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760 行
20 KiB
760 行
20 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include <dirent.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <pthread.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/resource.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <time.h>
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#include <unistd.h>
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#include <atomic>
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#include <cstring>
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#include <limits>
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#include <queue>
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#include <set>
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#include <thread>
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#include "leveldb/env.h"
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#include "leveldb/slice.h"
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#include "port/port.h"
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#include "port/thread_annotations.h"
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#include "util/logging.h"
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#include "util/mutexlock.h"
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#include "util/posix_logger.h"
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#include "util/env_posix_test_helper.h"
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// HAVE_FDATASYNC is defined in the auto-generated port_config.h, which is
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// included by port_stdcxx.h.
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#if !HAVE_FDATASYNC
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#define fdatasync fsync
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#endif // !HAVE_FDATASYNC
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namespace leveldb {
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namespace {
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static int open_read_only_file_limit = -1;
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static int mmap_limit = -1;
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constexpr const size_t kWritableFileBufferSize = 65536;
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static Status PosixError(const std::string& context, int err_number) {
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if (err_number == ENOENT) {
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return Status::NotFound(context, strerror(err_number));
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} else {
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return Status::IOError(context, strerror(err_number));
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}
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}
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// Helper class to limit resource usage to avoid exhaustion.
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// Currently used to limit read-only file descriptors and mmap file usage
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// so that we do not run out of file descriptors or virtual memory, or run into
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// kernel performance problems for very large databases.
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class Limiter {
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public:
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// Limit maximum number of resources to |max_acquires|.
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Limiter(int max_acquires) : acquires_allowed_(max_acquires) {}
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Limiter(const Limiter&) = delete;
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Limiter operator=(const Limiter&) = delete;
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// If another resource is available, acquire it and return true.
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// Else return false.
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bool Acquire() {
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int old_acquires_allowed =
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acquires_allowed_.fetch_sub(1, std::memory_order_relaxed);
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if (old_acquires_allowed > 0)
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return true;
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acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
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return false;
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}
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// Release a resource acquired by a previous call to Acquire() that returned
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// true.
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void Release() {
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acquires_allowed_.fetch_add(1, std::memory_order_relaxed);
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}
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private:
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// The number of available resources.
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//
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// This is a counter and is not tied to the invariants of any other class, so
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// it can be operated on safely using std::memory_order_relaxed.
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std::atomic<int> acquires_allowed_;
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};
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class PosixSequentialFile: public SequentialFile {
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private:
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std::string filename_;
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int fd_;
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public:
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PosixSequentialFile(const std::string& fname, int fd)
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: filename_(fname), fd_(fd) {}
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virtual ~PosixSequentialFile() { close(fd_); }
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virtual Status Read(size_t n, Slice* result, char* scratch) {
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Status s;
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while (true) {
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ssize_t r = read(fd_, scratch, n);
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if (r < 0) {
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if (errno == EINTR) {
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continue; // Retry
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}
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s = PosixError(filename_, errno);
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break;
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}
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*result = Slice(scratch, r);
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break;
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}
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return s;
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}
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virtual Status Skip(uint64_t n) {
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if (lseek(fd_, n, SEEK_CUR) == static_cast<off_t>(-1)) {
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return PosixError(filename_, errno);
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}
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return Status::OK();
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}
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};
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// pread() based random-access
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class PosixRandomAccessFile: public RandomAccessFile {
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private:
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std::string filename_;
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bool temporary_fd_; // If true, fd_ is -1 and we open on every read.
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int fd_;
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Limiter* limiter_;
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public:
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PosixRandomAccessFile(const std::string& fname, int fd, Limiter* limiter)
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: filename_(fname), fd_(fd), limiter_(limiter) {
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temporary_fd_ = !limiter->Acquire();
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if (temporary_fd_) {
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// Open file on every access.
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close(fd_);
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fd_ = -1;
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}
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}
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virtual ~PosixRandomAccessFile() {
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if (!temporary_fd_) {
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close(fd_);
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limiter_->Release();
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}
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}
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virtual Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const {
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int fd = fd_;
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if (temporary_fd_) {
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fd = open(filename_.c_str(), O_RDONLY);
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if (fd < 0) {
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return PosixError(filename_, errno);
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}
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}
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Status s;
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ssize_t r = pread(fd, scratch, n, static_cast<off_t>(offset));
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*result = Slice(scratch, (r < 0) ? 0 : r);
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if (r < 0) {
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// An error: return a non-ok status
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s = PosixError(filename_, errno);
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}
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if (temporary_fd_) {
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// Close the temporary file descriptor opened earlier.
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close(fd);
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}
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return s;
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}
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};
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// mmap() based random-access
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class PosixMmapReadableFile: public RandomAccessFile {
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private:
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std::string filename_;
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void* mmapped_region_;
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size_t length_;
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Limiter* limiter_;
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public:
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// base[0,length-1] contains the mmapped contents of the file.
