Re: [pve-devel] [PATCH storage v2] fix #957 iscsi: improve check_connection logic

[Mira Limbeck <m.limbeck@proxmox.com>]

Thank you for the v2!

some comments inline
> +sub iscsi_test_session {
> +    my ($sid) = @_;
> +    my $cmd = [$ISCSIADM, '--mode', 'session', '--sid', $sid, '-P1'];
> +
> +    my $res = 0;
> +    eval {
> +        run_command($cmd, errmsg => 'iscsi session test failed', outfunc => sub {
> +            my $line = shift;
> +            if ($line =~ m/^\s+iSCSI Session State: LOGGED_IN\s*$/) {
> +                $res = 1;
> +            }
> +        });
> +    };
> +    if (my $err = $@) {
> +        die $err;
> +    };
This can be written as just `die "$@\n" if $@` instead.
It should contain some additional info though, for example:
`die "session check failed: $@\n" if $@;`

> +    return $res;
> +}
> +
>  sub iscsi_portals {
>      my ($target, $portal_in) = @_;
>  
> @@ -560,11 +579,24 @@ sub activate_volume {
>  sub check_connection {
>      my ($class, $storeid, $scfg) = @_;
>  
> -    my $portals = iscsi_portals($scfg->{target}, $scfg->{portal});
> -
> -    for my $portal (@$portals) {
> -	my $result = iscsi_test_portal($portal);
> -	return $result if $result;
> +    my $cache = {};
> +    my $sessions = [];
> +    eval {
> +        $sessions = iscsi_session($cache, $scfg->{target});
> +    };
iscsi_session only dies if the `iscsiadm` command fails or prints
something other than `: No active sessions.`. See the `!~` check in
iscsi_session_list.

> +    if (my $err = $@) {
This will not be the case when there are no sessions, but when the
iscsiadm command fails. See above.

> +        # no sessions, check portal via tcp
> +        my $portals = iscsi_portals($scfg->{target}, $scfg->{portal});
> +        for my $portal (@$portals) {
> +            my $result = iscsi_test_portal($portal);
> +            return $result if $result;
> +        }
> +        return 0;
> +    }
> +    # we have sessions, let's test them instead
> +    for my $session (@$sessions) {
> +        my $result = iscsi_test_session($session->{session_id});
> +        return $result if $result;
>      }
>  
>      return 0;
You could do something like this:
```
    my $cache = {};
    my $sessions = iscsi_session($cache, $scfg->{target});
    my $portals = iscsi_portals($scfg->{target}, $scfg->{portal});
    for my $portal ($portals->@*) {
	my $session_exists = 0;
    	for my $session ($sessions->@*) {
	    next if $session->{portal} ne $portal;
	    $session_exists = 1;

	    my $result = iscsi_test_session($session->{session_id});
	    return $result if $result;
	}
	next if $session_exists;

	my $result = iscsi_test_portal($portal);
	return $result if $result;
    }
```
This goes through all portals, and if a session exists for the portal,
does a session test instead of the tcp_ping.
But if no session exists, it still checks with a tcp_ping to see if we
should login or not.


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