fs.copyFile fails copying from nfs source to nfs dest file.

[moqtadir]

When copying a file from nfs mount to the same nfs mount, fs.copyFileSync fails with ENOTSUP error.
This was not replicated in Node 12.x, but is reproducible consistently in node v14.15.1

To reproduce using 2 line test file
Using node 14.15.1 on CentOS 7 X86_64
And make sure /mnt/nfs_assets/ is an nfs4 mount.

[root@local]# cat <<'EOF' > test.js
const fs = require('fs');
fs.copyFileSync('/mnt/nfs_assets/source.txt', '/mnt/nfs_assets/dest.txt');
EOF

[root@local]# cat <<'EOF' > /mnt/nfs_assets/source.txt
foorbar
EOF

[root@local]# node test.js
internal/fs/utils.js:308
    throw err;
    ^

Error: ENOTSUP: operation not supported on socket, copyfile '/mnt/nfs_assets/source.txt' -> '/mnt/nfs_assets/dest.txt'
    at Object.copyFileSync (fs.js:1991:3)
    at Object.<anonymous> (/home/user/test.js:2:4)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Module.load (internal/modules/cjs/loader.js:928:32)
    at Function.Module._load (internal/modules/cjs/loader.js:769:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:72:12)
    at internal/main/run_main_module.js:17:47 {
  errno: -95,
  syscall: 'copyfile',
  code: 'ENOTSUP',
  path: '/mnt/nfs_assets/source.txt',
  dest: '/mnt/nfs_assets/dest.txt'
}

I haven't researched this much, but the ifdef (linux) second was added recently and is now using the copyfile call but does not account for ENOTSUP being returned?

node/deps/uv/src/unix/fs.c

Line 904 in feab91a

#ifdef __linux__

Relevant commit.
cf34854

Please let me know if you need any additional information.

[Trott]

@nodejs/libuv Reporter suspects the cited libuv change.

[Trott]

@moqtadir The commit you refer to is in Node.js 14.9.0 but not 14.8.0. Are you able to test with those two versions to confirm that 14.8.0 does not exhibit the bug and 14.9.0 does?

[moqtadir]

@Trott Apologize for the delay, not sure why I didn't get notified on your comments.

Yes I can confirm issue doesn't happen on 14.8 but does on 14.9 - see below for all commands I ran to verify this.

[root@local ~]# # /mnt/nfs_mount is an nfs4 mounted path, create source file to copy.
[root@local ~]# echo "test-data" > /mnt/nfs_mount/source.txt
[root@local ~]# # using docker to test node 14.8 and 14.9 with the same one line script to copy file.
[root@local ~]# docker run   -v /mnt/nfs_mount:/mnt/nfs_mount node:14.8.0-slim node -e "require('fs').copyFileSync('/mnt/nfs_mount/source.txt', '/mnt/nfs_mount/dest.txt');"
[root@local ~]# #check file copied - yes
[root@local ~]# ls /mnt/nfs_mount/dest.txt
/mnt/nfs_mount/dest.txt
[root@local ~]# /bin/rm -f /mnt/nfs_mount/dest.txt  #cleanup dest file before testing 14.9
[root@local ~]# docker run   -v /mnt/nfs_mount:/mnt/nfs_mount node:14.9.0-slim node -e "require('fs').copyFileSync('/mnt/nfs_mount/source.txt', '/mnt/nfs_mount/dest.txt');"
internal/fs/utils.js:298
    throw err;
    ^

Error: ENOTSUP: operation not supported on socket, copyfile '/mnt/nfs_mount/source.txt' -> '/mnt/nfs_mount/dest.txt'
    at Object.copyFileSync (fs.js:1941:3)
    at [eval]:1:15
    at Script.runInThisContext (vm.js:132:18)
    at Object.runInThisContext (vm.js:309:38)
    at Object.<anonymous> ([eval]-wrapper:10:26)
    at Module._compile (internal/modules/cjs/loader.js:1075:30)
    at evalScript (internal/process/execution.js:92:25)
    at internal/main/eval_string.js:23:3 {
  errno: -95,
  syscall: 'copyfile',
  code: 'ENOTSUP',
  path: '/mnt/nfs_mount/source.txt',
  dest: '/mnt/nfs_mount/dest.txt'
}

[mmomtchev]

copy_file_range appeared in Linux kernel 4.5 but some newer glibc versions will provide a user-space shim if the kernel support is not present.
@moqtadir , CentOS 7 does not support either of them.
This is a very useful syscall, especially on NFS/CIFS where the copy is supposed to be handled entirely server-side, so I think it should stay.
But maybe a correct auto-detection is to be implemented? @Trott @cjihrig ?

[mmomtchev]

@moqtadir , can you please try to compile and run this on your platform:

#define _GNU_SOURCE  
#include <unistd.h>
#include <sys/syscall.h>
#include <stdio.h>
#include <errno.h>

#ifndef __NR_copy_file_range
#define __NR_copy_file_range (-1)
#endif

int main() {
    int r = syscall(326, 4, 0, 5, 0, 1024, 0);
    printf("r is %d, errno is %d, copy_file_range %d\n", r, errno, __NR_copy_file_range);
}

[mmomtchev]

Or maybe directly this replacing existing_nfs_file and new_nfs_file

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>

#ifndef __NR_copy_file_range
#define __NR_copy_file_range (-1)
#endif

int main() {
    int in = open("existing_nfs_file", O_RDONLY);
    int out = open("new_nfs_file", O_CREAT | O_TRUNC | O_WRONLY, S_IRUSR | S_IWUSR);
    int r = syscall(326, in, 0, out, 0, 1, 0);
    printf("in is %d, out is %d, r is %d, errno is %d, copy_file_range %d\n",
            in, out, r, errno, __NR_copy_file_range);
}

[moqtadir]

@mmomtchev The result is below

root@3e2cc13f258f:/# ./a.out
in is 3, out is 4, r is -1, errno is 95, copy_file_range 326

[moqtadir]

Also by the way, there was a similar issue in golang and they basically added exception for ENOTSUPP in addition to EINVAL because a copyfilerange on an NFS mount can return ENOTSUP.

golang/go#40731

[mmomtchev]

@moqtadir , yes precisely, this is the problem and the right solution

[piccit]

Is there a workaround for this? I'm unclear on the timeline on how long it will take for that libuv fix to be released

[Trott]

Is there a workaround for this? I'm unclear on the timeline on how long it will take for that libuv fix to be released

I don't have a workaround to suggest but a fix has landed in the libuv code base but has not yet made it into a release. Should be in the next libuv release I imagine, though.

[moqtadir]

Is there a workaround for this? I'm unclear on the timeline on how long it will take for that libuv fix to be released

You can use require('child_process').spawnSync('/bin/cp', ['-bf', fromFile, toFile], { stdio: 'ignore' })
Obviously adjust flags and copy command to your need based on platform.
Alternatively open the source and destination file streams and copy chunks yourself.