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[PATCH] mm: rmap with inner ptlock 

rmap's page_check_address descend without page_table_lock.  First just
pte_offset_map in case there's no pte present worth locking for, then take
page_table_lock for the full check, and pass ptl back to caller in the same
style as pte_offset_map_lock.  __xip_unmap, page_referenced_one and
try_to_unmap_one use pte_unmap_unlock.  try_to_unmap_cluster also.

page_check_address reformatted to avoid progressive indentation.  No use is
made of its one error code, return NULL when it fails.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Hugh Dickins 2005-10-29 18:16:31 -07:00 committed by Linus Torvalds
parent 67b02f119d
commit c0718806cf
3 changed files with 60 additions and 65 deletions
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4
include/linux/rmap.h
View File

@ -95,8 +95,8 @@ int try_to_unmap(struct page *);
/*
* Called from mm/filemap_xip.c to unmap empty zero page
*/
pte_t *page_check_address(struct page *, struct mm_struct *, unsigned long);
pte_t *page_check_address(struct page *, struct mm_struct *,
unsigned long, spinlock_t **);
/*
* Used by swapoff to help locate where page is expected in vma.

12
mm/filemap_xip.c
View File

@ -174,6 +174,7 @@ __xip_unmap (struct address_space * mapping,
unsigned long address;
pte_t *pte;
pte_t pteval;
spinlock_t *ptl;
struct page *page;
spin_lock(&mapping->i_mmap_lock);
@ -183,20 +184,15 @@ __xip_unmap (struct address_space * mapping,
((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
page = ZERO_PAGE(address);
/*
* We need the page_table_lock to protect us from page faults,
* munmap, fork, etc...
*/
pte = page_check_address(page, mm, address);
if (!IS_ERR(pte)) {
pte = page_check_address(page, mm, address, &ptl);
if (pte) {
/* Nuke the page table entry. */
flush_cache_page(vma, address, pte_pfn(*pte));
pteval = ptep_clear_flush(vma, address, pte);
page_remove_rmap(page);
dec_mm_counter(mm, file_rss);
BUG_ON(pte_dirty(pteval));
pte_unmap(pte);
spin_unlock(&mm->page_table_lock);
pte_unmap_unlock(pte, ptl);
page_cache_release(page);
}
}

109
mm/rmap.c
View File

@ -247,34 +247,41 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
* On success returns with mapped pte and locked mm->page_table_lock.
*/
pte_t *page_check_address(struct page *page, struct mm_struct *mm,
unsigned long address)
unsigned long address, spinlock_t **ptlp)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
spinlock_t *ptl;
/*
* 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 (likely(pgd_present(*pgd))) {
pud = pud_offset(pgd, address);
if (likely(pud_present(*pud))) {
pmd = pmd_offset(pud, 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);
}
}
if (!pgd_present(*pgd))
return NULL;
pud = pud_offset(pgd, address);
if (!pud_present(*pud))
return NULL;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
return NULL;
pte = pte_offset_map(pmd, address);
/* Make a quick check before getting the lock */
if (!pte_present(*pte)) {
pte_unmap(pte);
return NULL;
}
spin_unlock(&mm->page_table_lock);
return ERR_PTR(-ENOENT);
ptl = &mm->page_table_lock;
spin_lock(ptl);
if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
*ptlp = ptl;
return pte;
}
pte_unmap_unlock(pte, ptl);
return NULL;
}
/*
@ -287,28 +294,28 @@ static int page_referenced_one(struct page *page,
struct mm_struct *mm = vma->vm_mm;
unsigned long address;
pte_t *pte;
spinlock_t *ptl;
int referenced = 0;
address = vma_address(page, vma);
if (address == -EFAULT)
goto out;
pte = page_check_address(page, mm, address);
if (!IS_ERR(pte)) {
if (ptep_clear_flush_young(vma, address, pte))
referenced++;
pte = page_check_address(page, mm, address, &ptl);
if (!pte)
goto out;
/* Pretend the page is referenced if the task has the
swap token and is in the middle of a page fault. */
if (mm != current->mm && !ignore_token &&
has_swap_token(mm) &&
rwsem_is_locked(&mm->mmap_sem))
referenced++;
if (ptep_clear_flush_young(vma, address, pte))
referenced++;
(*mapcount)--;
pte_unmap(pte);
spin_unlock(&mm->page_table_lock);
}
/* Pretend the page is referenced if the task has the
swap token and is in the middle of a page fault. */
if (mm != current->mm && !ignore_token && has_swap_token(mm) &&
rwsem_is_locked(&mm->mmap_sem))
referenced++;
(*mapcount)--;
pte_unmap_unlock(pte, ptl);
out:
return referenced;
}
@ -507,14 +514,15 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
unsigned long address;
pte_t *pte;
pte_t pteval;
spinlock_t *ptl;
int ret = SWAP_AGAIN;
address = vma_address(page, vma);
if (address == -EFAULT)
goto out;
pte = page_check_address(page, mm, address);
if (IS_ERR(pte))
pte = page_check_address(page, mm, address, &ptl);
if (!pte)
goto out;
/*
@ -564,8 +572,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
page_cache_release(page);
out_unmap:
pte_unmap(pte);
spin_unlock(&mm->page_table_lock);
pte_unmap_unlock(pte, ptl);
out:
return ret;
}
@ -599,19 +606,14 @@ static void try_to_unmap_cluster(unsigned long cursor,
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte, *original_pte;
pte_t *pte;
pte_t pteval;
spinlock_t *ptl;
struct page *page;
unsigned long address;
unsigned long end;
unsigned long pfn;
/*
* We need the page_table_lock to protect us from page faults,
* munmap, fork, etc...
*/
spin_lock(&mm->page_table_lock);
address = (vma->vm_start + cursor) & CLUSTER_MASK;
end = address + CLUSTER_SIZE;
if (address < vma->vm_start)
@ -621,22 +623,22 @@ static void try_to_unmap_cluster(unsigned long cursor,
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
goto out_unlock;
return;
pud = pud_offset(pgd, address);
if (!pud_present(*pud))
goto out_unlock;
return;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
goto out_unlock;
return;
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
/* Update high watermark before we lower rss */
update_hiwater_rss(mm);
for (original_pte = pte = pte_offset_map(pmd, address);
address < end; pte++, address += PAGE_SIZE) {
for (; address < end; pte++, address += PAGE_SIZE) {
if (!pte_present(*pte))
continue;
@ -669,10 +671,7 @@ static void try_to_unmap_cluster(unsigned long cursor,
dec_mm_counter(mm, file_rss);
(*mapcount)--;
}
pte_unmap(original_pte);
out_unlock:
spin_unlock(&mm->page_table_lock);
pte_unmap_unlock(pte - 1, ptl);
}
static int try_to_unmap_anon(struct page *page)