From: NeilBrown <neilb@suse.com>
To: Thomas Graf <tgraf@suug.ch>,
Herbert Xu <herbert@gondor.apana.org.au>,
Tom Herbert <tom@quantonium.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] rhashtable: add rhashtable_walk_last_seen()
Date: Fri, 06 Jul 2018 17:11:32 +1000 [thread overview]
Message-ID: <153086109260.2825.1459722786871837620.stgit@noble> (raw)
In-Reply-To: <153086101070.2825.6850140624411927465.stgit@noble>
rhashtable_walk_last_seen() returns the object returned by
the previous rhashtable_walk_next(), providing it is still in the
table (or was during this grace period).
This works even if rhashtable_walk_stop() and rhashtable_talk_start()
have been called since the last rhashtable_walk_next().
If there have been no calls to rhashtable_walk_next(), or if the
object is gone from the table, then NULL is returned.
This can usefully be used in a seq_file ->start() function.
If the pos is the same as was returned by the last ->next() call,
then rhashtable_walk_last_seen() can be used to re-establish the
current location in the table. If it returns NULL, then
rhashtable_walk_next() should be used.
Signed-off-by: NeilBrown <neilb@suse.com>
---
include/linux/rhashtable.h | 1 +
lib/rhashtable.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 31 insertions(+)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 657e37ae314c..d63b472e9d50 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -248,6 +248,7 @@ static inline void rhashtable_walk_start(struct rhashtable_iter *iter)
void *rhashtable_walk_next(struct rhashtable_iter *iter);
void *rhashtable_walk_peek(struct rhashtable_iter *iter);
+void *rhashtable_walk_last_seen(struct rhashtable_iter *iter);
void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
void rhashtable_free_and_destroy(struct rhashtable *ht,
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 36f97d0c69ce..2d0227822262 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -947,6 +947,36 @@ void *rhashtable_walk_peek(struct rhashtable_iter *iter)
}
EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
+/**
+ * rhashtable_walk_last_seen - Return the previously returned object, if available
+ * @iter: Hash table iterator
+ *
+ * If rhashtable_walk_next() has previously been called and the object
+ * it returned is still in the hash table, that object is returned again,
+ * otherwise %NULL is returned.
+ *
+ * If the recent rhashtable_walk_next() call was since the most recent
+ * rhashtable_walk_start() call then the returned object may not, strictly
+ * speaking, still be in the table. It will be safe to dereference.
+ *
+ * Note that the iterator is not changed.
+ */
+void *rhashtable_walk_last_seen(struct rhashtable_iter *iter)
+{
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+
+ if (!p)
+ return NULL;
+ if (!iter->p_is_unsafe || ht->rhlist)
+ return p;
+ rht_for_each_rcu(p, iter->walker.tbl, iter->slot)
+ if (p == iter->p)
+ return p;
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_last_seen);
+
/**
* rhashtable_walk_stop - Finish a hash table walk
* @iter: Hash table iterator
next prev parent reply other threads:[~2018-07-06 7:13 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-06 7:11 [PATCH 0/3] rhashtable: replace rhashtable_walk_peek implementation NeilBrown
2018-07-06 7:11 ` [PATCH 3/3] rhashtable: implement rhashtable_walk_peek() using rhashtable_walk_last_seen() NeilBrown
2018-07-06 7:11 ` [PATCH 1/3] rhashtable: further improve stability of rhashtable_walk NeilBrown
2018-07-06 8:24 ` kbuild test robot
2018-07-06 9:50 ` NeilBrown
2018-07-06 8:59 ` Paolo Abeni
2018-07-06 9:55 ` NeilBrown
2018-07-06 10:12 ` Paolo Abeni
2018-07-06 9:25 ` kbuild test robot
2018-12-05 3:51 ` [PATCH net-next] " NeilBrown
2018-12-07 5:39 ` Herbert Xu
2018-12-09 22:50 ` NeilBrown
2018-12-11 5:17 ` Herbert Xu
2018-12-12 0:02 ` NeilBrown
2018-12-12 5:46 ` Herbert Xu
2018-12-12 6:41 ` NeilBrown
2018-12-12 8:00 ` Herbert Xu
2018-12-12 8:49 ` NeilBrown
2018-12-13 1:43 ` Herbert Xu
2018-12-13 3:48 ` NeilBrown
2018-12-13 8:47 ` Herbert Xu
2018-07-06 7:11 ` NeilBrown [this message]
2018-07-10 23:55 ` [PATCH 2/3] rhashtable: add rhashtable_walk_last_seen() David Miller
2018-07-15 23:58 ` NeilBrown
2018-07-10 23:55 ` [PATCH 0/3] rhashtable: replace rhashtable_walk_peek implementation David Miller
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