diff options
| author | Andrea Arcangeli <aarcange@redhat.com> | 2010-08-02 20:40:46 +0200 |
|---|---|---|
| committer | Andrea Arcangeli <aarcange@redhat.com> | 2010-08-02 18:43:04 +0000 |
| commit | 5e075da490ca5ba85b520134ca42640a18f6edf5 (patch) | |
| tree | 98d4446d4c0c975e5ab75f6c3f4f378b929f0e97 | |
| parent | 213c1ddbdb137e0d21fda824a67402d2109e1958 (diff) | |
root anon vma use root
Always use anon_vma->root pointer instead of anon_vma_chain.prev.
Also optimize the map-paths, if a mapping is already established no need to
overwrite it with root anon-vma list, we can keep the more finegrined anon-vma
and skip the overwrite: see the PageAnon check in !exclusive case. This is also
the optimization that hidden the ksm bug as this tends to make
ksm_might_need_to_copy skip the copy, but only the proper fix to
ksm_might_need_to_copy guarantees not triggering the ksm bug unless ksm is in
use. this is an optimization only...
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
| -rw-r--r-- | mm/rmap.c | 23 |
1 files changed, 7 insertions, 16 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index bc665c218406..8fbb312b0e0e 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -208,7 +208,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) */ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) { - struct anon_vma_chain *avc, *root_avc; + struct anon_vma_chain *avc; struct anon_vma *anon_vma; /* Don't bother if the parent process has no anon_vma here. */ @@ -230,14 +230,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) if (!avc) goto out_error_free_anon_vma; - /* - * Get the root anon_vma on the list by depending on the ordering - * of the same_vma list setup by previous invocations of anon_vma_fork. - * The root anon_vma will always be referenced by the last item - * in the anon_vma_chain list. - */ - root_avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma); - anon_vma->root = root_avc->anon_vma; + anon_vma->root = pvma->anon_vma->root; /* * With KSM refcounts, an anon_vma can stay around longer than the * process it belongs to. The root anon_vma needs to be pinned @@ -768,15 +761,13 @@ static void __page_set_anon_rmap(struct page *page, * If the page isn't exclusively mapped into this vma, * we must use the _oldest_ possible anon_vma for the * page mapping! - * - * So take the last AVC chain entry in the vma, which is - * the deepest ancestor, and use the anon_vma from that. */ if (!exclusive) { - struct anon_vma_chain *avc; - avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma); - anon_vma = avc->anon_vma; - } + if (PageAnon(page)) + return; + anon_vma = anon_vma->root; + } else + BUG_ON(PageAnon(page)); anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; page->mapping = (struct address_space *) anon_vma; |