[PATCH 2/3] rhashtable: add rhashtable_walk_last_seen()
From: NeilBrown <hidden>
Date: 2018-07-06 07:13:49
Also in:
lkml
Subsystem:
library code, rhashtable, the rest · Maintainers:
Andrew Morton, Thomas Graf, Herbert Xu, Linus Torvalds
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 <redacted> --- 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