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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham 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 D310DC4321E for ; Thu, 6 Sep 2018 22:42:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DE2020659 for ; Thu, 6 Sep 2018 22:42:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=thunk.org header.i=@thunk.org header.b="uPSPXBMt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DE2020659 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728268AbeIGDUG (ORCPT ); Thu, 6 Sep 2018 23:20:06 -0400 Received: from imap.thunk.org ([74.207.234.97]:60732 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726116AbeIGDUF (ORCPT ); Thu, 6 Sep 2018 23:20:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=slsTku73Cxw/ihQxR6Z0iOhKkYfMux615hAUa0qRy7U=; b=uPSPXBMtkyaLBYDSRCqYIoLG0y U1MfNTK/A7Zbog4x2EYn7VQGB7512NmJsfykl4Euv51SloLdMbqbI4psG60ORH5WnTR5zcSft1qQS 6ngyqQUuR2OZKntpk55zBzqUcootRkVPgq8jRmyOl0l4w4FP7RslBEUzqZFXZ+DLcmq0=; Received: from root (helo=callcc.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.89) (envelope-from ) id 1fy2yZ-0007vp-Dx; Thu, 06 Sep 2018 22:42:11 +0000 Received: by callcc.thunk.org (Postfix, from userid 15806) id A19477A5675; Thu, 6 Sep 2018 18:42:10 -0400 (EDT) Date: Thu, 6 Sep 2018 18:42:10 -0400 From: "Theodore Y. Ts'o" To: Bart Van Assche Cc: Xuewei Zhang , "James E . J . Bottomley" , "Martin K . Petersen" , Ming Lei , Hannes Reinecke , Christoph Hellwig , Paolo Bonzini , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Aditya Kali , Guenter Roeck , maze@google.com Subject: Re: [PATCH] scsi: sd: Contribute to randomness when running rotational device Message-ID: <20180906224210.GK5098@thunk.org> Mail-Followup-To: "Theodore Y. Ts'o" , Bart Van Assche , Xuewei Zhang , "James E . J . Bottomley" , "Martin K . Petersen" , Ming Lei , Hannes Reinecke , Christoph Hellwig , Paolo Bonzini , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Aditya Kali , Guenter Roeck , maze@google.com References: <20180906203719.209399-1-xueweiz@google.com> <1536272873.26747.11.camel@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1536272873.26747.11.camel@acm.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 03:27:53PM -0700, Bart Van Assche wrote: > > Although this patch looks fine to me, seeing this patch makes me wonder > whether the default should be changed (QUEUE_FLAG_MQ_DEFAULT) instead of > modifying the sd driver. Can anyone remind me why QUEUE_FLAG_MQ_DEFAULT does > not include QUEUE_FLAG_ADD_RANDOM? There was a discussion about a number of *years* ago; blk-mq has been baking for a very long time. In the early days of block_mq, the overwhelming percentage of the users of blk-mq where those who were using PCIe attached flash. So when, I raised this question, the argument was that SSD users have no entropy. Which I agree with; but now that blk-mq is the default, and hard drives are using blk-mq, it's time for a patch like Xuewei's. Cheers, - Ted