Nonsense UNKNOWN error when writing large buffers with fs.writev

Version

14.18.1

Platform

Linux ops 5.11.0-1021-gcp #23~20.04.1-Ubuntu SMP Fri Oct 1 19:04:32 UTC 2021 x86_64 x86_64 x86_64 GNU/Linu

Subsystem

fs

What steps will reproduce the bug?

const fs = require("fs");
const fd = fs.openSync("./test.dat", fs.constants.O_WRONLY | fs.constants.O_CREAT, 0o666);
const bufs = [Buffer.alloc(0x7FFFFFFF + 1)];
fs.writevSync(fd, bufs, 0);

This throws

Uncaught Error: UNKNOWN: unknown error, write
    at Object.writevSync (fs.js:749:3) {
  errno: -2147483648,
  syscall: 'write',
  code: 'UNKNOWN'
}

That errno is 0x7fffffff + 1 wrapped around.

How often does it reproduce? Is there a required condition?

Always.

What is the expected behavior?

Should either work, since pwritev(2) works (I don't know if it has a limit less than SSIZE_MAX), or report a proper error before making the syscall. I did the latter recently for fs.write in c4e7dca8f30ff89b42e96fb8819558ed518a72dd. It would be nice if large files actually worked, but the best fix for that would require a new libuv function.

What do you see instead?

No response

Additional information

No response

fs.js の fs.writevSync から始め、引数の処理を、コミット c4e7dca8f30ff89b42e96fb8819558ed518a72dd で参照されている fs.write の検証と比較します。Linux で大きなバッファーのケースを再現し、その後、完成した動作では syscall の前に適切なエラーでリクエストを拒否すべきか、それとも libuv を通じてより大きなバッファーをサポートすべきかを判断します。