From patchwork Wed Aug 24 05:47:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ziyang Zhang X-Patchwork-Id: 12952938 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 E60A0C00140 for ; Wed, 24 Aug 2022 05:49:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232570AbiHXFtA (ORCPT ); Wed, 24 Aug 2022 01:49:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46482 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233212AbiHXFs7 (ORCPT ); Wed, 24 Aug 2022 01:48:59 -0400 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 36856861D0; Tue, 23 Aug 2022 22:48:54 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R621e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=ziyangzhang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VN5zTYO_1661320119; Received: from localhost.localdomain(mailfrom:ZiyangZhang@linux.alibaba.com fp:SMTPD_---0VN5zTYO_1661320119) by smtp.aliyun-inc.com; Wed, 24 Aug 2022 13:48:52 +0800 From: ZiyangZhang To: ming.lei@redhat.com, axboe@kernel.dk Cc: xiaoguang.wang@linux.alibaba.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, ZiyangZhang Subject: [RFC PATCH 1/9] ublk_drv: check 'current' instead of 'ubq_daemon' Date: Wed, 24 Aug 2022 13:47:36 +0800 Message-Id: <20220824054744.77812-2-ZiyangZhang@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220824054744.77812-1-ZiyangZhang@linux.alibaba.com> References: <20220824054744.77812-1-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 updated 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;