From patchwork Wed Sep 21 09:58:42 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ziyang Zhang X-Patchwork-Id: 12983573 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45CCAC32771 for ; Wed, 21 Sep 2022 09:59:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230107AbiIUJ7o (ORCPT ); Wed, 21 Sep 2022 05:59:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230229AbiIUJ7n (ORCPT ); Wed, 21 Sep 2022 05:59:43 -0400 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95B2B388E; Wed, 21 Sep 2022 02:59:40 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R631e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VQNuD7z_1663754364; Received: from localhost.localdomain(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0VQNuD7z_1663754364) by smtp.aliyun-inc.com; Wed, 21 Sep 2022 17:59:37 +0800 From: ZiyangZhang To: ming.lei@redhat.com Cc: axboe@kernel.dk, xiaoguang.wang@linux.alibaba.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, ZiyangZhang Subject: [PATCH V4 1/8] ublk_drv: check 'current' instead of 'ubq_daemon' Date: Wed, 21 Sep 2022 17:58:42 +0800 Message-Id: <20220921095849.84988-2-ZiyangZhang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220921095849.84988-1-ZiyangZhang@linux.alibaba.com> References: <20220921095849.84988-1-ZiyangZhang@linux.alibaba.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This check is not atomic. So with recovery feature, ubq_daemon may be modified simultaneously by recovery task. Instead, check 'current' is safe here because 'current' never changes. Also add comment explaining this check, which is really important for understanding recovery feature. Signed-off-by: ZiyangZhang Reviewed-by: Ming Lei --- drivers/block/ublk_drv.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 6a4a94b4cdf4..c39b67d7133d 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -645,14 +645,22 @@ static inline void __ublk_rq_task_work(struct request *req) struct ublk_device *ub = ubq->dev; int tag = req->tag; struct ublk_io *io = &ubq->ios[tag]; - bool task_exiting = current != ubq->ubq_daemon || ubq_daemon_is_dying(ubq); unsigned int mapped_bytes; pr_devel("%s: complete: op %d, qid %d tag %d io_flags %x addr %llx\n", __func__, io->cmd->cmd_op, ubq->q_id, req->tag, io->flags, ublk_get_iod(ubq, req->tag)->addr); - if (unlikely(task_exiting)) { + /* + * Task is exiting if either: + * + * (1) current != ubq_daemon. + * io_uring_cmd_complete_in_task() tries to run task_work + * in a workqueue if ubq_daemon(cmd's task) is PF_EXITING. + * + * (2) current->flags & PF_EXITING. + */ + if (unlikely(current != ubq->ubq_daemon || current->flags & PF_EXITING)) { blk_mq_end_request(req, BLK_STS_IOERR); mod_delayed_work(system_wq, &ub->monitor_work, 0); return;