Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755662AbZIPGWc (ORCPT ); Wed, 16 Sep 2009 02:22:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752782AbZIPGWa (ORCPT ); Wed, 16 Sep 2009 02:22:30 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:57549 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751804AbZIPGW3 (ORCPT ); Wed, 16 Sep 2009 02:22:29 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 16 Sep 2009 15:20:21 +0900 From: KAMEZAWA Hiroyuki To: Hugh Dickins Cc: Andrew Morton , Ralf Baechle , KOSAKI Motohiro , Linus Torvalds , Nick Piggin , Rik van Riel , Mel Gorman , Minchan Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 3/4] mm: ZERO_PAGE without PTE_SPECIAL Message-Id: <20090916152021.f76a3721.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5501 Lines: 158 On Tue, 15 Sep 2009 21:37:20 +0100 (BST) Hugh Dickins wrote: > Reinstate anonymous use of ZERO_PAGE to all architectures, not just > to those which __HAVE_ARCH_PTE_SPECIAL: as suggested by Nick Piggin. > > Contrary to how I'd imagined it, there's nothing ugly about this, just > a zero_pfn test built into one or another block of vm_normal_page(). > > But the MIPS ZERO_PAGE-of-many-colours case demands is_zero_pfn() and > my_zero_pfn() inlines. Reinstate its mremap move_pte() shuffling of > ZERO_PAGEs we did from 2.6.17 to 2.6.19? Not unless someone shouts > for that: it would have to take vm_flags to weed out some cases. > > Signed-off-by: Hugh Dickins Thank you. I like this way. Reviewed-by: KAMEZAWA Hiroyuki > --- > I've not built and tested the actual MIPS case, just hacked up x86 > definitions to simulate it; had to drop the static from zero_pfn. > > arch/mips/include/asm/pgtable.h | 14 +++++++++++ > mm/memory.c | 36 ++++++++++++++++++++---------- > 2 files changed, 39 insertions(+), 11 deletions(-) > > --- mm2/arch/mips/include/asm/pgtable.h 2009-09-09 23:13:59.000000000 +0100 > +++ mm3/arch/mips/include/asm/pgtable.h 2009-09-15 17:32:19.000000000 +0100 > @@ -76,6 +76,20 @@ extern unsigned long zero_page_mask; > #define ZERO_PAGE(vaddr) \ > (virt_to_page((void *)(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask)))) > > +#define is_zero_pfn is_zero_pfn > +static inline int is_zero_pfn(unsigned long pfn) > +{ > + extern unsigned long zero_pfn; > + unsigned long offset_from_zero_pfn = pfn - zero_pfn; > + return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT); > +} > + > +#define my_zero_pfn my_zero_pfn > +static inline unsigned long my_zero_pfn(unsigned long addr) > +{ > + return page_to_pfn(ZERO_PAGE(addr)); > +} > + > extern void paging_init(void); > > /* > --- mm2/mm/memory.c 2009-09-14 16:34:37.000000000 +0100 > +++ mm3/mm/memory.c 2009-09-15 17:32:19.000000000 +0100 > @@ -107,7 +107,7 @@ static int __init disable_randmaps(char > } > __setup("norandmaps", disable_randmaps); > > -static unsigned long zero_pfn __read_mostly; > +unsigned long zero_pfn __read_mostly; > > /* > * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init() > @@ -455,6 +455,20 @@ static inline int is_cow_mapping(unsigne > return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; > } > > +#ifndef is_zero_pfn > +static inline int is_zero_pfn(unsigned long pfn) > +{ > + return pfn == zero_pfn; > +} > +#endif > + > +#ifndef my_zero_pfn > +static inline unsigned long my_zero_pfn(unsigned long addr) > +{ > + return zero_pfn; > +} > +#endif > + > /* > * vm_normal_page -- This function gets the "struct page" associated with a pte. > * > @@ -512,7 +526,7 @@ struct page *vm_normal_page(struct vm_ar > goto check_pfn; > if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) > return NULL; > - if (pfn != zero_pfn) > + if (!is_zero_pfn(pfn)) > print_bad_pte(vma, addr, pte, NULL); > return NULL; > } > @@ -534,6 +548,8 @@ struct page *vm_normal_page(struct vm_ar > } > } > > + if (is_zero_pfn(pfn)) > + return NULL; > check_pfn: > if (unlikely(pfn > highest_memmap_pfn)) { > print_bad_pte(vma, addr, pte, NULL); > @@ -1161,7 +1177,7 @@ struct page *follow_page(struct vm_area_ > page = vm_normal_page(vma, address, pte); > if (unlikely(!page)) { > if ((flags & FOLL_DUMP) || > - pte_pfn(pte) != zero_pfn) > + !is_zero_pfn(pte_pfn(pte))) > goto bad_page; > page = pte_page(pte); > } > @@ -1444,10 +1460,6 @@ struct page *get_dump_page(unsigned long > if (__get_user_pages(current, current->mm, addr, 1, > FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1) > return NULL; > - if (page == ZERO_PAGE(0)) { > - page_cache_release(page); > - return NULL; > - } > flush_cache_page(vma, addr, page_to_pfn(page)); > return page; > } > @@ -1630,7 +1642,8 @@ int vm_insert_mixed(struct vm_area_struc > * If we don't have pte special, then we have to use the pfn_valid() > * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must* > * refcount the page if pfn_valid is true (hence insert_page rather > - * than insert_pfn). > + * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP > + * without pte special, it would there be refcounted as a normal page. > */ > if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) { > struct page *page; > @@ -2098,7 +2111,7 @@ gotten: > if (unlikely(anon_vma_prepare(vma))) > goto oom; > > - if (pte_pfn(orig_pte) == zero_pfn) { > + if (is_zero_pfn(pte_pfn(orig_pte))) { > new_page = alloc_zeroed_user_highpage_movable(vma, address); > if (!new_page) > goto oom; > @@ -2613,8 +2626,9 @@ static int do_anonymous_page(struct mm_s > spinlock_t *ptl; > pte_t entry; > > - if (HAVE_PTE_SPECIAL && !(flags & FAULT_FLAG_WRITE)) { > - entry = pte_mkspecial(pfn_pte(zero_pfn, vma->vm_page_prot)); > + if (!(flags & FAULT_FLAG_WRITE)) { > + entry = pte_mkspecial(pfn_pte(my_zero_pfn(address), > + vma->vm_page_prot)); > ptl = pte_lockptr(mm, pmd); > spin_lock(ptl); > if (!pte_none(*page_table)) > -- 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/