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🍒[6.2][llvm][cas] Fix error handling of posix_fallocate #11054

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Merged
merged 1 commit into from
Jul 24, 2025
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🍒[6.2][llvm][cas] Fix error handling of posix_fallocate #11054

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20 changes: 15 additions & 5 deletions llvm/lib/CAS/OnDiskCommon.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include "llvm/Config/config.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Process.h"
#include <limits>
#include <mutex>
#include <optional>
#include <thread>
Expand Down Expand Up @@ -115,16 +116,25 @@ cas::ondisk::tryLockFileThreadSafe(int FD, std::chrono::milliseconds Timeout,
}

Expected<size_t> cas::ondisk::preallocateFileTail(int FD, size_t CurrentSize, size_t NewSize) {
auto CreateErrorFromErrno = [&]() -> Expected<size_t> {
std::error_code EC = errnoAsErrorCode();
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)
if (posix_fallocate(FD, CurrentSize, NewSize - CurrentSize))
return CreateErrorFromErrno();
// 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;
Expand All @@ -134,7 +144,7 @@ Expected<size_t> cas::ondisk::preallocateFileTail(int FD, size_t CurrentSize, si
FAlloc.fst_length = NewSize - CurrentSize;
FAlloc.fst_bytesalloc = 0;
if (fcntl(FD, F_PREALLOCATE, &FAlloc))
return CreateErrorFromErrno();
return CreateError(errnoAsErrorCode());
assert(CurrentSize + FAlloc.fst_bytesalloc >= NewSize);
return CurrentSize + FAlloc.fst_bytesalloc;
#else
Expand Down