From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: blk_iopoll_enabled Date: Wed, 12 Mar 2014 21:40:27 -0600 Message-ID: <532128AB.6010803@kernel.dk> References: <53209ACB.2080708@dev.mellanox.co.il> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pb0-f45.google.com ([209.85.160.45]:40178 "EHLO mail-pb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752729AbaCMDkb (ORCPT ); Wed, 12 Mar 2014 23:40:31 -0400 Received: by mail-pb0-f45.google.com with SMTP id uo5so475859pbc.18 for ; Wed, 12 Mar 2014 20:40:30 -0700 (PDT) In-Reply-To: <53209ACB.2080708@dev.mellanox.co.il> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Sagi Grimberg Cc: Bart Van Assche , Or Gerlitz , Oren Duer , linux-scsi 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. -- Jens Axboe