From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 3E52A6B006A for ; Thu, 14 Jan 2010 07:45:41 -0500 (EST) Date: Thu, 14 Jan 2010 23:45:26 +1100 From: Nick Piggin Subject: Re: [PATCH 5/8] vmalloc: simplify vread()/vwrite() Message-ID: <20100114124526.GB7518@laptop> References: <20100113135305.013124116@intel.com> <20100113135957.833222772@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100113135957.833222772@intel.com> Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Andrew Morton , LKML , Tejun Heo , Ingo Molnar , Andi Kleen , Hugh Dickins , Christoph Lameter , KAMEZAWA Hiroyuki , Linux Memory Management List List-ID: On Wed, Jan 13, 2010 at 09:53:10PM +0800, Wu Fengguang wrote: > vread()/vwrite() is only called from kcore/kmem to access one page at a time. > So the logic can be vastly simplified. > > The changes are: > - remove the vmlist walk and rely solely on vmalloc_to_page() > - replace the VM_IOREMAP check with (page && page_is_ram(pfn)) > - rename to vread_page()/vwrite_page() > > The page_is_ram() check is necessary because kmap_atomic() is not > designed to work with non-RAM pages. I don't know if you can really do this. Previously vmlist_lock would be taken, which will prevent these vm areas from being freed. > Note that even for a RAM page, we don't own the page, and cannot assume > it's a _PAGE_CACHE_WB page. So why is this not a problem for your patch? I don't see how you handle it. What's the problem with the current code, exactly? I would prefer that you continue using the same vmlist locking and checking for validating addresses. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org