Commit 279758f8 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
Browse files

rhashtable: Add rht_ptr_rcu and improve rht_ptr 



This patch moves common code between rht_ptr and rht_ptr_exclusive
into __rht_ptr.  It also adds a new helper rht_ptr_rcu exclusively
for the RCU case.  This way rht_ptr becomes a lock-only construct
so we can use the lighter rcu_dereference_protected primitive.

Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent af649352

include/linux/rhashtable.h

+18 −18
Original line number Diff line number Diff line
@@ -352,37 +352,38 @@ static inline void rht_unlock(struct bucket_table *tbl, 
static inline struct rhash_head __rcu *__rht_ptr(

	struct rhash_lock_head *const *bkt)

{

	return (struct rhash_head __rcu *)((unsigned long)*bkt & ~BIT(0));

	return (struct rhash_head __rcu *)

		((unsigned long)*bkt & ~BIT(0) ?:

		 (unsigned long)RHT_NULLS_MARKER(bkt));

}



/*

 * Where 'bkt' is a bucket and might be locked:

 *   rht_ptr() dereferences that pointer and clears the lock bit.

 *   rht_ptr_rcu() dereferences that pointer and clears the lock bit.

 *   rht_ptr() dereferences in a context where the bucket is locked.

 *   rht_ptr_exclusive() dereferences in a context where exclusive

 *            access is guaranteed, such as when destroying the table.

 */

static inline struct rhash_head *rht_ptr_rcu(

	struct rhash_lock_head *const *bkt)

{

	struct rhash_head __rcu *p = __rht_ptr(bkt);



	return rcu_dereference(p);

}



static inline struct rhash_head *rht_ptr(

	struct rhash_lock_head *const *bkt,

	struct bucket_table *tbl,

	unsigned int hash)

{

	struct rhash_head __rcu *p = __rht_ptr(bkt);



	if (!p)

		return RHT_NULLS_MARKER(bkt);



	return rht_dereference_bucket_rcu(p, tbl, hash);

	return rht_dereference_bucket(__rht_ptr(bkt), tbl, hash);

}



static inline struct rhash_head *rht_ptr_exclusive(

	struct rhash_lock_head *const *bkt)

{

	struct rhash_head __rcu *p = __rht_ptr(bkt);



	if (!p)

		return RHT_NULLS_MARKER(bkt);



	return rcu_dereference_protected(p, 1);

	return rcu_dereference_protected(__rht_ptr(bkt), 1);

}



static inline void rht_assign_locked(struct rhash_lock_head **bkt,
@@ -509,7 +510,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
 */

#define rht_for_each_rcu(pos, tbl, hash)			\

	for (({barrier(); }),					\

	     pos = rht_ptr(rht_bucket(tbl, hash), tbl, hash);	\

	     pos = rht_ptr_rcu(rht_bucket(tbl, hash));		\

	     !rht_is_a_nulls(pos);				\

	     pos = rcu_dereference_raw(pos->next))
@@ -546,8 +547,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
 */

#define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member)		   \

	rht_for_each_entry_rcu_from(tpos, pos,				   \

				    rht_ptr(rht_bucket(tbl, hash),	   \

					    tbl, hash),			   \

				    rht_ptr_rcu(rht_bucket(tbl, hash)),	   \

				    tbl, hash, member)



/**
@@ -603,7 +603,7 @@ restart: 
	hash = rht_key_hashfn(ht, tbl, key, params);

	bkt = rht_bucket(tbl, hash);

	do {

		rht_for_each_rcu_from(he, rht_ptr(bkt, tbl, hash), tbl, hash) {

		rht_for_each_rcu_from(he, rht_ptr_rcu(bkt), tbl, hash) {

			if (params.obj_cmpfn ?

			    params.obj_cmpfn(&arg, rht_obj(ht, he)) :

			    rhashtable_compare(&arg, rht_obj(ht, he)))

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