From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761881AbYENIJC (ORCPT ); Wed, 14 May 2008 04:09:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932158AbYENIIT (ORCPT ); Wed, 14 May 2008 04:08:19 -0400 Received: from relay.2ka.mipt.ru ([194.85.82.65]:42732 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932119AbYENIIN (ORCPT ); Wed, 14 May 2008 04:08:13 -0400 Date: Wed, 14 May 2008 12:08:01 +0400 From: Evgeniy Polyakov To: Andrew Morton Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: POHMELFS high performance network filesystem. Transactions, failover, performance. Message-ID: <20080514080801.GE28330@2ka.mipt.ru> References: <20080513174523.GA1677@2ka.mipt.ru> <20080513233341.47edea7f.akpm@linux-foundation.org> <20080514074028.GA28330@2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080514074028.GA28330@2ka.mipt.ru> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 14, 2008 at 11:40:28AM +0400, Evgeniy Polyakov (johnpol@2ka.mipt.ru) wrote: > > If any thread takes more than one kmap() at a time, it is deadlockable. > > Because there is a finite pool of kmaps. Everyone can end up holding > > one or more kmaps, then waiting for someone else to release one. > > It never takes the whole LAST_PKMAP maps. So the same can be applied to > any user who kmaps at least one page - while user waits for free slot, > it can be reused by someone else and so on. Actually CIFS uses the same logic: maps multiple pages in wrteback path and release them after received reply. -- Evgeniy Polyakov