Commit 73bd1227 authored by Herbert Xu's avatar Herbert Xu Committed by Tejun Heo
Browse files

rhashtable: Restore insecure_elasticity toggle 



Some users of rhashtable cannot handle insertion failures, and
are happy to accept the consequences of a hash table that having
very long chains.

Restore the insecure_elasticity toggle for these users.  In
addition to disabling the chain length checks, this also removes
the emergency resize that would otherwise occur when the hash
table occupancy hits 100% (an async resize is still scheduled
at 75%).

Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 3cd8b194

include/linux/rhashtable-types.h

+2 −0
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg, 
 * @head_offset: Offset of rhash_head in struct to be hashed

 * @max_size: Maximum size while expanding

 * @min_size: Minimum size while shrinking

 * @insecure_elasticity: Set to true to disable chain length checks

 * @automatic_shrinking: Enable automatic shrinking of tables

 * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)

 * @obj_hashfn: Function to hash object
@@ -61,6 +62,7 @@ struct rhashtable_params { 
	u16			head_offset;

	unsigned int		max_size;

	u16			min_size;

	bool			insecure_elasticity;

	bool			automatic_shrinking;

	rht_hashfn_t		hashfn;

	rht_obj_hashfn_t	obj_hashfn;

include/linux/rhashtable.h

+3 −2
Original line number Diff line number Diff line
@@ -821,14 +821,15 @@ static __always_inline void *__rhashtable_insert_fast( 
		goto out;

	}



	if (elasticity <= 0)

	if (elasticity <= 0 && !params.insecure_elasticity)

		goto slow_path;



	data = ERR_PTR(-E2BIG);

	if (unlikely(rht_grow_above_max(ht, tbl)))

		goto out_unlock;



	if (unlikely(rht_grow_above_100(ht, tbl)))

	if (unlikely(rht_grow_above_100(ht, tbl)) &&

	    !params.insecure_elasticity)

		goto slow_path;



	/* Inserting at head of list makes unlocking free. */

lib/rhashtable.c

+3 −2
Original line number Diff line number Diff line
@@ -538,7 +538,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht, 
		return NULL;

	}



	if (elasticity <= 0)

	if (elasticity <= 0 && !ht->p.insecure_elasticity)

		return ERR_PTR(-EAGAIN);



	return ERR_PTR(-ENOENT);
@@ -568,7 +568,8 @@ static struct bucket_table *rhashtable_insert_one( 
	if (unlikely(rht_grow_above_max(ht, tbl)))

		return ERR_PTR(-E2BIG);



	if (unlikely(rht_grow_above_100(ht, tbl)))

	if (unlikely(rht_grow_above_100(ht, tbl)) &&

	    !ht->p.insecure_elasticity)

		return ERR_PTR(-EAGAIN);



	head = rht_ptr(bkt, tbl, hash);