From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B170DC6778C for ; Fri, 6 Jul 2018 07:13:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7008A219EB for ; Fri, 6 Jul 2018 07:13:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7008A219EB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754097AbeGFHNo (ORCPT ); Fri, 6 Jul 2018 03:13:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:45104 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753604AbeGFHNm (ORCPT ); Fri, 6 Jul 2018 03:13:42 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A3E8BAD80; Fri, 6 Jul 2018 07:13:40 +0000 (UTC) From: NeilBrown To: Thomas Graf , Herbert Xu , Tom Herbert Date: Fri, 06 Jul 2018 17:11:32 +1000 Subject: [PATCH 2/3] rhashtable: add rhashtable_walk_last_seen() Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <153086109260.2825.1459722786871837620.stgit@noble> In-Reply-To: <153086101070.2825.6850140624411927465.stgit@noble> References: <153086101070.2825.6850140624411927465.stgit@noble> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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