RE: [PATCH 3/4] rhashtable: use bit_spin_locks to protect hash bucket.

From: David Laight
Date: Tue Apr 02 2019 - 06:10:34 EST

From: NeilBrown
> Sent: 02 April 2019 00:08
> This patch changes rhashtables to use a bit_spin_lock on BIT(1) of the
> bucket pointer to lock the hash chain for that bucket.
> To enhance type checking, a new struct is introduced to represent the
> pointer plus lock-bit
> that is stored in the bucket-table. This is "struct rhash_lock_head"
> and is empty. A pointer to this needs to be cast to either an
> unsigned lock, or a "struct rhash_head *" to be useful.
> Variables of this type are most often called "bkt".

Did you try using a union of the pointer and an 'unsigned long' ?
Should remove a lot of the casts.


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