| //===-Caching.cpp - LLVM Local File Cache ---------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the localCache function, which simplifies creating, |
| // adding to, and querying a local file system cache. localCache takes care of |
| // periodically pruning older files from the cache using a CachePruningPolicy. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Support/Caching.h" |
| #include "llvm/Support/Errc.h" |
| #include "llvm/Support/FileSystem.h" |
| #include "llvm/Support/MemoryBuffer.h" |
| #include "llvm/Support/Path.h" |
| |
| #if !defined(_MSC_VER) && !defined(__MINGW32__) |
| #include <unistd.h> |
| #else |
| #include <io.h> |
| #endif |
| |
| using namespace llvm; |
| |
| Expected<FileCache> llvm::localCache(const Twine &CacheNameRef, |
| const Twine &TempFilePrefixRef, |
| const Twine &CacheDirectoryPathRef, |
| AddBufferFn AddBuffer) { |
| |
| // Create local copies which are safely captured-by-copy in lambdas |
| SmallString<64> CacheName, TempFilePrefix, CacheDirectoryPath; |
| CacheNameRef.toVector(CacheName); |
| TempFilePrefixRef.toVector(TempFilePrefix); |
| CacheDirectoryPathRef.toVector(CacheDirectoryPath); |
| |
| return [=](unsigned Task, StringRef Key, |
| const Twine &ModuleName) -> Expected<AddStreamFn> { |
| // This choice of file name allows the cache to be pruned (see pruneCache() |
| // in include/llvm/Support/CachePruning.h). |
| SmallString<64> EntryPath; |
| sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key); |
| // First, see if we have a cache hit. |
| SmallString<64> ResultPath; |
| Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead( |
| Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath); |
| std::error_code EC; |
| if (FDOrErr) { |
| ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = |
| MemoryBuffer::getOpenFile(*FDOrErr, EntryPath, |
| /*FileSize=*/-1, |
| /*RequiresNullTerminator=*/false); |
| sys::fs::closeFile(*FDOrErr); |
| if (MBOrErr) { |
| AddBuffer(Task, ModuleName, std::move(*MBOrErr)); |
| return AddStreamFn(); |
| } |
| EC = MBOrErr.getError(); |
| } else { |
| EC = errorToErrorCode(FDOrErr.takeError()); |
| } |
| |
| // On Windows we can fail to open a cache file with a permission denied |
| // error. This generally means that another process has requested to delete |
| // the file while it is still open, but it could also mean that another |
| // process has opened the file without the sharing permissions we need. |
| // Since the file is probably being deleted we handle it in the same way as |
| // if the file did not exist at all. |
| if (EC != errc::no_such_file_or_directory && EC != errc::permission_denied) |
| return createStringError(EC, Twine("Failed to open cache file ") + |
| EntryPath + ": " + EC.message() + "\n"); |
| |
| // This file stream is responsible for commiting the resulting file to the |
| // cache and calling AddBuffer to add it to the link. |
| struct CacheStream : CachedFileStream { |
| AddBufferFn AddBuffer; |
| sys::fs::TempFile TempFile; |
| std::string ModuleName; |
| unsigned Task; |
| |
| CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer, |
| sys::fs::TempFile TempFile, std::string EntryPath, |
| std::string ModuleName, unsigned Task) |
| : CachedFileStream(std::move(OS), std::move(EntryPath)), |
| AddBuffer(std::move(AddBuffer)), TempFile(std::move(TempFile)), |
| ModuleName(ModuleName), Task(Task) {} |
| |
| ~CacheStream() { |
| // TODO: Manually commit rather than using non-trivial destructor, |
| // allowing to replace report_fatal_errors with a return Error. |
| |
| // Make sure the stream is closed before committing it. |
| OS.reset(); |
| |
| // Open the file first to avoid racing with a cache pruner. |
| ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = |
| MemoryBuffer::getOpenFile( |
| sys::fs::convertFDToNativeFile(TempFile.FD), ObjectPathName, |
| /*FileSize=*/-1, /*RequiresNullTerminator=*/false); |
| if (!MBOrErr) |
| report_fatal_error(Twine("Failed to open new cache file ") + |
| TempFile.TmpName + ": " + |
| MBOrErr.getError().message() + "\n"); |
| |
| // On POSIX systems, this will atomically replace the destination if |
| // it already exists. We try to emulate this on Windows, but this may |
| // fail with a permission denied error (for example, if the destination |
| // is currently opened by another process that does not give us the |
| // sharing permissions we need). Since the existing file should be |
| // semantically equivalent to the one we are trying to write, we give |
| // AddBuffer a copy of the bytes we wrote in that case. We do this |
| // instead of just using the existing file, because the pruner might |
| // delete the file before we get a chance to use it. |
| Error E = TempFile.keep(ObjectPathName); |
| E = handleErrors(std::move(E), [&](const ECError &E) -> Error { |
| std::error_code EC = E.convertToErrorCode(); |
| if (EC != errc::permission_denied) |
| return errorCodeToError(EC); |
| |
| auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(), |
| ObjectPathName); |
| MBOrErr = std::move(MBCopy); |
| |
| // FIXME: should we consume the discard error? |
| consumeError(TempFile.discard()); |
| |
| return Error::success(); |
| }); |
| |
| if (E) |
| report_fatal_error(Twine("Failed to rename temporary file ") + |
| TempFile.TmpName + " to " + ObjectPathName + ": " + |
| toString(std::move(E)) + "\n"); |
| |
| AddBuffer(Task, ModuleName, std::move(*MBOrErr)); |
| } |
| }; |
| |
| return [=](size_t Task, const Twine &ModuleName) |
| -> Expected<std::unique_ptr<CachedFileStream>> { |
| // Create the cache directory if not already done. Doing this lazily |
| // ensures the filesystem isn't mutated until the cache is. |
| if (std::error_code EC = sys::fs::create_directories( |
| CacheDirectoryPath, /*IgnoreExisting=*/true)) |
| return errorCodeToError(EC); |
| |
| // Write to a temporary to avoid race condition |
| SmallString<64> TempFilenameModel; |
| sys::path::append(TempFilenameModel, CacheDirectoryPath, |
| TempFilePrefix + "-%%%%%%.tmp.o"); |
| Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create( |
| TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write); |
| if (!Temp) |
| return createStringError(errc::io_error, |
| toString(Temp.takeError()) + ": " + CacheName + |
| ": Can't get a temporary file"); |
| |
| // This CacheStream will move the temporary file into the cache when done. |
| return std::make_unique<CacheStream>( |
| std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false), |
| AddBuffer, std::move(*Temp), std::string(EntryPath.str()), |
| ModuleName.str(), Task); |
| }; |
| }; |
| } |