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PosixMmapReadableFile(const std::string& fname, void* base, size_t length,
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Limiter* limiter)
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: filename_(fname), mmapped_region_(base), length_(length),
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limiter_(limiter) {
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}
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virtual ~PosixMmapReadableFile() {
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munmap(mmapped_region_, length_);
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limiter_->Release();
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}
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virtual Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const {
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Status s;
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if (offset + n > length_) {
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*result = Slice();
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s = PosixError(filename_, EINVAL);
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} else {
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*result = Slice(reinterpret_cast<char*>(mmapped_region_) + offset, n);
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}
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return s;
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}
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};
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class PosixWritableFile final : public WritableFile {
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public:
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PosixWritableFile(std::string filename, int fd)
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: pos_(0), fd_(fd), is_manifest_(IsManifest(filename)),
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filename_(std::move(filename)), dirname_(Dirname(filename_)) {}
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~PosixWritableFile() override {
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if (fd_ >= 0) {
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// Ignoring any potential errors
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Close();
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}
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}
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Status Append(const Slice& data) override {
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size_t write_size = data.size();
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const char* write_data = data.data();
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// Fit as much as possible into buffer.
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size_t copy_size = std::min(write_size, kWritableFileBufferSize - pos_);
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std::memcpy(buf_ + pos_, write_data, copy_size);
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write_data += copy_size;
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write_size -= copy_size;
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pos_ += copy_size;
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if (write_size == 0) {
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return Status::OK();
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}
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// Can't fit in buffer, so need to do at least one write.
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Status status = FlushBuffer();
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if (!status.ok()) {
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return status;
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}
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// Small writes go to buffer, large writes are written directly.
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if (write_size < kWritableFileBufferSize) {
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std::memcpy(buf_, write_data, write_size);
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pos_ = write_size;
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return Status::OK();
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}
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return WriteUnbuffered(write_data, write_size);
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}
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Status Close() override {
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Status status = FlushBuffer();
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const int close_result = ::close(fd_);
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if (close_result < 0 && status.ok()) {
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status = PosixError(filename_, errno);
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}
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fd_ = -1;
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return status;
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}
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Status Flush() override {
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return FlushBuffer();
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}
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Status Sync() override {
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// Ensure new files referred to by the manifest are in the filesystem.
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//
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// This needs to happen before the manifest file is flushed to disk, to
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// avoid crashing in a state where the manifest refers to files that are not
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// yet on disk.
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Status status = SyncDirIfManifest();
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if (!status.ok()) {
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return status;
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}
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status = FlushBuffer();
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if (status.ok() && ::fdatasync(fd_) != 0) {
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status = PosixError(filename_, errno);
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}
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return status;
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}
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private:
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Status FlushBuffer() {
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Status status = WriteUnbuffered(buf_, pos_);
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pos_ = 0;
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return status;
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}
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Status WriteUnbuffered(const char* data, size_t size) {
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while (size > 0) {
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ssize_t write_result = ::write(fd_, data, size);
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if (write_result < 0) {
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if (errno == EINTR) {
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continue; // Retry
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}
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return PosixError(filename_, errno);
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}
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data += write_result;
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size -= write_result;
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}
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return Status::OK();
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}
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Status SyncDirIfManifest() {
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Status status;
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if (!is_manifest_) {
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return status;
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}
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int fd = ::open(dirname_.c_str(), O_RDONLY);
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if (fd < 0) {
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status = PosixError(dirname_, errno);
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} else {
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if (::fsync(fd) < 0) {
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status = PosixError(dirname_, errno);
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}
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::close(fd);
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}
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return status;
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}
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// Returns the directory name in a path pointing to a file.
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//
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// Returns "." if the path does not contain any directory separator.
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static std::string Dirname(const std::string& filename) {
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std::string::size_type separator_pos = filename.rfind('/');
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if (separator_pos == std::string::npos) {
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return std::string(".");
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}
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// The filename component should not contain a path separator. If it does,
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// the splitting was done incorrectly.
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assert(filename.find('/', separator_pos + 1) == std::string::npos);
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return filename.substr(0, separator_pos);
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}
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// Extracts the file name from a path pointing to a file.
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//
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// The returned Slice points to |filename|'s data buffer, so it is only valid
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// while |filename| is alive and unchanged.
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static Slice Basename(const std::string& filename) {
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std::string::size_type separator_pos = filename.rfind('/');
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if (separator_pos == std::string::npos) {
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return Slice(filename);
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}
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// The filename component should not contain a path separator. If it does,
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// the splitting was done incorrectly.
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assert(filename.find('/', separator_pos + 1) == std::string::npos);
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return Slice(filename.data() + separator_pos + 1,
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filename.length() - separator_pos - 1);
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}
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// True if the given file is a manifest file.
