Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753313Ab3JDSdU (ORCPT ); Fri, 4 Oct 2013 14:33:20 -0400 Received: from cantor2.suse.de ([195.135.220.15]:42521 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751174Ab3JDSdT (ORCPT ); Fri, 4 Oct 2013 14:33:19 -0400 Date: Fri, 4 Oct 2013 20:33:15 +0200 From: Jan Kara To: "Marciniszyn, Mike" Cc: Jan Kara , LKML , "linux-mm@kvack.org" , infinipath , Roland Dreier , "linux-rdma@vger.kernel.org" Subject: Re: [PATCH 23/26] ib: Convert qib_get_user_pages() to get_user_pages_unlocked() Message-ID: <20131004183315.GA19557@quack.suse.cz> References: <1380724087-13927-1-git-send-email-jack@suse.cz> <1380724087-13927-24-git-send-email-jack@suse.cz> <32E1700B9017364D9B60AED9960492BC211B0176@FMSMSX107.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32E1700B9017364D9B60AED9960492BC211B0176@FMSMSX107.amr.corp.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1640 Lines: 36 On Fri 04-10-13 13:52:49, Marciniszyn, Mike wrote: > > Convert qib_get_user_pages() to use get_user_pages_unlocked(). This > > shortens the section where we hold mmap_sem for writing and also removes > > the knowledge about get_user_pages() locking from ipath driver. We also fix > > a bug in testing pinned number of pages when changing the code. > > > > This patch and the sibling ipath patch will nominally take the mmap_sem > twice where the old routine only took it once. This is a performance > issue. It will take mmap_sem only once during normal operation. Only if get_user_pages_unlocked() fail, we have to take mmap_sem again to undo the change of mm->pinned_vm. > Is the intent here to deprecate get_user_pages()? Well, as much as I'd like to, there are really places in mm code which need to call get_user_pages() while holding mmap_sem to be able to inspect corresponding vmas etc. So I want to reduce get_user_pages() use as much as possible but I'm not really hoping in completely removing it. > I agree, the old code's lock limit test is broke and needs to be fixed. > I like the elimination of the silly wrapper routine! > > Could the lock limit test be pushed into another version of the wrapper > so that there is only one set of mmap_sem transactions? I'm sorry, I don't understand what you mean here... Honza -- Jan Kara SUSE Labs, CR -- 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/