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[PATCH] mm: ptd_alloc take ptlock

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Second step in pushing down the page_table_lock.  Remove the temporary
bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not
to hold page_table_lock, whether it's on init_mm or a user mm; take
page_table_lock internally to check if a racing task already allocated.

Convert their callers from common code.  But avoid coming back to change them
again later: instead of moving the spin_lock(&mm->page_table_lock) down,
switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which
encapsulate the mapping+locking and unlocking+unmapping together, and in the
end may use alternatives to the mm page_table_lock itself.

These callers all hold mmap_sem (some exclusively, some not), so at no level
can a page table be whipped away from beneath them; and pte_alloc uses the
"atomic" pmd_present to test whether it needs to allocate.  It appears that on
all arches we can safely descend without page_table_lock.

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 18:16:23 -07:00
committed by Linus Torvalds
parent 1bb3630e89
commit c74df32c72
7 changed files with 90 additions and 135 deletions
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48
mm/fremap.c
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@@ -63,23 +63,20 @@ int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
pud_t *pud;
pgd_t *pgd;
pte_t pte_val;
spinlock_t *ptl;
BUG_ON(vma->vm_flags & VM_RESERVED);
pgd = pgd_offset(mm, addr);
spin_lock(&mm->page_table_lock);
pud = pud_alloc(mm, pgd, addr);
if (!pud)
goto err_unlock;
goto out;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
goto err_unlock;
pte = pte_alloc_map(mm, pmd, addr);
goto out;
pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
goto err_unlock;
goto out;
/*
* This page may have been truncated. Tell the
@@ -89,10 +86,10 @@ int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
inode = vma->vm_file->f_mapping->host;
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (!page->mapping || page->index >= size)
goto err_unlock;
goto unlock;
err = -ENOMEM;
if (page_mapcount(page) > INT_MAX/2)
goto err_unlock;
goto unlock;
if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
inc_mm_counter(mm, file_rss);
@@ -101,17 +98,15 @@ int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
set_pte_at(mm, addr, pte, mk_pte(page, prot));
page_add_file_rmap(page);
pte_val = *pte;
pte_unmap(pte);
update_mmu_cache(vma, addr, pte_val);
err = 0;
err_unlock:
spin_unlock(&mm->page_table_lock);
unlock:
pte_unmap_unlock(pte, ptl);
out:
return err;
}
EXPORT_SYMBOL(install_page);
/*
* Install a file pte to a given virtual memory address, release any
* previously existing mapping.
@@ -125,23 +120,20 @@ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
pud_t *pud;
pgd_t *pgd;
pte_t pte_val;
spinlock_t *ptl;
BUG_ON(vma->vm_flags & VM_RESERVED);
pgd = pgd_offset(mm, addr);
spin_lock(&mm->page_table_lock);
pud = pud_alloc(mm, pgd, addr);
if (!pud)
goto err_unlock;
goto out;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
goto err_unlock;
pte = pte_alloc_map(mm, pmd, addr);
goto out;
pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
goto err_unlock;
goto out;
if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
update_hiwater_rss(mm);
@@ -150,17 +142,13 @@ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
pte_val = *pte;
pte_unmap(pte);
update_mmu_cache(vma, addr, pte_val);
spin_unlock(&mm->page_table_lock);
return 0;
err_unlock:
spin_unlock(&mm->page_table_lock);
pte_unmap_unlock(pte, ptl);
err = 0;
out:
return err;
}
/***
* sys_remap_file_pages - remap arbitrary pages of a shared backing store
* file within an existing vma.