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//===- OnDiskCommon.cpp ---------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "OnDiskCommon.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Process.h"
#include <limits>
#include <mutex>
#include <optional>
#include <thread>
#if __has_include(<sys/file.h>)
#include <sys/file.h>
#ifdef LOCK_SH
#define HAVE_FLOCK 1
#else
#define HAVE_FLOCK 0
#endif
#endif
#if __has_include(<fcntl.h>)
#include <fcntl.h>
#endif
using namespace llvm;
static uint64_t OnDiskCASMaxMappingSize = 0;
Expected<std::optional<uint64_t>> cas::ondisk::getOverriddenMaxMappingSize() {
static std::once_flag Flag;
Error Err = Error::success();
std::call_once(Flag, [&Err] {
ErrorAsOutParameter EAO(&Err);
constexpr const char *EnvVar = "LLVM_CAS_MAX_MAPPING_SIZE";
auto Value = sys::Process::GetEnv(EnvVar);
if (!Value)
return;
uint64_t Size;
if (StringRef(*Value).getAsInteger(/*auto*/ 0, Size))
Err = createStringError(inconvertibleErrorCode(),
"invalid value for %s: expected integer", EnvVar);
OnDiskCASMaxMappingSize = Size;
});
if (Err)
return std::move(Err);
if (OnDiskCASMaxMappingSize == 0)
return std::nullopt;
return OnDiskCASMaxMappingSize;
}
void cas::ondisk::setMaxMappingSize(uint64_t Size) {
OnDiskCASMaxMappingSize = Size;
}
std::error_code cas::ondisk::lockFileThreadSafe(int FD, bool Exclusive) {
#if HAVE_FLOCK
if (flock(FD, Exclusive ? LOCK_EX : LOCK_SH) == 0)
return std::error_code();
return std::error_code(errno, std::generic_category());
#elif defined(_WIN32)
// On Windows this implementation is thread-safe.
return sys::fs::lockFile(FD, Exclusive);
#else
return make_error_code(std::errc::no_lock_available);
#endif
}
std::error_code cas::ondisk::unlockFileThreadSafe(int FD) {
#if HAVE_FLOCK
if (flock(FD, LOCK_UN) == 0)
return std::error_code();
return std::error_code(errno, std::generic_category());
#elif defined(_WIN32)
// On Windows this implementation is thread-safe.
return sys::fs::unlockFile(FD);
#else
return make_error_code(std::errc::no_lock_available);
#endif
}
std::error_code
cas::ondisk::tryLockFileThreadSafe(int FD, std::chrono::milliseconds Timeout,
bool Exclusive) {
#if HAVE_FLOCK
auto Start = std::chrono::steady_clock::now();
auto End = Start + Timeout;
do {
if (flock(FD, (Exclusive ? LOCK_EX : LOCK_SH) | LOCK_NB) == 0)
return std::error_code();
int Error = errno;
if (Error == EWOULDBLOCK) {
// Match sys::fs::tryLockFile, which sleeps for 1 ms per attempt.
std::this_thread::sleep_for(std::chrono::milliseconds(1));
continue;
}
return std::error_code(Error, std::generic_category());
} while (std::chrono::steady_clock::now() < End);
return make_error_code(std::errc::no_lock_available);
#elif defined(_WIN32)
// On Windows this implementation is thread-safe.
return sys::fs::tryLockFile(FD, Timeout, Exclusive);
#else
return make_error_code(std::errc::no_lock_available);
#endif
}
Expected<size_t> cas::ondisk::preallocateFileTail(int FD, size_t CurrentSize, size_t NewSize) {
auto CreateError = [&](std::error_code EC) -> Expected<size_t> {
if (EC == std::errc::not_supported)
// Ignore ENOTSUP in case the filesystem cannot preallocate.
return NewSize;
#if defined(HAVE_POSIX_FALLOCATE)
if (EC == std::errc::invalid_argument &&
CurrentSize < NewSize && // len > 0
NewSize < std::numeric_limits<off_t>::max()) // 0 <= offset, len < max
// Prior to 2024, POSIX required EINVAL for cases that should be ENOTSUP,
// so handle it the same as above if it is not one of the other ways to
// get EINVAL.
return NewSize;
#endif
return createStringError(EC, "failed to allocate to CAS file: " + EC.message());
};
#if defined(HAVE_POSIX_FALLOCATE)
// Note: posix_fallocate returns its error directly, not via errno.
if (int Err = posix_fallocate(FD, CurrentSize, NewSize - CurrentSize))
return CreateError(std::error_code(Err, std::generic_category()));
return NewSize;
#elif defined(__APPLE__)
fstore_t FAlloc;
FAlloc.fst_flags = F_ALLOCATEALL | F_ALLOCATEPERSIST;
FAlloc.fst_posmode = F_PEOFPOSMODE;
FAlloc.fst_offset = 0;
FAlloc.fst_length = NewSize - CurrentSize;
FAlloc.fst_bytesalloc = 0;
if (fcntl(FD, F_PREALLOCATE, &FAlloc))
return CreateError(errnoAsErrorCode());
assert(CurrentSize + FAlloc.fst_bytesalloc >= NewSize);
return CurrentSize + FAlloc.fst_bytesalloc;
#else
return NewSize; // Pretend it worked.
#endif
}
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