On 29.04.22 17:15, Christian Borntraeger wrote:
> there are cases that trigger a 2nd shadow event for the same
> vmaddr/raddr combination. (prefix changes, reboots, some known races)
> This will increase memory usages and it will result in long latencies
> when cleaning up, e.g. on shutdown. To avoid cases with a list that has
> hundreds of identical raddrs we check existing entries at insert time.
> As this measurably reduces the list length this will be faster than
> traversing the list at shutdown time.
>
> In the long run several places will be optimized to create less entries
> and a shrinker might be necessary.
>
> Fixes: 4be130a08420 ("s390/mm: add shadow gmap support")
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
> ---
> arch/s390/mm/gmap.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 69c08d966fda..0fc0c26a71f2 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -1185,12 +1185,19 @@ static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
> struct gmap_rmap *rmap)
> {
> void __rcu **slot;
> + struct gmap_rmap *temp;
>
> BUG_ON(!gmap_is_shadow(sg));
> slot = radix_tree_lookup_slot(&sg->host_to_rmap, vmaddr >> PAGE_SHIFT);
> if (slot) {
> rmap->next = radix_tree_deref_slot_protected(slot,
> &sg->guest_table_lock);
> + for (temp = rmap->next; temp; temp = temp->next) {
> + if (temp->raddr == rmap->raddr) {
> + kfree(rmap);
> + return;
> + }
> + }
> radix_tree_replace_slot(&sg->host_to_rmap, slot, rmap);
> } else {
> rmap->next = NULL;
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
