Re: [PATCH] mm: fix NR_ISOLATED_[ANON|FILE] mismatch

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

On Wed, Sep 19, 2012 at 3:45 AM, Minchan Kim <minchan@kernel.org> wrote:
> When I looked at zone stat mismatch problem, I found
> migrate_to_node doesn't decrease NR_ISOLATED_[ANON|FILE]
> if check_range fails.
>
> It can make system hang out.
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Christoph Lameter <cl@linux.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
>  mm/mempolicy.c |   16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3d64b36..6bf0860 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -953,16 +953,16 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>
>         vma = check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
>                         flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> -       if (IS_ERR(vma))
> -               return PTR_ERR(vma);
> -
> -       if (!list_empty(&pagelist)) {
> +       if (IS_ERR(vma)) {
> +               err = PTR_ERR(vma);
> +               goto out;
> +       }
> +       if (!list_empty(&pagelist))
>                 err = migrate_pages(&pagelist, new_node_page, dest,
>                                                         false, MIGRATE_SYNC);
> -               if (err)
> -                       putback_lru_pages(&pagelist);
> -       }
> -
> +out:
> +       if (err)
> +               putback_lru_pages(&pagelist);

Good catch!
This is a regression since following commit. So, I doubt we need
all or nothing semantics. Can we revert it instead? (and probably
we need more kind comment for preventing an accident)


commit 0def08e3acc2c9c934e4671487029aed52202d42
Author: Vasiliy Kulikov <segooon@gmail.com>
Date:   Tue Oct 26 14:21:32 2010 -0700

    mm/mempolicy.c: check return code of check_range

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