zero_extent.cpp

#include "zero_extent.h"

#include <util/string/builder.h>
#include <util/system/file.h>

#include <limits>

#if defined(__linux__)
// This exists because on sandbox builds we have newer kernels with much older UAPI headers
// If kernel does not actually support this we will get a proper error in runtime
#   if !defined(FALLOC_FL_ZERO_RANGE)
#       define FALLOC_FL_ZERO_RANGE 0x10
#   endif
#   include <errno.h>
#   include <fcntl.h>
#   include <malloc.h>
#   include <sys/types.h>
#endif

namespace NCloud::NBlockStore::NServer {

////////////////////////////////////////////////////////////////////////////////

NProto::TError ZeroFileExtent(
    TFileHandle& fileHandle,
    i64 offset,
    i64 length) noexcept
{
#if defined(__linux__)
    if (length > std::numeric_limits<off_t>::max() ||
        offset > std::numeric_limits<off_t>::max())
    {
        return MakeError(E_ARGUMENT);
    }

    // On linux we have FALLOC_FL_ZERO_RANGE (or even PUNCH_HOLE, but let's not get carried away)
    int res = fallocate(FHANDLE(fileHandle), FALLOC_FL_ZERO_RANGE, offset, length);
    if (res == 0) {
        return {};
    }

    if (errno != EOPNOTSUPP) {
        return MakeError(E_IO, TStringBuilder()
            << "FALLOC_FL_ZERO_RANGE failed: " << errno << " "
            << strerror(errno));
    }

#endif

    // Not supported

    NProto::TError error;
    error.SetCode(E_NOT_IMPLEMENTED);

    return error;
}

}   // namespace NCloud::NBlockStore::NServer