Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756449AbZCLP6l (ORCPT ); Thu, 12 Mar 2009 11:58:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752954AbZCLP6b (ORCPT ); Thu, 12 Mar 2009 11:58:31 -0400 Received: from mtagate2.de.ibm.com ([195.212.17.162]:50327 "EHLO mtagate2.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753155AbZCLP6a (ORCPT ); Thu, 12 Mar 2009 11:58:30 -0400 Date: Thu, 12 Mar 2009 16:54:51 +0100 From: Martin Schwidefsky To: Matt Mackall Cc: Alexey Dobriyan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gerald Schaefer , akpm@linux-foundation.org Subject: Re: [PATCH] acquire mmap semaphore in pagemap_read. Message-ID: <20090312165451.1a7ef22f@skybase> In-Reply-To: <1236871414.3213.50.camel@calx> References: <20090312113308.6fe18a93@skybase> <20090312114533.GA2407@x200.localdomain> <20090312125410.25400d18@skybase> <1236871414.3213.50.camel@calx> Organization: IBM Corporation X-Mailer: Claws Mail 3.7.1 (GTK+ 2.14.7; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1281 Lines: 30 On Thu, 12 Mar 2009 10:23:34 -0500 Matt Mackall wrote: > Well it means we may have to reintroduce the very annoying double > buffering from various earlier implementations. But let's leave this > discussion until after we've figured out what to do about the walker > code. About the walker code. I've realized that there is another way to fix this. The TASK_SIZE definition is currently used for two things: 1) as a maximum mappable address, 2) the size of the address space for a process. And there lies a problem: while a process is using a reduced page table 1) and 2) differ. If I make TASK_SIZE give you the current size of the address space then it is not possible to mmap an object beyond 4TB and the page table upgrade never happens. If I make TASK_SIZE return the maximum mappable address the page table walker breaks. The solution could be to introduce MAX_TASK_SIZE and use that in the mmap code to find out what can be mapped. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/