env: add ReuseWritableFile

Add an environment method to reuse an existing file.  Provide a generic
implementation that does a simple rename + open (writeable), and also a
posix variant that is more careful about error handling (if we fail to
open, do not rename, etc.).

Signed-off-by: Sage Weil <sage@redhat.com>
main
Sage Weil 9 years ago
parent e1a09a7703
commit 1bcafb62f4
  1. 6
      include/rocksdb/env.h
  2. 11
      util/env.cc
  3. 44
      util/env_posix.cc

@ -139,6 +139,12 @@ class Env {
unique_ptr<WritableFile>* result,
const EnvOptions& options) = 0;
// Reuse an existing file by renaming it and opening it as writable.
virtual Status ReuseWritableFile(const std::string& fname,
const std::string& old_fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options);
// Create an object that represents a directory. Will fail if directory
// doesn't exist. If the directory exists, it will open the directory
// and create a new Directory object.

@ -27,6 +27,17 @@ uint64_t Env::GetThreadID() const {
return hasher(std::this_thread::get_id());
}
Status Env::ReuseWritableFile(const std::string& fname,
const std::string& old_fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options) {
Status s = RenameFile(old_fname, fname);
if (!s.ok()) {
return s;
}
return NewWritableFile(fname, result, options);
}
SequentialFile::~SequentialFile() {
}

@ -933,6 +933,50 @@ class PosixEnv : public Env {
return s;
}
virtual Status ReuseWritableFile(const std::string& fname,
const std::string& old_fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options) override {
result->reset();
Status s;
int fd = -1;
do {
IOSTATS_TIMER_GUARD(open_nanos);
fd = open(old_fname.c_str(), O_RDWR, 0644);
} while (fd < 0 && errno == EINTR);
if (fd < 0) {
s = IOError(fname, errno);
} else {
SetFD_CLOEXEC(fd, &options);
// rename into place
if (rename(old_fname.c_str(), fname.c_str()) != 0) {
Status r = IOError(old_fname, errno);
close(fd);
return r;
}
if (options.use_mmap_writes) {
if (!checkedDiskForMmap_) {
// this will be executed once in the program's lifetime.
// do not use mmapWrite on non ext-3/xfs/tmpfs systems.
if (!SupportsFastAllocate(fname)) {
forceMmapOff = true;
}
checkedDiskForMmap_ = true;
}
}
if (options.use_mmap_writes && !forceMmapOff) {
result->reset(new PosixMmapFile(fname, fd, page_size_, options));
} else {
// disable mmap writes
EnvOptions no_mmap_writes_options = options;
no_mmap_writes_options.use_mmap_writes = false;
result->reset(new PosixWritableFile(fname, fd, no_mmap_writes_options));
}
}
return s;
}
virtual Status NewDirectory(const std::string& name,
unique_ptr<Directory>* result) override {
result->reset();

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