Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932078AbZKJVv4 (ORCPT ); Tue, 10 Nov 2009 16:51:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758283AbZKJVvz (ORCPT ); Tue, 10 Nov 2009 16:51:55 -0500 Received: from mk-filter-4-a-1.mail.uk.tiscali.com ([212.74.100.55]:13844 "EHLO mk-filter-4-a-1.mail.uk.tiscali.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758268AbZKJVvy (ORCPT ); Tue, 10 Nov 2009 16:51:54 -0500 X-Trace: 284012177/mk-filter-4.mail.uk.tiscali.com/B2C/$b2c-THROTTLED-DYNAMIC/b2c-CUSTOMER-DYNAMIC-IP/79.69.44.180/None/hugh.dickins@tiscali.co.uk X-SBRS: None X-RemoteIP: 79.69.44.180 X-IP-MAIL-FROM: hugh.dickins@tiscali.co.uk X-SMTP-AUTH: X-MUA: X-IP-BHB: Once X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AjkFAMdv+UpPRSy0/2dsb2JhbACBTt01hD4E X-IronPort-AV: E=Sophos;i="4.44,718,1249254000"; d="scan'208";a="284012177" Date: Tue, 10 Nov 2009 21:51:46 +0000 (GMT) From: Hugh Dickins X-X-Sender: hugh@sister.anvils To: Andrew Morton cc: Izik Eidus , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 1/6] mm: define PAGE_MAPPING_FLAGS In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6473 Lines: 173 At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set in page->mapping, with the higher bits a pointer to the anon_vma; and have defined PageKsm(page) as that with NULL anon_vma. But KSM swapping will need to store a pointer there: so in preparation for that, now define PAGE_MAPPING_FLAGS as the low two bits, including PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some other use for the bit emerges). Declare page_rmapping(page) to return the pointer part of page->mapping, and page_anon_vma(page) to return the anon_vma pointer when that's what it is. Use these in a few appropriate places: notably, unuse_vma() has been testing page->mapping, but is better to be testing page_anon_vma() (cases may be added in which flag bits are set without any pointer). Signed-off-by: Hugh Dickins --- include/linux/ksm.h | 5 +++-- include/linux/mm.h | 17 ++++++++++++++++- include/linux/rmap.h | 8 ++++++++ mm/migrate.c | 11 ++++------- mm/rmap.c | 7 +++---- mm/swapfile.c | 2 +- 6 files changed, 35 insertions(+), 15 deletions(-) --- mm0/include/linux/ksm.h 2009-09-28 00:28:38.000000000 +0100 +++ mm1/include/linux/ksm.h 2009-11-04 10:52:45.000000000 +0000 @@ -38,7 +38,8 @@ static inline void ksm_exit(struct mm_st */ static inline int PageKsm(struct page *page) { - return ((unsigned long)page->mapping == PAGE_MAPPING_ANON); + return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) == + (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); } /* @@ -47,7 +48,7 @@ static inline int PageKsm(struct page *p static inline void page_add_ksm_rmap(struct page *page) { if (atomic_inc_and_test(&page->_mapcount)) { - page->mapping = (void *) PAGE_MAPPING_ANON; + page->mapping = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); __inc_zone_page_state(page, NR_ANON_PAGES); } } --- mm0/include/linux/mm.h 2009-11-02 12:32:34.000000000 +0000 +++ mm1/include/linux/mm.h 2009-11-04 10:52:45.000000000 +0000 @@ -620,13 +620,22 @@ void page_address_init(void); /* * On an anonymous page mapped into a user virtual memory area, * page->mapping points to its anon_vma, not to a struct address_space; - * with the PAGE_MAPPING_ANON bit set to distinguish it. + * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h. + * + * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled, + * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit; + * and then page->mapping points, not to an anon_vma, but to a private + * structure which KSM associates with that merged page. See ksm.h. + * + * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used. * * Please note that, confusingly, "page_mapping" refers to the inode * address_space which maps the page from disk; whereas "page_mapped" * refers to user virtual address space into which the page is mapped. */ #define PAGE_MAPPING_ANON 1 +#define PAGE_MAPPING_KSM 2 +#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM) extern struct address_space swapper_space; static inline struct address_space *page_mapping(struct page *page) @@ -644,6 +653,12 @@ static inline struct address_space *page return mapping; } +/* Neutral page->mapping pointer to address_space or anon_vma or other */ +static inline void *page_rmapping(struct page *page) +{ + return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS); +} + static inline int PageAnon(struct page *page) { return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0; --- mm0/include/linux/rmap.h 2009-09-28 00:28:39.000000000 +0100 +++ mm1/include/linux/rmap.h 2009-11-04 10:52:45.000000000 +0000 @@ -39,6 +39,14 @@ struct anon_vma { #ifdef CONFIG_MMU +static inline struct anon_vma *page_anon_vma(struct page *page) +{ + if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != + PAGE_MAPPING_ANON) + return NULL; + return page_rmapping(page); +} + static inline void anon_vma_lock(struct vm_area_struct *vma) { struct anon_vma *anon_vma = vma->anon_vma; --- mm0/mm/migrate.c 2009-11-02 12:32:34.000000000 +0000 +++ mm1/mm/migrate.c 2009-11-04 10:52:45.000000000 +0000 @@ -172,17 +172,14 @@ static void remove_anon_migration_ptes(s { struct anon_vma *anon_vma; struct vm_area_struct *vma; - unsigned long mapping; - - mapping = (unsigned long)new->mapping; - - if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) - return; /* * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. */ - anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); + anon_vma = page_anon_vma(new); + if (!anon_vma) + return; + spin_lock(&anon_vma->lock); list_for_each_entry(vma, &anon_vma->head, anon_vma_node) --- mm0/mm/rmap.c 2009-11-02 12:32:34.000000000 +0000 +++ mm1/mm/rmap.c 2009-11-04 10:52:45.000000000 +0000 @@ -203,7 +203,7 @@ struct anon_vma *page_lock_anon_vma(stru rcu_read_lock(); anon_mapping = (unsigned long) page->mapping; - if (!(anon_mapping & PAGE_MAPPING_ANON)) + if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) goto out; if (!page_mapped(page)) goto out; @@ -248,8 +248,7 @@ vma_address(struct page *page, struct vm unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) { if (PageAnon(page)) { - if ((void *)vma->anon_vma != - (void *)page->mapping - PAGE_MAPPING_ANON) + if (vma->anon_vma != page_anon_vma(page)) return -EFAULT; } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { if (!vma->vm_file || @@ -512,7 +511,7 @@ int page_referenced(struct page *page, referenced++; *vm_flags = 0; - if (page_mapped(page) && page->mapping) { + if (page_mapped(page) && page_rmapping(page)) { if (PageAnon(page)) referenced += page_referenced_anon(page, mem_cont, vm_flags); --- mm0/mm/swapfile.c 2009-11-04 10:21:17.000000000 +0000 +++ mm1/mm/swapfile.c 2009-11-04 10:52:45.000000000 +0000 @@ -937,7 +937,7 @@ static int unuse_vma(struct vm_area_stru unsigned long addr, end, next; int ret; - if (page->mapping) { + if (page_anon_vma(page)) { addr = page_address_in_vma(page, vma); if (addr == -EFAULT) return 0; -- 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/