On Tue, Aug 06, 2013 at 05:43:38PM +0900, Joonsoo Kim wrote:
> If we allocate anon_vma_chain before starting to link, we can reduce
> the lock hold time. This patch implement it.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index c2f51cb..1603f64 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -240,18 +240,21 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
> {
> struct anon_vma_chain *avc, *pavc;
> struct anon_vma *root = NULL;
> + LIST_HEAD(avc_list);
> +
> + list_for_each_entry(pavc, &src->anon_vma_chain, same_vma) {
> + avc = anon_vma_chain_alloc(GFP_KERNEL);
> + if (unlikely(!avc))
> + goto enomem_failure;
> +
> + list_add_tail(&avc->same_vma, &avc_list);
> + }
>
> list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
> struct anon_vma *anon_vma;
>
> - avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
> - if (unlikely(!avc)) {
> - unlock_anon_vma_root(root);
> - root = NULL;
> - avc = anon_vma_chain_alloc(GFP_KERNEL);
> - if (!avc)
> - goto enomem_failure;
> - }
> + avc = list_entry((&avc_list)->next, typeof(*avc), same_vma);
list_first_entry() please
> + list_del(&avc->same_vma);
> anon_vma = pavc->anon_vma;
> root = lock_anon_vma_root(root, anon_vma);
> anon_vma_chain_link(dst, avc, anon_vma);
> @@ -259,8 +262,11 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
> unlock_anon_vma_root(root);
> return 0;
>
> - enomem_failure:
> - unlink_anon_vmas(dst);
> +enomem_failure:
> + list_for_each_entry_safe(avc, pavc, &avc_list, same_vma) {
> + list_del(&avc->same_vma);
> + anon_vma_chain_free(avc);
> + }
> return -ENOMEM;
> }
Otherwise, looks good.
Thanks!
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