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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2006-09-25 23:31:00 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-26 08:48:44 -0700 |
| commit | ee6a6457886a80415db209e87033b63f2b06558c (patch) | |
| tree | 227351bf31ccc6153879cc900c5d6a822832b645 /mm | |
| parent | e88dd6c11c5aef74d8b74a062767add53315533b (diff) | |
| download | lwn-ee6a6457886a80415db209e87033b63f2b06558c.tar.gz lwn-ee6a6457886a80415db209e87033b63f2b06558c.zip | |
[PATCH] mm: fixup do_wp_page()
Wrt. the recent modifications in do_wp_page() Hugh Dickins pointed out:
"I now realize it's right to the first order (normal case) and to the
second order (ptrace poke), but not to the third order (ptrace poke
anon page here to be COWed - perhaps can't occur without intervening
mprotects)."
This patch restores the old COW behaviour for anonymous pages.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-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')
| -rw-r--r-- | mm/memory.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/mm/memory.c b/mm/memory.c index dd7d7fc5ed60..65962534b4ed 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1467,11 +1467,21 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, goto gotten; /* - * Only catch write-faults on shared writable pages, read-only - * shared pages can get COWed by get_user_pages(.write=1, .force=1). + * Take out anonymous pages first, anonymous shared vmas are + * not dirty accountable. */ - if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == + if (PageAnon(old_page)) { + if (!TestSetPageLocked(old_page)) { + reuse = can_share_swap_page(old_page); + unlock_page(old_page); + } + } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED))) { + /* + * Only catch write-faults on shared writable pages, + * read-only shared pages can get COWed by + * get_user_pages(.write=1, .force=1). + */ if (vma->vm_ops && vma->vm_ops->page_mkwrite) { /* * Notify the address space that the page is about to @@ -1503,9 +1513,6 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, dirty_page = old_page; get_page(dirty_page); reuse = 1; - } else if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { - reuse = can_share_swap_page(old_page); - unlock_page(old_page); } if (reuse) { |