From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 22 Apr 2008 11:46:29 +0200 From: Nick Piggin Subject: Re: [patch 2/2]: introduce fast_gup Message-ID: <20080422094629.GC23770@wotan.suse.de> References: <20080328025455.GA8083@wotan.suse.de> <20080328030023.GC8083@wotan.suse.de> <1208857356.7115.218.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1208857356.7115.218.camel@twins> Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Andrew Morton , shaggy@austin.ibm.com, axboe@kernel.dk, linux-mm@kvack.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org List-ID: 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. -- 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