Hi,

according to the Linux man page of fsync(2):

Calling fsync() does not necessarily ensure that the entry in the directory containing the file has also reached disk. For that an explicit fsync() on a file descriptor for the directory is also needed.

So, how do we fsync directories in Perl? perldoc POSIX says that fsync() should be done with the sync method in IO::Handle. So I tried this with a directory:

use IO::Handle;
open my $f, '/tmp' or die $!;
$f->sync or die "fsync: $!\n";
[download]

This bails out with "fsync: Invalid argument". According to strace, no fsync syscall is even tried.

I tried opendir too:

use IO::Handle;
my $f = IO::Handle->new;
opendir $f, '/tmp' or die $!;
$f->sync or die "fsync: $!\n";
[download]

with the same result.

On the other hand, an equivalent C program succeeds and properly calls fsync according to strace:

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

int main (void) {
    int fd = open("/tmp", 0);
    if (fd < 0) {
        perror("open: /tmp");
        exit(1);
    }
    if (fsync(fd) < 0) {
        perror("fsync: /tmp");
        exit(1);
    }
    return 0;
}
[download]

My question: What is the proper way to do fsync with directories in Perl? Or is this just a bug in IO::Handle?

(All tests have been done on a current Debian Squeeze (testing) with perl 5.10.1-12.)

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