Messages in this thread Patch in this message | | | From | NeilBrown <> | Date | Tue, 12 Jun 2018 12:48:31 +1000 | Subject | [PATCH RFC v2] rhashtable: implement rhashtable_walk_peek() using rhashtable_walk_last_seen() |
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rhashtable_walk_last_seen() does most of the work that rhashtable_walk_peek() needs done, so use it and put it in a "static inline". Also update the documentation for rhashtable_walk_peek() to clarify the expected use case.
Signed-off-by: NeilBrown <neilb@suse.com> ---
v2 as static-inline - suggested by Tom.
Thanks, NeilBrown
include/linux/rhashtable.h | 29 ++++++++++++++++++++++++++++- lib/rhashtable.c | 34 ---------------------------------- 2 files changed, 28 insertions(+), 35 deletions(-)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index d63b472e9d50..96ebc2690027 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -247,10 +247,37 @@ 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); +/** + * rhashtable_walk_peek - Return the next object to use in an interrupted walk + * @iter: Hash table iterator + * + * Returns the "current" object or NULL when the end of the table is reached. + * When an rhashtable_walk is interrupted with rhashtable_walk_stop(), + * it is often because an object was found that could not be processed + * immediately, possible because there is no more space to encode details + * of the object (e.g. when producing a seq_file from the table). + * When the walk is restarted, the same object needs to be processed again, + * if possible. The object might have been removed from the table while + * the walk was paused, so it might not be available. In that case, the + * normal "next" object should be treated as "current". + * + * To support this common case, rhashtable_walk_peek() returns the + * appropriate object to process after an interrupted walk, either the + * one that was most recently returned, or if that doesn't exist - the + * next one. + * + * Returns -EAGAIN if resize event occurred. In that case the iterator + * will rewind back to the beginning and you may continue to use it. + */ +static inline void *rhashtable_walk_peek(struct rhashtable_iter *iter) +{ + return rhashtable_walk_last_seen(iter) ?: + rhashtable_walk_next(iter); +} + void rhashtable_free_and_destroy(struct rhashtable *ht, void (*free_fn)(void *ptr, void *arg), void *arg); diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 45f2554399a5..354275037df3 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -915,40 +915,6 @@ void *rhashtable_walk_next(struct rhashtable_iter *iter) } EXPORT_SYMBOL_GPL(rhashtable_walk_next); -/** - * rhashtable_walk_peek - Return the next object but don't advance the iterator - * @iter: Hash table iterator - * - * Returns the next object or NULL when the end of the table is reached. - * - * Returns -EAGAIN if resize event occurred. Note that the iterator - * will rewind back to the beginning and you may continue to use it. - */ -void *rhashtable_walk_peek(struct rhashtable_iter *iter) -{ - struct rhlist_head *list = iter->list; - struct rhashtable *ht = iter->ht; - struct rhash_head *p = iter->p; - - if (p) - return rht_obj(ht, ht->rhlist ? &list->rhead : p); - - /* No object found in current iter, find next one in the table. */ - - if (iter->skip) { - /* A nonzero skip value points to the next entry in the table - * beyond that last one that was found. Decrement skip so - * we find the current value. __rhashtable_walk_find_next - * will restore the original value of skip assuming that - * the table hasn't changed. - */ - iter->skip--; - } - - return __rhashtable_walk_find_next(iter); -} -EXPORT_SYMBOL_GPL(rhashtable_walk_peek); - /** * rhashtable_walk_last_seen - Return the previously returned object, if available * @iter: Hash table iterator -- 2.14.0.rc0.dirty [unhandled content-type:application/pgp-signature]
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