From patchwork Tue Aug 24 14:12:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12455143 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 8901BC41537 for ; Tue, 24 Aug 2021 14:02:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E19B611CB for ; Tue, 24 Aug 2021 14:02:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237618AbhHXODC (ORCPT ); Tue, 24 Aug 2021 10:03:02 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:14317 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237558AbhHXODA (ORCPT ); Tue, 24 Aug 2021 10:03:00 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.57]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4Gv9lR5f8jz89cr; Tue, 24 Aug 2021 22:01:55 +0800 (CST) Received: from dggema762-chm.china.huawei.com (10.1.198.204) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 24 Aug 2021 22:02:09 +0800 Received: from huawei.com (10.175.127.227) by dggema762-chm.china.huawei.com (10.1.198.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 24 Aug 2021 22:02:09 +0800 From: Yu Kuai To: , , , CC: , , , , Subject: [PATCH v3 4/5] nbd: make sure request completion won't concurrent Date: Tue, 24 Aug 2021 22:12:26 +0800 Message-ID: <20210824141227.808340-5-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210824141227.808340-1-yukuai3@huawei.com> References: <20210824141227.808340-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggema762-chm.china.huawei.com (10.1.198.204) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org commit cddce0116058 ("nbd: Aovid double completion of a request") try to fix that nbd_clear_que() and recv_work() can complete a request concurrently. However, the problem still exists: t1 t2 t3 nbd_disconnect_and_put flush_workqueue recv_work blk_mq_complete_request blk_mq_complete_request_remote -> this is true WRITE_ONCE(rq->state, MQ_RQ_COMPLETE) blk_mq_raise_softirq blk_done_softirq blk_complete_reqs nbd_complete_rq blk_mq_end_request blk_mq_free_request WRITE_ONCE(rq->state, MQ_RQ_IDLE) nbd_clear_que blk_mq_tagset_busy_iter nbd_clear_req __blk_mq_free_request blk_mq_put_tag blk_mq_complete_request There are three places where request can be completed in nbd: recv_work(), nbd_clear_que() and nbd_xmit_timeout(). Since they all hold cmd->lock before completing the request, it's easy to avoid the problem by setting and checking a cmd flag. Signed-off-by: Yu Kuai --- drivers/block/nbd.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 7b9e19675224..4d5098d01758 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -416,12 +416,15 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req); struct nbd_device *nbd = cmd->nbd; struct nbd_config *config; + bool need_complete; if (!mutex_trylock(&cmd->lock)) return BLK_EH_RESET_TIMER; if (!refcount_inc_not_zero(&nbd->config_refs)) { cmd->status = BLK_STS_TIMEOUT; + need_complete = + test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); mutex_unlock(&cmd->lock); goto done; } @@ -490,11 +493,13 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req, dev_err_ratelimited(nbd_to_dev(nbd), "Connection timed out\n"); set_bit(NBD_RT_TIMEDOUT, &config->runtime_flags); cmd->status = BLK_STS_IOERR; + need_complete = test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); mutex_unlock(&cmd->lock); sock_shutdown(nbd); nbd_config_put(nbd); done: - blk_mq_complete_request(req); + if (need_complete) + blk_mq_complete_request(req); return BLK_EH_DONE; } @@ -849,6 +854,7 @@ static void recv_work(struct work_struct *work) static bool nbd_clear_req(struct request *req, void *data, bool reserved) { struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req); + bool need_complete; /* don't abort one completed request */ if (blk_mq_request_completed(req)) @@ -856,9 +862,11 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) mutex_lock(&cmd->lock); cmd->status = BLK_STS_IOERR; + need_complete = test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags); mutex_unlock(&cmd->lock); - blk_mq_complete_request(req); + if (need_complete) + blk_mq_complete_request(req); return true; }