From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932344AbcECFzm (ORCPT ); Tue, 3 May 2016 01:55:42 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:35558 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751066AbcECFzl (ORCPT ); Tue, 3 May 2016 01:55:41 -0400 Date: Tue, 3 May 2016 14:57:15 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Sergey Senozhatsky , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] zram: user per-cpu compression streams Message-ID: <20160503055715.GC25545@swordfish> References: <1461860230-849-1-git-send-email-sergey.senozhatsky@gmail.com> <1461860230-849-3-git-send-email-sergey.senozhatsky@gmail.com> <20160502062311.GB6077@bbox> <20160502072508.GA1811@swordfish> <20160502080600.GB1811@swordfish> <20160503052324.GB17316@bbox> <20160503054011.GA5972@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160503054011.GA5972@blaptop> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (05/03/16 14:40), Minchan Kim wrote: [..] > > At least, we need sanity check code, still? > > Otherwise, user can echo "garbage" > /sys/xxx/max_comp_stream" and then > > cat /sys/xxx/max_comp_stream returns num_online_cpus. > > One more thing, > > User: > echo 4 > /sys/xxx/max_comp_stream" > cat /sys/xxx/max_comp_streams > 8 sure, it can also be cat /sys/xxx/max_comp_streams 5 cat /sys/xxx/max_comp_streams 6 cat /sys/xxx/max_comp_streams 7 cat /sys/xxx/max_comp_streams 3 depending on the availability of CPUs. but why would user space constantly check max_comp_streams? > which is rather weird? > > We should keep user's value and return it to user although it's techically > lying. IMO, it would be best way to prevent confusing for user until we > removes max_comp_streams finally. well, I preferred to show the actual state of the device. besides, does anyone really do write buffer to file if (success) read from file and compare with the buffer ? -ss