[stgt] [PATCH] ISCSI: Honour MaxRecvDataSegmentLength for NORMAL sessions

[FUJITA Tomonori]

On Sat, 18 Aug 2012 09:03:54 +1000
Ronnie Sahlberg <ronniesahlberg at gmail.com> wrote:

> Fix a bug in iscsid.c with regards to MaxRecvDataSegmentLength.
> The parsing of this login key only updated the settings for how large PDUs we can send for DISCOVERY sessions.

Really? I thought that we call param_set_val() for
ISCSI_PARAM_MAX_XMIT_DLENGTH in SESSION_NORMAL. If you configure
ISCSI_PARAM_MAX_XMIT_DLENGTH, tgtd honors MaxRecvDataSegmentLength
that an initiator sends?

tgtadm --op show --mode target --tid 1 MaxRecvDataSegmentLength=8192


btw, can you send a single patch? You don't need to split one patch
into two parts: a patch description and an actual patch.


> What we want here is to have the MaxRecvDataSegmentLength to be parsed and applied to NORMAL sessions, not DISCOVERY sessions.
> 
> Otherwise, we will always have this clamped down to 8k for all normal sessions  and thus we get a performance issue since TGTD will always send DATA-IN PDUs of just 8kb each.
> 
> With this patch, TGTD now honours the setting so that if the initiator specifies MaxDataSegmentLength to something reasonable like 256k, then TGTD will be able to send a single PDU of 256kb instead of a train of 32 8kb PDUs.
> 
> Signed-off-by: Ronnie Sahlberg <ronniesahlberg at gmail.com>
> ---
>  usr/iscsi/iscsid.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/usr/iscsi/iscsid.c b/usr/iscsi/iscsid.c
> index 96abbfc..84476f7 100644
> --- a/usr/iscsi/iscsid.c
> +++ b/usr/iscsi/iscsid.c
> @@ -346,7 +346,7 @@ static void text_scan_login(struct iscsi_connection *conn)
>  				continue;
>  			}
>  			if (idx == ISCSI_PARAM_MAX_XMIT_DLENGTH &&
> -			    conn->session_type == SESSION_DISCOVERY)
> +			    conn->session_type == SESSION_NORMAL)
>  				conn->session_param[idx].val = val;
>  			else
>  				param_set_val(session_keys,
> -- 
> 1.7.3.1
> 
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