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Subject[PATCH]: 3/4 mm/rmap.c cleanup
mm/rmap.c:page_referenced_one() and mm/rmap.c:try_to_unmap_one() contain
identical code that

- takes mm->page_table_lock;

- drills through page tables;

- checks that correct pte is reached.

Coalesce this into page_check_address()

(Patch is for 2.6.10-rc2)

Signed-off-by: Nikita Danilov <nikita@clusterfs.com>

mm/rmap.c | 95 +++++++++++++++++++++++++++-----------------------------------
1 files changed, 42 insertions(+), 53 deletions(-)

diff -puN mm/rmap.c~rmap-cleanup mm/rmap.c
--- bk-linux/mm/rmap.c~rmap-cleanup 2004-11-21 17:01:03.038470288 +0300
+++ bk-linux-nikita/mm/rmap.c 2004-11-21 17:01:03.041469832 +0300
@@ -250,6 +250,34 @@ unsigned long page_address_in_vma(struct
}

/*
+ * Check that @page is mapped at @address into @mm.
+ *
+ * On success returns with mapped pte and locked mm->page_table_lock.
+ */
+static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
+ unsigned long address)
+{
+ pgd_t *pgd;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ spin_lock(&mm->page_table_lock);
+ pgd = pgd_offset(mm, address);
+ if (likely(pgd_present(*pgd))) {
+ pmd = pmd_offset(pgd, address);
+ if (likely(pmd_present(*pmd))) {
+ pte = pte_offset_map(pmd, address);
+ if (likely(pte_present(*pte) &&
+ page_to_pfn(page) == pte_pfn(*pte)))
+ return pte;
+ pte_unmap(pte);
+ }
+ }
+ spin_unlock(&mm->page_table_lock);
+ return ERR_PTR(-ENOENT);
+}
+
+/*
* Subfunctions of page_referenced: page_referenced_one called
* repeatedly from either page_referenced_anon or page_referenced_file.
*/
@@ -258,8 +286,6 @@ static int page_referenced_one(struct pa
{
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
- pgd_t *pgd;
- pmd_t *pmd;
pte_t *pte;
int referenced = 0;

@@ -269,35 +295,18 @@ static int page_referenced_one(struct pa
if (address == -EFAULT)
goto out;

- spin_lock(&mm->page_table_lock);
-
- pgd = pgd_offset(mm, address);
- if (!pgd_present(*pgd))
- goto out_unlock;
-
- pmd = pmd_offset(pgd, address);
- if (!pmd_present(*pmd))
- goto out_unlock;
-
- pte = pte_offset_map(pmd, address);
- if (!pte_present(*pte))
- goto out_unmap;
-
- if (page_to_pfn(page) != pte_pfn(*pte))
- goto out_unmap;
-
- if (ptep_clear_flush_young(vma, address, pte))
- referenced++;
-
- if (mm != current->mm && !ignore_token && has_swap_token(mm))
- referenced++;
+ pte = page_check_address(page, mm, address);
+ if (!IS_ERR(pte)) {
+ if (ptep_clear_flush_young(vma, address, pte))
+ referenced++;

- (*mapcount)--;
+ if (mm != current->mm && !ignore_token && has_swap_token(mm))
+ referenced++;

-out_unmap:
- pte_unmap(pte);
-out_unlock:
- spin_unlock(&mm->page_table_lock);
+ (*mapcount)--;
+ pte_unmap(pte);
+ spin_unlock(&mm->page_table_lock);
+ }
out:
return referenced;
}
@@ -501,8 +510,6 @@ static int try_to_unmap_one(struct page
{
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
- pgd_t *pgd;
- pmd_t *pmd;
pte_t *pte;
pte_t pteval;
int ret = SWAP_AGAIN;
@@ -513,26 +520,9 @@ static int try_to_unmap_one(struct page
if (address == -EFAULT)
goto out;

- /*
- * We need the page_table_lock to protect us from page faults,
- * munmap, fork, etc...
- */
- spin_lock(&mm->page_table_lock);
-
- pgd = pgd_offset(mm, address);
- if (!pgd_present(*pgd))
- goto out_unlock;
-
- pmd = pmd_offset(pgd, address);
- if (!pmd_present(*pmd))
- goto out_unlock;
-
- pte = pte_offset_map(pmd, address);
- if (!pte_present(*pte))
- goto out_unmap;
-
- if (page_to_pfn(page) != pte_pfn(*pte))
- goto out_unmap;
+ pte = page_check_address(page, mm, address);
+ if (IS_ERR(pte))
+
-
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