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SubjectRe: [PATCH] hashtable: remove a redundant check in hash_for_each_xxx()
On Thu, Oct 07, 2021 at 11:50:22AM +1100, NeilBrown wrote:
>On Thu, 07 Oct 2021, Wei Yang wrote:
>>
>> Here is a draft patch based on you comment:
>>
>> diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
>> index f6c666730b8c..2ff4cb5e6a22 100644
>> --- a/include/linux/hashtable.h
>> +++ b/include/linux/hashtable.h
>> @@ -116,6 +116,13 @@ static inline void hash_del_rcu(struct hlist_node *node)
>> hlist_del_init_rcu(node);
>> }
>>
>> +/**
>> + * Note: the following three hash_for_each[_xxx] helpers introduce a new loop
>> + * command that is constructed from 2 nested loops. It is safe to 'break' out
>> + * of this loop even though it is a two nested loops. The 'obj == NULL' test
>> + * ensures that when the inner loop is broken, the outer loop will break too.
>> + */
>> +
>> /**
>> * hash_for_each - iterate over a hashtable
>> * @name: hashtable to iterate
>>
>>
>> If you feel good, I would like to add
>>
>> Sugguested-by: NeilBrown <neilb@suse.de>
>
>That's definitely an improvement.
>
>I'd probably put it in the kernel-doc comment for hash_for_each,
>then in the other two just put the "it is safe" bit. Something like
>the following. But I don't feel strongly about it.
>I'm happy to say
> Reviewed-by: NeilBrown <neilb@suse.de>
>

Thanks for your detailed instruction :-)

>for your patch.
>
>Thanks,
>NeilBrown
>
>
>diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
>index f6c666730b8c..61db940c9501 100644
>--- a/include/linux/hashtable.h
>+++ b/include/linux/hashtable.h
>@@ -122,6 +122,10 @@ static inline void hash_del_rcu(struct hlist_node *node)
> * @bkt: integer to use as bucket loop cursor
> * @obj: the type * to use as a loop cursor for each entry
> * @member: the name of the hlist_node within the struct
>+ *
>+ * Note: It is safe to 'break' out of this loop even though it is a two
>+ * nested loops. The 'obj == NULL' test ensures that when the inner loop
>+ * is broken, the outer loop will break too.
> */
> #define hash_for_each(name, bkt, obj, member) \
> for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
>@@ -134,6 +138,8 @@ static inline void hash_del_rcu(struct hlist_node *node)
> * @bkt: integer to use as bucket loop cursor
> * @obj: the type * to use as a loop cursor for each entry
> * @member: the name of the hlist_node within the struct
>+ *
>+ * It is safe to 'break' out of this loop.
> */
> #define hash_for_each_rcu(name, bkt, obj, member) \
> for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\
>@@ -148,6 +154,8 @@ static inline void hash_del_rcu(struct hlist_node *node)
> * @tmp: a &struct hlist_node used for temporary storage
> * @obj: the type * to use as a loop cursor for each entry
> * @member: the name of the hlist_node within the struct
>+ *
>+ * It is safe to 'break' out of this loop.
> */
> #define hash_for_each_safe(name, bkt, tmp, obj, member) \
> for ((bkt) = 0, obj = NULL; obj == NULL && (bkt) < HASH_SIZE(name);\

--
Wei Yang
Help you, Help me

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