Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755904AbYKKNWp (ORCPT ); Tue, 11 Nov 2008 08:22:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755917AbYKKNWT (ORCPT ); Tue, 11 Nov 2008 08:22:19 -0500 Received: from mx2.redhat.com ([66.187.237.31]:33429 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755897AbYKKNWS (ORCPT ); Tue, 11 Nov 2008 08:22:18 -0500 From: Izik Eidus To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, kvm@vger.kernel.org, aarcange@redhat.com, chrisw@redhat.com, avi@redhat.com, Izik Eidus Subject: [PATCH 2/4] Add replace_page(), change the mapping of pte from one page into another Date: Tue, 11 Nov 2008 15:21:39 +0200 Message-Id: <1226409701-14831-3-git-send-email-ieidus@redhat.com> In-Reply-To: <1226409701-14831-2-git-send-email-ieidus@redhat.com> References: <1226409701-14831-1-git-send-email-ieidus@redhat.com> <1226409701-14831-2-git-send-email-ieidus@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3389 Lines: 119 From: Izik Eidus this function is needed in cases you want to change the userspace virtual mapping into diffrent physical page, KSM need this for merging the identical pages. this function is working by removing the oldpage from the rmap and calling put_page on it, and by setting the virtual address pte to point into the new page. (note that the new page (the page that we change the pte to map to) cannot be anonymous page) Signed-off-by: Izik Eidus --- include/linux/mm.h | 3 ++ mm/memory.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+), 0 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index ffee2f7..4da7fa8 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1207,6 +1207,9 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn); +int replace_page(struct vm_area_struct *vma, struct page *oldpage, + struct page *newpage, pte_t orig_pte, pgprot_t prot); + struct page *follow_page(struct vm_area_struct *, unsigned long address, unsigned int foll_flags); #define FOLL_WRITE 0x01 /* check pte is writable */ diff --git a/mm/memory.c b/mm/memory.c index 164951c..b2c542c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1472,6 +1472,74 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, } EXPORT_SYMBOL(vm_insert_mixed); +/** + * replace _page - replace the pte mapping related to vm area between two pages + * (from oldpage to newpage) + * NOTE: you should take into consideration the impact on the VM when replacing + * anonymous pages with kernel non swappable pages. + */ +int replace_page(struct vm_area_struct *vma, struct page *oldpage, + struct page *newpage, pte_t orig_pte, pgprot_t prot) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *ptep; + spinlock_t *ptl; + unsigned long addr; + int ret; + + BUG_ON(PageAnon(newpage)); + + ret = -EFAULT; + addr = page_address_in_vma(oldpage, vma); + if (addr == -EFAULT) + goto out; + + pgd = pgd_offset(mm, addr); + if (!pgd_present(*pgd)) + goto out; + + pud = pud_offset(pgd, addr); + if (!pud_present(*pud)) + goto out; + + pmd = pmd_offset(pud, addr); + if (!pmd_present(*pmd)) + goto out; + + ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!ptep) + goto out; + + if (!pte_same(*ptep, orig_pte)) { + pte_unmap_unlock(ptep, ptl); + goto out; + } + + ret = 0; + get_page(newpage); + page_add_file_rmap(newpage); + + flush_cache_page(vma, addr, pte_pfn(*ptep)); + ptep_clear_flush(vma, addr, ptep); + set_pte_at(mm, addr, ptep, mk_pte(newpage, prot)); + + page_remove_rmap(oldpage, vma); + if (PageAnon(oldpage)) { + dec_mm_counter(mm, anon_rss); + inc_mm_counter(mm, file_rss); + } + put_page(oldpage); + + pte_unmap_unlock(ptep, ptl); + +out: + return ret; +} +EXPORT_SYMBOL(replace_page); + /* * maps a range of physical memory into the requested pages. the old * mappings are removed. any references to nonexistent pages results -- 1.6.0.3 -- 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/