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static bool IsManifest(const std::string& filename) {
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return Basename(filename).starts_with("MANIFEST");
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}
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// buf_[0, pos_ - 1] contains data to be written to fd_.
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char buf_[kWritableFileBufferSize];
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size_t pos_;
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int fd_;
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const bool is_manifest_; // True if the file's name starts with MANIFEST.
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const std::string filename_;
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const std::string dirname_; // The directory of filename_.
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};
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static int LockOrUnlock(int fd, bool lock) {
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errno = 0;
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struct flock f;
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memset(&f, 0, sizeof(f));
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f.l_type = (lock ? F_WRLCK : F_UNLCK);
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f.l_whence = SEEK_SET;
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f.l_start = 0;
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f.l_len = 0; // Lock/unlock entire file
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return fcntl(fd, F_SETLK, &f);
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}
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class PosixFileLock : public FileLock {
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public:
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int fd_;
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std::string name_;
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};
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// Set of locked files. We keep a separate set instead of just
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// relying on fcntrl(F_SETLK) since fcntl(F_SETLK) does not provide
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// any protection against multiple uses from the same process.
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class PosixLockTable {
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private:
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port::Mutex mu_;
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std::set<std::string> locked_files_ GUARDED_BY(mu_);
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public:
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bool Insert(const std::string& fname) LOCKS_EXCLUDED(mu_) {
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MutexLock l(&mu_);
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return locked_files_.insert(fname).second;
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}
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void Remove(const std::string& fname) LOCKS_EXCLUDED(mu_) {
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MutexLock l(&mu_);
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locked_files_.erase(fname);
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}
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};
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class PosixEnv : public Env {
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public:
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PosixEnv();
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virtual ~PosixEnv() {
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char msg[] = "Destroying Env::Default()\n";
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fwrite(msg, 1, sizeof(msg), stderr);
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abort();
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}
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virtual Status NewSequentialFile(const std::string& fname,
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SequentialFile** result) {
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int fd = open(fname.c_str(), O_RDONLY);
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if (fd < 0) {
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*result = nullptr;
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return PosixError(fname, errno);
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} else {
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*result = new PosixSequentialFile(fname, fd);
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return Status::OK();
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}
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}
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virtual Status NewRandomAccessFile(const std::string& fname,
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RandomAccessFile** result) {
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*result = nullptr;
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Status s;
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int fd = open(fname.c_str(), O_RDONLY);
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if (fd < 0) {
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s = PosixError(fname, errno);
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} else if (mmap_limit_.Acquire()) {
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uint64_t size;
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s = GetFileSize(fname, &size);
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if (s.ok()) {
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void* base = mmap(nullptr, size, PROT_READ, MAP_SHARED, fd, 0);
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if (base != MAP_FAILED) {
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*result = new PosixMmapReadableFile(fname, base, size, &mmap_limit_);
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} else {
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s = PosixError(fname, errno);
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}
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}
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close(fd);
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if (!s.ok()) {
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mmap_limit_.Release();
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}
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} else {
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*result = new PosixRandomAccessFile(fname, fd, &fd_limit_);
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}
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return s;
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}
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virtual Status NewWritableFile(const std::string& fname,
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WritableFile** result) {
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Status s;
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int fd = open(fname.c_str(), O_TRUNC | O_WRONLY | O_CREAT, 0644);
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if (fd < 0) {
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*result = nullptr;
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s = PosixError(fname, errno);
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} else {
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*result = new PosixWritableFile(fname, fd);
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}
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return s;
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}
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virtual Status NewAppendableFile(const std::string& fname,
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WritableFile** result) {
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Status s;
