On Sat 28-02-15 14:01:46, Wang, Yalin wrote:
> This patch add ClearPageDirty() to clear AnonPage dirty flag,
> if not clear page dirty for this anon page, the page will never be
> treated as freeable. we also make sure the shared AnonPage is not
> freeable, we implement it by dirty all copyed AnonPage pte,
> so that make sure the Anonpage will not become freeable, unless
> all process which shared this page call madvise_free syscall.
I am not able to parse this text.
> Another change is that we also handle file map page,
> we just clear pte young bit for file map, this is useful,
> it can make reclaim patch move file pages into inactive
> lru list aggressively.
This doesn't belong to this patch. If file private mappings should allow
MADV_FREE is a separate topic and should be discussed independently.
>
> Signed-off-by: Yalin Wang <yalin.wang@xxxxxxxxxxxxxx>
> ---
> mm/madvise.c | 26 +++++++++++++++-----------
> mm/memory.c | 12 ++++++++++--
> 2 files changed, 25 insertions(+), 13 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 6d0fcb8..712756b 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -299,30 +299,38 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> page = vm_normal_page(vma, addr, ptent);
> if (!page)
> continue;
> + if (!PageAnon(page))
> + goto set_pte;
> + if (!trylock_page(page))
> + continue;
>
> if (PageSwapCache(page)) {
> - if (!trylock_page(page))
> - continue;
> -
> if (!try_to_free_swap(page)) {
> unlock_page(page);
> continue;
> }
> -
> - ClearPageDirty(page);
> - unlock_page(page);
> }
>
> /*
> + * we clear page dirty flag for AnonPage, no matter if this
> + * page is in swapcahce or not, AnonPage not in swapcache also set
> + * dirty flag sometimes, this happened when an AnonPage is removed
> + * from swapcahce by try_to_free_swap()
> + */
> + ClearPageDirty(page);
> + unlock_page(page);
> + /*
> * Some of architecture(ex, PPC) don't update TLB
> * with set_pte_at and tlb_remove_tlb_entry so for
> * the portability, remap the pte with old|clean
> * after pte clearing.
> */
> +set_pte:
> ptent = ptep_get_and_clear_full(mm, addr, pte,
> tlb->fullmm);
> ptent = pte_mkold(ptent);
> - ptent = pte_mkclean(ptent);
> + if (PageAnon(page))
> + ptent = pte_mkclean(ptent);
> set_pte_at(mm, addr, pte, ptent);
> tlb_remove_tlb_entry(tlb, pte, addr);
> }
> @@ -364,10 +372,6 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
> if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
> return -EINVAL;
>
> - /* MADV_FREE works for only anon vma at the moment */
> - if (vma->vm_file)
> - return -EINVAL;
> -
> start = max(vma->vm_start, start_addr);
> if (start >= vma->vm_end)
> return -EINVAL;
> diff --git a/mm/memory.c b/mm/memory.c
> index 8068893..3d949b3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -874,10 +874,18 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> if (page) {
> get_page(page);
> page_dup_rmap(page);
> - if (PageAnon(page))
> + if (PageAnon(page)) {
> + /*
> + * we dirty the copyed pte for anon page,
> + * this is useful for madvise_free_pte_range(),
> + * this can prevent shared anon page freed by madvise_free
> + * syscall
> + */
> + pte = pte_mkdirty(pte);
> rss[MM_ANONPAGES]++;
> - else
> + } else {
> rss[MM_FILEPAGES]++;
> + }
> }
>
> out_set_pte:
> --
> 2.2.2
> --
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--
Michal Hocko
SUSE Labs
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