
+    }
+  }
+
+  virtual Status Append(const Slice& data) {
+    size_t r = fwrite_unlocked(data.data(), 1, data.size(), file_);
+    if (r != data.size()) {
+      return IOError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+  virtual Status Close() {
+    Status result;
+    if (fclose(file_) != 0) {
+      result = IOError(filename_, errno);
+    }
+    file_ = NULL;
+    return result;
+  }
+
+  virtual Status Flush() {
+    if (fflush_unlocked(file_) != 0) {
+      return IOError(filename_, errno);
+    }
+    return Status::OK();
+  }
+
+  Status SyncDirIfManifest() {
+    const char* f = filename_.c_str();
+    const char* sep = strrchr(f, '/');
+    Slice basename;
+    std::string dir;
+    if (sep == NULL) {
+      dir = ".";
+      basename = f;
+    } else {
+      dir = std::string(f, sep - f);
+      basename = sep + 1;
+    }
+    Status s;
+    if (basename.starts_with("MANIFEST")) {
+      int fd = open(dir.c_str(), O_RDONLY);
+      if (fd < 0) {
+        s = IOError(dir, errno);
+      } else {
+        if (fsync(fd) < 0 && errno != EINVAL) {
+          s = IOError(dir, errno);
+        }
+        close(fd);
+      }
+    }
+    return s;
+  }
+
+  virtual Status Sync() {
+    // Ensure new files referred to by the manifest are in the filesystem.
+    Status s = SyncDirIfManifest();
+    if (!s.ok()) {
+      return s;
+    }
+    if (fflush_unlocked(file_) != 0 ||
+        fdatasync(fileno(file_)) != 0) {
+      s = Status::IOError(filename_, strerror(errno));
+    }
+    return s;
+  }
+
+  virtual std::string GetName() const { return filename_; }
+};
+
+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() {
+    char msg[] = "Destroying Env::Default()\n";
+    fwrite(msg, 1, sizeof(msg), stderr);
+    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, &fd_limit_);
+    }
+    return s;
+  }
+
+  virtual Status NewWritableFile(const std::string& fname,
+                                 WritableFile** result) {
+    Status s;
+    FILE* f = fopen(fname.c_str(), "w");
+    if (f == NULL) {
+      *result = NULL;
+      s = IOError(fname, errno);
+    } else {
+      *result = new PosixWritableFile(fname, f);
+    }
+    return s;
+  }
+
+  virtual Status NewAppendableFile(const std::string& fname,
+                                   WritableFile** result) {
+    Status s;
+    FILE* f = fopen(fname.c_str(), "a");
+    if (f == NULL) {
+      *result = NULL;
+      s = IOError(fname, errno);
+    } else {
+      *result = new PosixWritableFile(fname, f);
+    }
+    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;
+  }
+
+  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_;
+  Limiter mmap_limit_;
+  Limiter fd_limit_;
+};
+
+// Return the maximum number of concurrent mmaps.
+static int MaxMmaps() {
+  if (mmap_limit >= 0) {
+    return mmap_limit;
+  }
+  // Up to 1000 mmaps for 64-bit binaries; none for smaller pointer sizes.
+  mmap_limit = sizeof(void*) >= 8 ? 1000 : 0;
+  return mmap_limit;
+}
+
+// Return the maximum number of read-only files to keep open.
+static intptr_t MaxOpenFiles() {
+  if (open_read_only_file_limit >= 0) {
+    return open_read_only_file_limit;
+  }
+  struct rlimit rlim;
+  if (getrlimit(RLIMIT_NOFILE, &rlim)) {
+    // getrlimit failed, fallback to hard-coded default.
+    open_read_only_file_limit = 50;
+  } else if (rlim.rlim_cur == RLIM_INFINITY) {
+    open_read_only_file_limit = std::numeric_limits<int>::max();
+  } else {
+    // Allow use of 20% of available file descriptors for read-only files.
+    open_read_only_file_limit = rlim.rlim_cur / 5;
+  }
+  return open_read_only_file_limit;
+}
+
+PosixEnv::PosixEnv()
+    : started_bgthread_(false),
+      mmap_limit_(MaxMmaps()),
+      fd_limit_(MaxOpenFiles()) {
+  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; }
+
+void EnvPosixTestHelper::SetReadOnlyFDLimit(int limit) {
+  assert(default_env == NULL);
+  open_read_only_file_limit = limit;
+}
+
+void EnvPosixTestHelper::SetReadOnlyMMapLimit(int limit) {
+  assert(default_env == NULL);
+  mmap_limit = limit;
+}
+
+Env* Env::Default() {
+  pthread_once(&once, InitDefaultEnv);
+  return default_env;
+}
+
+}  // namespace leveldb
+
+#endif