RE: amusing SLUB compaction bug when CC_OPTIMIZE_FOR_SIZE

David Laight
2022-09-29T11:53:29Z

> -static void rcu_free_slab(struct rcu_head *h)
> +/*
> + * rcu_free_slab() must be __aligned(4) because its address is saved
> + * in the rcu_head field, which coincides with page->mapping, which
> + * causes trouble if compaction mistakes it for PAGE_MAPPING_MOVABLE.
> + */
> +__aligned(4) static void rcu_free_slab(struct rcu_head *h)
> {
> struct slab *slab = container_of(h, struct slab, rcu_head);
>

Isn't that going to cause grief with options that align
functions on 16/32byte boundaries when adding space for
'other stuff'?

David

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