Nonsense UNKNOWN error when writing large buffers with fs.writev
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- JavaScript
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Description
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
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at fs.writevSync in fs.js and compare its argument handling with the fs.write validation referenced by commit c4e7dca8f30ff89b42e96fb8819558ed518a72dd. Reproduce the large-buffer case on Linux, then determine whether the finished behavior should reject the request with a proper error before the syscall or support the larger buffer through libuv.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, node.js
- Domain
- backend, operating-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100