Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751836AbaBRS2O (ORCPT ); Tue, 18 Feb 2014 13:28:14 -0500 Received: from mail-vc0-f172.google.com ([209.85.220.172]:51180 "EHLO mail-vc0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751178AbaBRS2M (ORCPT ); Tue, 18 Feb 2014 13:28:12 -0500 MIME-Version: 1.0 In-Reply-To: <20140218180730.C2552E0090@blue.fi.intel.com> References: <1392662333-25470-1-git-send-email-kirill.shutemov@linux.intel.com> <20140218175900.8CF90E0090@blue.fi.intel.com> <20140218180730.C2552E0090@blue.fi.intel.com> Date: Tue, 18 Feb 2014 10:28:11 -0800 X-Google-Sender-Auth: MmAbS7BB0-nF0kid9GWt6Lx9Idc Message-ID: Subject: Re: [RFC, PATCHv2 0/2] mm: map few pages around fault address if they are in page cache From: Linus Torvalds To: "Kirill A. Shutemov" Cc: Andrew Morton , Mel Gorman , Rik van Riel , Andi Kleen , Matthew Wilcox , Dave Hansen , Alexander Viro , Dave Chinner , linux-mm , linux-fsdevel , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 18, 2014 at 10:07 AM, Kirill A. Shutemov wrote: > > Patch is wrong. Correct one is below. Hmm. I don't hate this. Looking through it, it's fairly simple conceptually, and the code isn't that complex either. I can live with this. I think it's a bit odd how you pass both "max_pgoff" and "nr_pages" to the fault-around function, though. In fact, I'd consider that a bug. Passing in "FAULT_AROUND_PAGES" is just wrong, since the code cannot - and in fact *must* not - actually fault in that many pages, since the starting/ending address can be limited by other things. So I think that part of the code is bogus. You need to remove nr_pages, because any use of it is just incorrect. I don't think it can actually matter, since the max_pgoff checks are more restrictive, but if you think it can matter please explain how and why it wouldn't be a major bug? Apart from that, I'd really like to see numbers for different ranges of FAULT_AROUND_ORDER, because I think 5 is pretty high, but on the whole I don't find this horrible, and you still lock the page so it doesn't involve any new rules. I'm not hugely happy with another raw radix-tree user, but it's not horrible. Btw, is the "radix_tree_deref_retry(page) -> goto restart" really necessary? I'd be almost more inclined to just make it just do a "break;" to break out of the loop and stop doing anything clever at all. IOW, from a quick look there's a couple of small details I don't like that look odd, but .. Linus -- 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/