From: "NeilBrown" <neilb@suse.de>
To: "Wei Yang" <richard.weiyang@gmail.com>
Cc: kuba@kernel.org, gregkh@linuxfoundation.org,
mojha@codeaurora.org, jkosina@suse.cz,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] hashtable: remove a redundant check in hash_for_each_xxx()
Date: Thu, 07 Oct 2021 11:50:22 +1100 [thread overview]
Message-ID: <163356782206.31063.3710696596883334978@noble.neil.brown.name> (raw)
In-Reply-To: <20211007003058.uj35ekwibbrxqzku@master>
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>
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);\
next prev parent reply other threads:[~2021-10-07 0:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-06 15:21 [PATCH] hashtable: remove a redundant check in hash_for_each_xxx() Wei Yang
2021-10-06 15:29 ` Greg KH
2021-10-06 21:16 ` NeilBrown
2021-10-07 0:30 ` Wei Yang
2021-10-07 0:50 ` NeilBrown [this message]
2021-10-07 23:40 ` Wei Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=163356782206.31063.3710696596883334978@noble.neil.brown.name \
--to=neilb@suse.de \
--cc=gregkh@linuxfoundation.org \
--cc=jkosina@suse.cz \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mojha@codeaurora.org \
--cc=richard.weiyang@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).