From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e2.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m4EIXGRo021393 for ; Wed, 14 May 2008 14:33:16 -0400 Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m4EIXG5x149632 for ; Wed, 14 May 2008 14:33:16 -0400 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m4EIXF0G031434 for ; Wed, 14 May 2008 14:33:16 -0400 Subject: Re: [patch 2/2]: introduce fast_gup From: Dave Kleikamp In-Reply-To: <20080422094629.GC23770@wotan.suse.de> References: <20080328025455.GA8083@wotan.suse.de> <20080328030023.GC8083@wotan.suse.de> <1208857356.7115.218.camel@twins> <20080422094629.GC23770@wotan.suse.de> Content-Type: text/plain Date: Wed, 14 May 2008 13:33:14 -0500 Message-Id: <1210789994.6377.21.camel@norville.austin.ibm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Peter Zijlstra , Andrew Morton , axboe@kernel.dk, linux-mm@kvack.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org List-ID: On Tue, 2008-04-22 at 11:46 +0200, Nick Piggin wrote: > On Tue, Apr 22, 2008 at 11:42:36AM +0200, Peter Zijlstra wrote: > > On Fri, 2008-03-28 at 04:00 +0100, Nick Piggin wrote: > > > > > +static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, > > > + unsigned long end, int write, struct page **pages, int *nr) > > > +{ > > > + unsigned long mask, result; > > > + pte_t *ptep; > > > + > > > + result = _PAGE_PRESENT|_PAGE_USER; > > > + if (write) > > > + result |= _PAGE_RW; > > > + mask = result | _PAGE_SPECIAL; > > > + > > > + ptep = pte_offset_map(&pmd, addr); > > > + do { > > > + /* > > > + * XXX: careful. On 3-level 32-bit, the pte is 64 bits, and > > > + * we need to make sure we load the low word first, then the > > > + * high. This means _PAGE_PRESENT should be clear if the high > > > + * word was not valid. Currently, the C compiler can issue > > > + * the loads in any order, and I don't know of a wrapper > > > + * function that will do this properly, so it is broken on > > > + * 32-bit 3-level for the moment. > > > + */ > > > + pte_t pte = *ptep; > > > + struct page *page; > > > + > > > + if ((pte_val(pte) & mask) != result) > > > + return 0; > > > > This return path fails to unmap the pmd. > > Ah good catch. As you can see I haven't done any highmem testing ;) > Which I will do so before sending upstream. Which will be when? We'd really like to see this in mainline as soon as possible and in -mm in the meanwhile. Thanks, Shaggy -- David Kleikamp IBM Linux Technology Center -- 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