From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chris Friesen" Subject: questions on details of sg_ioctl Date: Tue, 13 Nov 2007 10:00:16 -0600 Message-ID: <4739CA10.6080601@nortel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from zcars04f.nortel.com ([47.129.242.57]:37415 "EHLO zcars04f.nortel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751400AbXKMQAa (ORCPT ); Tue, 13 Nov 2007 11:00:30 -0500 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Suppose I send down an SG_IO command on a generic scsi device node. As far as I can tell, the code path looks like this in 2.6.14: sg_ioctl sg_new_write scsi_execute_async (sets up sg_cmd_done as callback) scsi_do_req scsi_insert_special_req blk_insert_request and like this in 2.6.23: sg_ioctl sg_new_write scsi_execute_async (sets up sg_cmd_done as callback) blk_execute_rq_nowait At this point, is that request queued along with all the other commands, or is it injected immediately to the device? If it is queued up along with all the other commands, shouldn't the return path feed into the queue length calculations if we get BUSY/TASK_SET_FULL? Also, for the purposes of the device returning TASK_SET_FULL vs BUSY, does each userspace process count as a SCSI initiator port, or are they all sort of grouped together? (The reason I ask is that we're getting TASK_SET_FULL errors but according to SAM-3 that should only happen if we already have at least one outstanding request.) Thanks, Chris