From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756272AbaHHNjk (ORCPT ); Fri, 8 Aug 2014 09:39:40 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:57022 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752801AbaHHNjj (ORCPT ); Fri, 8 Aug 2014 09:39:39 -0400 Message-ID: <53E4D312.5000601@codeaurora.org> Date: Fri, 08 Aug 2014 19:09:30 +0530 From: Chintan Pandya User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111108 Thunderbird/3.1.16 MIME-Version: 1.0 To: "Sha, Ruibin" CC: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "a.p.zijlstra@chello.nl" , "mgorman@suse.de" , "mingo@redhat.com" , "Zhang, Yanmin" , "He, Bo" Subject: Re: [PATCH] export the function kmap_flush_unused. References: <3C85A229999D6B4A89FA64D4680BA6142C7DFA@SHSMSX101.ccr.corp.intel.com> In-Reply-To: <3C85A229999D6B4A89FA64D4680BA6142C7DFA@SHSMSX101.ccr.corp.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/08/2014 02:46 PM, Sha, Ruibin wrote: > export the function kmap_flush_unused. > > Scenario: When graphic driver need high memory spece, we use alloc_pages() > to allocate. But if the allocated page has just been > mapped in the KMAP space(like first kmap then kunmap) and > no flush page happened on PKMAP, the page virtual address is > not NULL.Then when we get that page and set page attribute like > set_memory_uc and set_memory_wc, we hit error. Could you explain your scenario with more details ? set_memory_* should be applied on mapped address. And in attempt to map your page (which was just kmap and kunmap'ed), it will overwrite the previous mappings. Moreover, in my view, kmap_flush_unused is just helping us in keeping the cache clean for kmap virtual addresses if they are unmapped. Is it serving any more purpose here ? > > fix: For that scenario,when we get the allocated page and its virtual > address is not NULL, we would like first flush that page. > So need export that function kmap_flush_unused. > > Signed-off-by: sha, ruibin > > --- > mm/highmem.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/highmem.c b/mm/highmem.c > index b32b70c..511299b 100644 > --- a/mm/highmem.c > +++ b/mm/highmem.c > @@ -156,6 +156,7 @@ void kmap_flush_unused(void) > flush_all_zero_pkmaps(); > unlock_kmap(); > } > +EXPORT_SYMBOL(kmap_flush_unused); This symbol is already extern'ed. Is it not sufficient for your case ? > > static inline unsigned long map_new_virtual(struct page *page) > { > -- > 1.7.9.5 > > Best Regards > > --------------------------------------------------------------- > > Sha, Rui bin ( Robin ) > > +86 13817890945 > > Android System Integration Shanghai > -- Chintan Pandya QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation