diff options
author | Hugh Dickins | 2005-10-29 18:16:23 -0700 |
---|---|---|
committer | Linus Torvalds | 2005-10-29 21:40:40 -0700 |
commit | c74df32c724a1652ad8399b4891bb02c9d43743a (patch) | |
tree | 5a79d56fdcf7dc2053a277dbf6db7c3b339e9659 /mm/mremap.c | |
parent | 1bb3630e89cb8a7b3d3807629c20c5bad88290ff (diff) |
[PATCH] mm: ptd_alloc take ptlock
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>
Diffstat (limited to 'mm/mremap.c')
-rw-r--r-- | mm/mremap.c | 27 |
1 files changed, 9 insertions, 18 deletions
diff --git a/mm/mremap.c b/mm/mremap.c index 616facc3d28a..8de77b632a20 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -28,9 +28,6 @@ static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) pud_t *pud; pmd_t *pmd; - /* - * We don't need page_table_lock: we have mmap_sem exclusively. - */ pgd = pgd_offset(mm, addr); if (pgd_none_or_clear_bad(pgd)) return NULL; @@ -50,25 +47,20 @@ static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; pud_t *pud; - pmd_t *pmd = NULL; + pmd_t *pmd; - /* - * We do need page_table_lock: because allocators expect that. - */ - spin_lock(&mm->page_table_lock); pgd = pgd_offset(mm, addr); pud = pud_alloc(mm, pgd, addr); if (!pud) - goto out; + return NULL; pmd = pmd_alloc(mm, pud, addr); if (!pmd) - goto out; + return NULL; if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr)) - pmd = NULL; -out: - spin_unlock(&mm->page_table_lock); + return NULL; + return pmd; } @@ -80,6 +72,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, struct address_space *mapping = NULL; struct mm_struct *mm = vma->vm_mm; pte_t *old_pte, *new_pte, pte; + spinlock_t *old_ptl; if (vma->vm_file) { /* @@ -95,9 +88,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, new_vma->vm_truncate_count = 0; } - spin_lock(&mm->page_table_lock); - old_pte = pte_offset_map(old_pmd, old_addr); - new_pte = pte_offset_map_nested(new_pmd, new_addr); + old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); + new_pte = pte_offset_map_nested(new_pmd, new_addr); for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, new_pte++, new_addr += PAGE_SIZE) { @@ -110,8 +102,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, } pte_unmap_nested(new_pte - 1); - pte_unmap(old_pte - 1); - spin_unlock(&mm->page_table_lock); + pte_unmap_unlock(old_pte - 1, old_ptl); if (mapping) spin_unlock(&mapping->i_mmap_lock); } |