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SubjectRe: [PATCH] rhashtable: detect when object movement between tables might have invalidated a lookup
On Thu, Nov 15, 2018 at 10:32:13AM +1100, NeilBrown wrote:
>
> +#define RHT_NULLS_MARKER(ptr) \
> + ((void *)NULLS_MARKER(((unsigned long) (ptr)) >> 1))
> #define INIT_RHT_NULLS_HEAD(ptr) \
> - ((ptr) = (typeof(ptr)) NULLS_MARKER(0))
> + ((ptr) = RHT_NULLS_MARKER(&(ptr)))

Why are you shifting this by one?

> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index 30526afa8343..852ffa5160f1 100644
> --- a/lib/rhashtable.c
> +++ b/lib/rhashtable.c
> @@ -1179,8 +1179,7 @@ struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
> unsigned int hash)
> {
> const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
> - static struct rhash_head __rcu *rhnull =
> - (struct rhash_head __rcu *)NULLS_MARKER(0);
> + static struct rhash_head __rcu *rhnull;

I don't understand why you can't continue to do NULLS_MARKER(0) or
RHT_NULLS_MARKER(0).

Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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