From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: blk_iopoll_enabled Date: Thu, 13 Mar 2014 20:48:50 +0200 Message-ID: <5321FD92.6020700@dev.mellanox.co.il> References: <53209ACB.2080708@dev.mellanox.co.il> <532128AB.6010803@kernel.dk> <5321CFF0.8020209@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ee0-f51.google.com ([74.125.83.51]:53755 "EHLO mail-ee0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755164AbaCMSsy (ORCPT ); Thu, 13 Mar 2014 14:48:54 -0400 Received: by mail-ee0-f51.google.com with SMTP id c13so595428eek.24 for ; Thu, 13 Mar 2014 11:48:52 -0700 (PDT) In-Reply-To: <5321CFF0.8020209@kernel.dk> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: Bart Van Assche , Or Gerlitz , Oren Duer , linux-scsi On 3/13/2014 5:34 PM, Jens Axboe wrote: > On 03/12/2014 09:40 PM, Jens Axboe wrote: >> On 2014-03-12 11:35, Sagi Grimberg wrote: >>> Hey Jens, >>> >>> So I'm looking at blk_iopoll for iSER & SRP and I have one gap I would >>> like to get your input on. >>> >>> In blk-iopoll.c I see: >>> int blk_iopoll_enabled = 1; >>> EXPORT_SYMBOL(blk_iopoll_enabled); >>> >>> This is set to 1 and exported for everyone to condition and *modify* >>> it. >>> The documentation says the user must check this when using blk_iopoll. >>> >>> My question is why? it should always be true shouldn't it? >>> Moreover, isn't it better to protect it using a get() function of it? >>> can't someone set it to 0 and shutdown the lights on everyone else? >> >> We can kill it. IIRC, it was mostly used during development to test >> functionality and performance (and wired to a sysfs toggle file). >> >> But... Just because it's exported doesn't mean that random users are >> allowed to just disable it. What's left now is an always-on, so we can >> remove it. > > It _is_ still exported, I just forgot it was put in sysctl. I'll kill > it off completely now. It's safe to toggle from user space, but only > practically so if IO is idle. It makes no attempt to ensure that, as > it was just a debug thing. > Thanks Sagi.