[RFC][PATCH 2/5] add new exported function replace_page()

[RFC][PATCH 2/5] add new exported function replace_page()

[Izik Eidus]

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-- 
woof.


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>From c6fc21397e37481696723115cb1680f42661be48 Mon Sep 17 00:00:00 2001
From: Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
Date: Mon, 21 Jan 2008 17:04:45 +0200
Subject: [PATCH] memory.c: add new exported function replace_page()
 replace_page() - replace the pte mapping related to vm area between two pages
 (from oldpage to newpage)

Signed-off-by: Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
---
 include/linux/mm.h |    5 +++-
 mm/memory.c        |   60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1b7b95c..a311c25 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1094,7 +1094,10 @@ int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 			unsigned long pfn, unsigned long size, pgprot_t);
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn);
+		  unsigned long pfn);
+
+int replace_page(struct vm_area_struct *vma, struct page *oldpage,
+		 struct page *newpage, pgprot_t prot);
 
 struct page *follow_page(struct vm_area_struct *, unsigned long address,
 			unsigned int foll_flags);
diff --git a/mm/memory.c b/mm/memory.c
index 4bf0b6d..d8cb36b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2360,6 +2360,66 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
 }
 
+/**
+ * replace_page - replace the pte mapping related to vm area between two pages
+ * (from oldpage to newpage)
+ */
+int replace_page(struct vm_area_struct *vma, struct page *oldpage,
+		 struct page *newpage, 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(!PageLocked(oldpage));
+
+	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;
+
+	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_GPL(replace_page);
+
 
 /*
  * do_no_pfn() tries to create a new page mapping for a page without
-- 
1.5.3.6


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Re: [RFC][PATCH 2/5] add new exported function replace_page()

[Rik van Riel]

On Mon, 21 Jan 2008 18:10:50 +0200
Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:

> 

What prevents another CPU from freeing newpage while we run through
the start of replace_page() ?

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Re: [RFC][PATCH 2/5] add new exported function replace_page()

[Izik Eidus]

Rik van Riel wrote:
> On Mon, 21 Jan 2008 18:10:50 +0200
> Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>
>   
>
> What prevents another CPU from freeing newpage while we run through
> the start of replace_page() ?
>
>   
before calling to replace_page one have to call to get_page() and to do 
put_page() after it finished
this what i am doing in ksm.c

should i do it in diffrent way?

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