From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f47.google.com (mail-bk0-f47.google.com [209.85.214.47]) by kanga.kvack.org (Postfix) with ESMTP id A2AD46B0035 for ; Thu, 28 Nov 2013 12:42:31 -0500 (EST) Received: by mail-bk0-f47.google.com with SMTP id mx12so3870197bkb.6 for ; Thu, 28 Nov 2013 09:42:30 -0800 (PST) Received: from mail-la0-x234.google.com (mail-la0-x234.google.com [2a00:1450:4010:c03::234]) by mx.google.com with ESMTPS id aq1si9139357bkc.237.2013.11.28.09.42.30 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 28 Nov 2013 09:42:30 -0800 (PST) Received: by mail-la0-f52.google.com with SMTP id y1so4308033lam.39 for ; Thu, 28 Nov 2013 09:42:30 -0800 (PST) Date: Thu, 28 Nov 2013 18:41:57 +0100 From: Vladimir Murzin Subject: Re: [PATCH]mm/vmalloc: interchage the implementation of vmalloc_to_{pfn,page} Message-ID: <20131128174152.GA2258@hp530> References: <20131128162913.GA4234@lcx> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20131128162913.GA4234@lcx> Sender: owner-linux-mm@kvack.org List-ID: To: Jianyu Zhan Cc: linux-mm@kvack.org, akpm@linux-foundation.org, iamjoonsoo.kim@lge.com, zhangyanfei@cn.fujitsu.com, liwanp@linux.vnet.ibm.com, rientjes@google.com, linux-kernel@vger.kernel.org On Fri, Nov 29, 2013 at 12:29:13AM +0800, Jianyu Zhan wrote: > Currently we are implementing vmalloc_to_pfn() as a wrapper of > vmalloc_to_page(), which is implemented as follow: > > 1. walks the page talbes to generates the corresponding pfn, > 2. then wraps the pfn to struct page, > 3. returns it. > > And vmalloc_to_pfn() re-wraps the vmalloc_to_page() to get the pfn. > > This seems too circuitous, so this patch reverses the way: > implementing the vmalloc_to_page() as a wrapper of vmalloc_to_pfn(). > This makes vmalloc_to_pfn() and vmalloc_to_page() slightly effective. Any numbers for efficiency? > > No functional change. > > Signed-off-by: Jianyu Zhan > --- > mm/vmalloc.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 0fdf968..a335e21 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -220,12 +220,12 @@ int is_vmalloc_or_module_addr(const void *x) > } > > /* > - * Walk a vmap address to the struct page it maps. > + * Walk a vmap address to the physical pfn it maps to. > */ > -struct page *vmalloc_to_page(const void *vmalloc_addr) > +unsigned long vmalloc_to_pfn(const void *vmalloc_addr) > { > unsigned long addr = (unsigned long) vmalloc_addr; > - struct page *page = NULL; > + unsigned long pfn; uninitialized pfn will lead to a bug. > pgd_t *pgd = pgd_offset_k(addr); > > /* > @@ -244,23 +244,23 @@ struct page *vmalloc_to_page(const void *vmalloc_addr) > ptep = pte_offset_map(pmd, addr); > pte = *ptep; > if (pte_present(pte)) > - page = pte_page(pte); > + pfn = pte_page(pte); page_to_pfn is missed here. Have you ever tested there is no functional changes? Vladimir > pte_unmap(ptep); > } > } > } > - return page; > + return pfn; > } > -EXPORT_SYMBOL(vmalloc_to_page); > +EXPORT_SYMBOL(vmalloc_to_pfn); > > /* > - * Map a vmalloc()-space virtual address to the physical page frame number. > + * Map a vmalloc()-space virtual address to the struct page. > */ > -unsigned long vmalloc_to_pfn(const void *vmalloc_addr) > +struct page *vmalloc_to_page(const void *vmalloc_addr) > { > - return page_to_pfn(vmalloc_to_page(vmalloc_addr)); > + return pfn_to_page(vmalloc_to_pfn(vmalloc_addr)); > } > -EXPORT_SYMBOL(vmalloc_to_pfn); > +EXPORT_SYMBOL(vmalloc_to_page); > > > /*** Global kva allocator ***/ > > -- > 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 -- 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