Re: [PATCH 1/3] rhashtable: further improve stability of rhashtable_walk

[kbuild test robot]

Hi NeilBrown,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net-next/master]
[also build test ERROR on next-20180705]
[cannot apply to linus/master linux-sof-driver/master v4.18-rc3]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/NeilBrown/rhashtable-replace-rhashtable_walk_peek-implementation/20180706-153705
config: i386-randconfig-x078-201826 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   In file included from ipc/util.c:66:0:
   include/linux/rhashtable.h: In function '__rhashtable_insert_fast':
>> include/linux/rhashtable.h:624:6: error: 'headp' undeclared (first use in this function); did you mean 'head'?
         headp = &head->next;
         ^~~~~
         head
   include/linux/rhashtable.h:624:6: note: each undeclared identifier is reported only once for each function it appears in

vim +624 include/linux/rhashtable.h

   570	
   571	/* Internal function, please use rhashtable_insert_fast() instead. This
   572	 * function returns the existing element already in hashes in there is a clash,
   573	 * otherwise it returns an error via ERR_PTR().
   574	 */
   575	static inline void *__rhashtable_insert_fast(
   576		struct rhashtable *ht, const void *key, struct rhash_head *obj,
   577		const struct rhashtable_params params, bool rhlist)
   578	{
   579		struct rhashtable_compare_arg arg = {
   580			.ht = ht,
   581			.key = key,
   582		};
   583		struct rhash_head __rcu **pprev;
   584		struct bucket_table *tbl;
   585		struct rhash_head *head;
   586		spinlock_t *lock;
   587		unsigned int hash;
   588		int elasticity;
   589		void *data;
   590	
   591		rcu_read_lock();
   592	
   593		tbl = rht_dereference_rcu(ht->tbl, ht);
   594		hash = rht_head_hashfn(ht, tbl, obj, params);
   595		lock = rht_bucket_lock(tbl, hash);
   596		spin_lock_bh(lock);
   597	
   598		if (unlikely(rcu_access_pointer(tbl->future_tbl))) {
   599	slow_path:
   600			spin_unlock_bh(lock);
   601			rcu_read_unlock();
   602			return rhashtable_insert_slow(ht, key, obj);
   603		}
   604	
   605		elasticity = RHT_ELASTICITY;
   606		pprev = rht_bucket_insert(ht, tbl, hash);
   607		data = ERR_PTR(-ENOMEM);
   608		if (!pprev)
   609			goto out;
   610	
   611		rht_for_each_continue(head, *pprev, tbl, hash) {
   612			struct rhlist_head *plist;
   613			struct rhlist_head *list;
   614	
   615			elasticity--;
   616			if (!key ||
   617			    (params.obj_cmpfn ?
   618			     params.obj_cmpfn(&arg, rht_obj(ht, head)) :
   619			     rhashtable_compare(&arg, rht_obj(ht, head)))) {
   620				if (rhlist) {
   621					pprev = &head->next;
   622				} else {
   623					if (head < obj)
 > 624						headp = &head->next;
   625				}
   626				continue;
   627			}
   628	
   629			data = rht_obj(ht, head);
   630	
   631			if (!rhlist)
   632				goto out;
   633	
   634	
   635			list = container_of(obj, struct rhlist_head, rhead);
   636			plist = container_of(head, struct rhlist_head, rhead);
   637	
   638			RCU_INIT_POINTER(list->next, plist);
   639			head = rht_dereference_bucket(head->next, tbl, hash);
   640			RCU_INIT_POINTER(list->rhead.next, head);
   641			rcu_assign_pointer(*pprev, obj);
   642	
   643			goto good;
   644		}
   645	
   646		if (elasticity <= 0)
   647			goto slow_path;
   648	
   649		data = ERR_PTR(-E2BIG);
   650		if (unlikely(rht_grow_above_max(ht, tbl)))
   651			goto out;
   652	
   653		if (unlikely(rht_grow_above_100(ht, tbl)))
   654			goto slow_path;
   655	
   656		head = rht_dereference_bucket(*pprev, tbl, hash);
   657	
   658		RCU_INIT_POINTER(obj->next, head);
   659		if (rhlist) {
   660			struct rhlist_head *list;
   661	
   662			list = container_of(obj, struct rhlist_head, rhead);
   663			RCU_INIT_POINTER(list->next, NULL);
   664		}
   665	
   666		rcu_assign_pointer(*pprev, obj);
   667	
   668		atomic_inc(&ht->nelems);
   669		if (rht_grow_above_75(ht, tbl))
   670			schedule_work(&ht->run_work);
   671	
   672	good:
   673		data = NULL;
   674	
   675	out:
   676		spin_unlock_bh(lock);
   677		rcu_read_unlock();
   678	
   679		return data;
   680	}
   681	

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