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int fd = open(fname.c_str(), O_APPEND | O_WRONLY | O_CREAT, 0644);
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if (fd < 0) {
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*result = nullptr;
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s = PosixError(fname, errno);
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} else {
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*result = new PosixWritableFile(fname, fd);
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}
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return s;
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}
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virtual bool FileExists(const std::string& fname) {
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return access(fname.c_str(), F_OK) == 0;
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}
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virtual Status GetChildren(const std::string& dir,
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std::vector<std::string>* result) {
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result->clear();
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DIR* d = opendir(dir.c_str());
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if (d == nullptr) {
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return PosixError(dir, errno);
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}
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struct dirent* entry;
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while ((entry = readdir(d)) != nullptr) {
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result->push_back(entry->d_name);
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}
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closedir(d);
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return Status::OK();
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}
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virtual Status DeleteFile(const std::string& fname) {
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Status result;
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if (unlink(fname.c_str()) != 0) {
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result = PosixError(fname, errno);
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}
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return result;
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}
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virtual Status CreateDir(const std::string& name) {
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Status result;
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if (mkdir(name.c_str(), 0755) != 0) {
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result = PosixError(name, errno);
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}
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return result;
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}
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virtual Status DeleteDir(const std::string& name) {
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Status result;
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if (rmdir(name.c_str()) != 0) {
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result = PosixError(name, errno);
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}
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return result;
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}
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virtual Status GetFileSize(const std::string& fname, uint64_t* size) {
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Status s;
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struct stat sbuf;
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if (stat(fname.c_str(), &sbuf) != 0) {
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*size = 0;
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s = PosixError(fname, errno);
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} else {
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*size = sbuf.st_size;
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}
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return s;
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}
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|
|
|
virtual Status RenameFile(const std::string& src, const std::string& target) {
|
|
Status result;
|
|
if (rename(src.c_str(), target.c_str()) != 0) {
|
|
result = PosixError(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 = PosixError(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 = PosixError("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 = PosixError("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();
|
|
}
|
|
|
|
virtual Status NewLogger(const std::string& fname, Logger** result) {
|
|
FILE* f = fopen(fname.c_str(), "w");
|
|
if (f == nullptr) {
|
|
*result = nullptr;
|
|
return PosixError(fname, errno);
|
|
} else {
|
|
*result = new PosixLogger(f);
|
|
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);
|
|
}
|
|
|
|
private:
|
|
void BackgroundThreadMain();
|
|
|
|
static void BackgroundThreadEntryPoint(PosixEnv* env) {
|
|
env->BackgroundThreadMain();
|
|
}
|
|
|
|
// Stores the work item data in a Schedule() call.
|
|
//
|
|
// Instances are constructed on the thread calling Schedule() and used on the
|
|
// background thread.
|
|
//
|
|
// This structure is thread-safe beacuse it is immutable.
|
|
struct BackgroundWorkItem {
|
|
explicit BackgroundWorkItem(void (*function)(void* arg), void* arg)
|
|
: function(function), arg(arg) {}
|
|
|
|
void (* const function)(void*);
|
|
void* const arg;
|
|
};
|
|
|
|
|
|
port::Mutex background_work_mutex_;
|
|
port::CondVar background_work_cv_ GUARDED_BY(background_work_mutex_);
|
|
bool started_background_thread_ GUARDED_BY(background_work_mutex_);
|
|
|
|
std::queue<BackgroundWorkItem> background_work_queue_
|
|
GUARDED_BY(background_work_mutex_);
|
|
|
|
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()
|
|
: background_work_cv_(&background_work_mutex_),
|
|
started_background_thread_(false),
|
|
mmap_limit_(MaxMmaps()),
|
|
fd_limit_(MaxOpenFiles()) {
|
|
}
|
|
|
|
void PosixEnv::Schedule(
|
|
void (*background_work_function)(void* background_work_arg),
|
|
void* background_work_arg) {
|
|
MutexLock lock(&background_work_mutex_);
|
|
|
|
// Start the background thread, if we haven't done so already.
|
|
if (!started_background_thread_) {
|
|
started_background_thread_ = true;
|
|
std::thread background_thread(PosixEnv::BackgroundThreadEntryPoint, this);
|
|
background_thread.detach();
|
|
}
|
|
|
|
// If the queue is empty, the background thread may be waiting for work.
|
|
if (background_work_queue_.empty()) {
|
|
background_work_cv_.Signal();
|
|
}
|
|
|
|
background_work_queue_.emplace(background_work_function, background_work_arg);
|
|
}
|
|
|
|
void PosixEnv::BackgroundThreadMain() {
|
|
while (true) {
|
|
background_work_mutex_.Lock();
|
|
|
|
// Wait until there is work to be done.
|
|
while (background_work_queue_.empty()) {
|
|
background_work_cv_.Wait();
|
|
}
|
|
|
|
assert(!background_work_queue_.empty());
|
|
auto background_work_function =
|
|
background_work_queue_.front().function;
|
|
void* background_work_arg = background_work_queue_.front().arg;
|
|
background_work_queue_.pop();
|
|
|
|
background_work_mutex_.Unlock();
|
|
background_work_function(background_work_arg);
|
|
}
|
|
}
|
|
|
|
} // namespace
|
|
|
|
void PosixEnv::StartThread(void (*thread_main)(void* thread_main_arg),
|
|
void* thread_main_arg) {
|
|
std::thread new_thread(thread_main, thread_main_arg);
|
|
new_thread.detach();
|
|
}
|
|
|
|
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 == nullptr);
|
|
open_read_only_file_limit = limit;
|
|
}
|
|
|
|
void EnvPosixTestHelper::SetReadOnlyMMapLimit(int limit) {
|
|
assert(default_env == nullptr);
|
|
mmap_limit = limit;
|
|
}
|
|
|
|
Env* Env::Default() {
|
|
pthread_once(&once, InitDefaultEnv);
|
|
return default_env;
|
|
}
|
|
|
|
} // namespace leveldb
|