Improve durability of schema version file writes
- call close explicitly in writeFile to prevent the close exception from being ignored - fsync after writing schema file to flush data to disk - fsync schema file parent to flush metadata to disk https://github.com/NixOS/nix/issues/7064
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@ -158,7 +158,7 @@ void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd)
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txn.commit();
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}
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writeFile(schemaPath, fmt("%d", nixCASchemaVersion));
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writeFile(schemaPath, fmt("%d", nixCASchemaVersion), 0666, true);
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lockFile(lockFd.get(), ltRead, true);
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}
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}
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@ -281,7 +281,7 @@ LocalStore::LocalStore(const Params & params)
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else if (curSchema == 0) { /* new store */
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curSchema = nixSchemaVersion;
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openDB(*state, true);
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writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
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writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str(), 0666, true);
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}
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else if (curSchema < nixSchemaVersion) {
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@ -329,7 +329,7 @@ LocalStore::LocalStore(const Params & params)
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txn.commit();
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}
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writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
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writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str(), 0666, true);
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lockFile(globalLock.get(), ltRead, true);
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}
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@ -353,7 +353,7 @@ void readFile(const Path & path, Sink & sink)
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}
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void writeFile(const Path & path, std::string_view s, mode_t mode)
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void writeFile(const Path & path, std::string_view s, mode_t mode, bool sync)
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{
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AutoCloseFD fd = open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
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if (!fd)
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@ -364,10 +364,16 @@ void writeFile(const Path & path, std::string_view s, mode_t mode)
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e.addTrace({}, "writing file '%1%'", path);
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throw;
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}
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if (sync)
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fd.fsync();
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// Explicitly close to make sure exceptions are propagated.
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fd.close();
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if (sync)
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syncParent(path);
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}
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void writeFile(const Path & path, Source & source, mode_t mode)
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void writeFile(const Path & path, Source & source, mode_t mode, bool sync)
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{
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AutoCloseFD fd = open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
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if (!fd)
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@ -386,6 +392,20 @@ void writeFile(const Path & path, Source & source, mode_t mode)
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e.addTrace({}, "writing file '%1%'", path);
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throw;
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}
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if (sync)
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fd.fsync();
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// Explicitly close to make sure exceptions are propagated.
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fd.close();
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if (sync)
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syncParent(path);
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}
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void syncParent(const Path & path)
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{
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AutoCloseFD fd = open(dirOf(path).c_str(), O_RDONLY, 0);
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if (!fd)
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throw SysError("opening file '%1%'", path);
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fd.fsync();
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}
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std::string readLine(int fd)
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@ -841,6 +861,20 @@ void AutoCloseFD::close()
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}
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}
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void AutoCloseFD::fsync()
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{
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if (fd != -1) {
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int result;
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#if __APPLE__
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result = ::fcntl(fd, F_FULLFSYNC);
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#else
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result = ::fsync(fd);
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#endif
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if (result == -1)
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throw SysError("fsync file descriptor %1%", fd);
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}
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}
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AutoCloseFD::operator bool() const
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{
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@ -115,9 +115,12 @@ std::string readFile(const Path & path);
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void readFile(const Path & path, Sink & sink);
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/* Write a string to a file. */
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void writeFile(const Path & path, std::string_view s, mode_t mode = 0666);
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void writeFile(const Path & path, std::string_view s, mode_t mode = 0666, bool sync = false);
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void writeFile(const Path & path, Source & source, mode_t mode = 0666);
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void writeFile(const Path & path, Source & source, mode_t mode = 0666, bool sync = false);
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/* Flush a file's parent directory to disk */
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void syncParent(const Path & path);
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/* Read a line from a file descriptor. */
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std::string readLine(int fd);
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@ -231,6 +234,7 @@ public:
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explicit operator bool() const;
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int release();
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void close();
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void fsync();
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};
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