Re: [PATCH v3 1/2] mm/list_lru.c: fix list_lru_count_node() to be race free

Vladimir Davydov
2017-06-28T17:19:07Z

On Wed, Jun 28, 2017 at 11:37:23AM +0530, Sahitya Tummala wrote:
> list_lru_count_node() iterates over all memcgs to get
> the total number of entries on the node but it can race with
> memcg_drain_all_list_lrus(), which migrates the entries from
> a dead cgroup to another. This can return incorrect number of
> entries from list_lru_count_node().
>
> Fix this by keeping track of entries per node and simply return
> it in list_lru_count_node().
>
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> ---
> include/linux/list_lru.h | 1 +
> mm/list_lru.c | 14 ++++++--------
> 2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> index cb0ba9f..eff61bc 100644
> --- a/include/linux/list_lru.h
> +++ b/include/linux/list_lru.h
> @@ -44,6 +44,7 @@ struct list_lru_node {
> /* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
> struct list_lru_memcg *memcg_lrus;
> #endif
> + long nr_count;

'nr_count' sounds awkward. I think it should be called 'nr_items'.

Other than that, looks good to me.