On Thu 17-11-16 14:11:32, Johannes Weiner wrote:
> When the shadow page shrinker tries to reclaim a radix tree node but
> finds it in an unexpected state - it should contain no pages, and
> non-zero shadow entries - there is no need to kill the executing task
> or even the entire system. Warn about the invalid state, then leave
> that tree node be. Simply don't put it back on the shadow LRU for
> future reclaim and move on.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> mm/workingset.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/mm/workingset.c b/mm/workingset.c
> index 617475f529f4..3cfc61d84a52 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -418,23 +418,27 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
> * no pages, so we expect to be able to remove them all and
> * delete and free the empty node afterwards.
> */
> - BUG_ON(!workingset_node_shadows(node));
> - BUG_ON(workingset_node_pages(node));
> -
> + if (WARN_ON_ONCE(!workingset_node_shadows(node)))
> + goto out_invalid;
> + if (WARN_ON_ONCE(workingset_node_pages(node)))
> + goto out_invalid;
> for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
> if (node->slots[i]) {
> - BUG_ON(!radix_tree_exceptional_entry(node->slots[i]));
> + if (WARN_ON_ONCE(!radix_tree_exceptional_entry(node->slots[i])))
> + goto out_invalid;
> + if (WARN_ON_ONCE(!mapping->nrexceptional))
> + goto out_invalid;
> node->slots[i] = NULL;
> workingset_node_shadows_dec(node);
> - BUG_ON(!mapping->nrexceptional);
> mapping->nrexceptional--;
> }
> }
> - BUG_ON(workingset_node_shadows(node));
> + if (WARN_ON_ONCE(workingset_node_shadows(node)))
> + goto out_invalid;
> inc_node_state(page_pgdat(virt_to_page(node)), WORKINGSET_NODERECLAIM);
> - if (!__radix_tree_delete_node(&mapping->page_tree, node))
> - BUG();
> + __radix_tree_delete_node(&mapping->page_tree, node);
>
> +out_invalid:
> spin_unlock(&mapping->tree_lock);
> ret = LRU_REMOVED_RETRY;
> out:
> --
> 2.10.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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