[systemd-devel] nspawn blocks sync_file_range on arm

[Steve Dodd]

ARM has two sync_file_range syscalls, sync_file_range and sync_file_range2.
The former is apparently not used, and glibc calls the latter whenever a
userspace program calls sync_file_range. I'm guessing systemd-nspawn
doesn't know this, because the follow code consistently fails in an nspawn
container on ARM:

#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

void main()
{
        int f = open("/tmp/syncrange.test",O_CREAT|O_RDWR,0666);
        int r=sync_file_range(f, 0, 0, 0);
        if (r)
                perror("sync_file_range");
        close(f);
}

This seems to be causing problems specifically for borg(backup) and
postgres:
https://github.com/borgbackup/borg/issues/4710
https://www.postgresql.org/message-id/flat/CA%2BhUKG%2BydOUT4zjxb6QmJWy8U9WbC-q%2BJWV7wLsEY9Df%3Dmw0Mw%40mail.gmail.com#ac8f14897647dc7eae3c7e7cbed36d93

I will test the obvious fix when I can, unless someone beats me to it :)

S.
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