From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11577CA9EC4 for ; Tue, 29 Oct 2019 15:15:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E60F8208E3 for ; Tue, 29 Oct 2019 15:15:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389947AbfJ2PPA (ORCPT ); Tue, 29 Oct 2019 11:15:00 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:37528 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389841AbfJ2PPA (ORCPT ); Tue, 29 Oct 2019 11:15:00 -0400 Received: by mail-pg1-f195.google.com with SMTP id p1so9812056pgi.4; Tue, 29 Oct 2019 08:14:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=BpdmLBrAF6vIWkMIKjmn2Nztml/ALZp4Q1mNNsAX6zA=; b=FBsBZ4/PgKstuD1cHzrx6zoEP5CihEbcCLMklC6ghK9nhCqT3mvifXe6kDyT4U4dAa /QHluUsOMOCxQJqj/hgPPHvOPSLQE3VAraEJ97ArqqO+fRitOt1ahmLoTJ4ucEoLJujm HJSJzRGIXOQ4EQVevIiH8r75DGjdjT+jkEWa+wGui3Ht0ynnrooj2DSpvndmv96fUPOH T+UEL5GclguyhzK4faFjhnP5YzJIEcogvNn6T55G3LIa3PflLJwMy1vTRMpUrvBZX0SY 5f82WL+VD4sqd2DIKNO26aY1eIEoy6724VeuCE2V4p6MXn5ehInwSY3FLpKa+dQlbsHw 8COw== X-Gm-Message-State: APjAAAUHKSCduG9EfkVTlsKC0T7vxRB/wWcYJePkueZiE/WAeE4i2iYz g9jgNCK1h6Fk9G29fMhAzHc= X-Google-Smtp-Source: APXvYqyQhKFHzk7jdh70TLLVp4Cwd9bRfe/8VfkXsoeqpWNgAlOI0jsF0Xy+1MCAqUR+aa0JrHEGHg== X-Received: by 2002:a63:cf45:: with SMTP id b5mr27606615pgj.36.1572362098980; Tue, 29 Oct 2019 08:14:58 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id s23sm13708158pgh.21.2019.10.29.08.14.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Oct 2019 08:14:58 -0700 (PDT) Subject: Re: [PATCH] scsi: Fix scsi_get/set_resid() interface To: Damien Le Moal , "linux-scsi@vger.kernel.org" , "Martin K . Petersen" , "linux-usb@vger.kernel.org" , "usb-storage@lists.one-eyed-alien.net" , Alan Stern , Greg Kroah-Hartman Cc: Justin Piszcz References: <20191028105732.29913-1-damien.lemoal@wdc.com> From: Bart Van Assche Message-ID: <7b3cad63-3c0d-0bff-b400-acf85344bfee@acm.org> Date: Tue, 29 Oct 2019 08:14:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 10/29/19 1:17 AM, Damien Le Moal wrote: > So I think changing the interface to unsigned int makes sense in that > context. Also, unless I am reading this wrong, the above definition you > quote always lead to resid >= 0, so I do not see what problem you are > worried about. Could you elaborate your concerns please ? Hi Damien, SCSI LLDs handle residual overflow in at least two different ways. I think the iSCSI initiator handles this by reporting the DID_BAD_TARGET error code. In the tcm_loop driver I found the following, which I think is incorrect: set_host_byte(sc, DID_OK); if ((se_cmd->se_cmd_flags & SCF_OVERFLOW_BIT) || (se_cmd->se_cmd_flags & SCF_UNDERFLOW_BIT)) scsi_set_resid(sc, se_cmd->residual_count); Seeing this made me wonder what the best approach is for a SCSI LLD to report a residual overflow? Thanks, Bart.