On 07/27/2013 12:18 AM, Cyrill Gorcunov wrote:
> Andy reported that if file page get reclaimed we loose soft-dirty bit
> if it was there, so save _PAGE_BIT_SOFT_DIRTY bit when page address
> get encoded into pte entry. Thus when #pf happens on such non-present
> pte we can restore it back.
>
> Reported-by: Andy Lutomirski <l...@amacapital.net>
> Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org>
> Cc: Pavel Emelyanov <xe...@parallels.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Matt Mackall <m...@selenic.com>
> Cc: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com>
> Cc: Marcelo Tosatti <mtosa...@redhat.com>
> Cc: KOSAKI Motohiro <kosaki.motoh...@gmail.com>
> Cc: Stephen Rothwell <s...@canb.auug.org.au>
> ---
> @@ -57,17 +57,25 @@ static int install_file_pte(struct mm_st
> unsigned long addr, unsigned long pgoff, pgprot_t prot)
> {
> int err = -ENOMEM;
> - pte_t *pte;
> + pte_t *pte, ptfile;
> spinlock_t *ptl;
>
> pte = get_locked_pte(mm, addr, &ptl);
> if (!pte)
> goto out;
>
> - if (!pte_none(*pte))
> + ptfile = pgoff_to_pte(pgoff);
> +
> + if (!pte_none(*pte)) {
> +#ifdef CONFIG_MEM_SOFT_DIRTY
> + if (pte_present(*pte) &&
> + pte_soft_dirty(*pte))
I think there's no need in wrapping every such if () inside #ifdef CONFIG_...,
since the pte_soft_dirty() routine itself would be 0 for non-soft-dirty case
and compiler would optimize this code out.
> + pte_file_mksoft_dirty(ptfile);
> +#endif
> zap_pte(mm, vma, addr, pte);
> + }
>
> - set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
> + set_pte_at(mm, addr, pte, ptfile);
> /*
> * We don't need to run update_mmu_cache() here because the "file pte"
> * being installed by install_file_pte() is not a real pte - it's a
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