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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 B18ECC43219 for ; Sat, 27 Apr 2019 15:31:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76B08206A3 for ; Sat, 27 Apr 2019 15:31:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728731AbfD0Pbf (ORCPT ); Sat, 27 Apr 2019 11:31:35 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60880 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727028AbfD0PPO (ORCPT ); Sat, 27 Apr 2019 11:15:14 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP2k-0000zK-DD; Sat, 27 Apr 2019 16:15:10 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2h-0004Pe-NP; Sat, 27 Apr 2019 16:15:07 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Dongsheng Yang" , "Ilya Dryomov" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 026/202] rbd: don't return 0 on unmap if RBD_DEV_FLAG_REMOVING is set In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ilya Dryomov commit 85f5a4d666fd9be73856ed16bb36c5af5b406b29 upstream. There is a window between when RBD_DEV_FLAG_REMOVING is set and when the device is removed from rbd_dev_list. During this window, we set "already" and return 0. Returning 0 from write(2) can confuse userspace tools because 0 indicates that nothing was written. In particular, "rbd unmap" will retry the write multiple times a second: 10:28:05.463299 write(4, "0", 1) = 0 10:28:05.463509 write(4, "0", 1) = 0 10:28:05.463720 write(4, "0", 1) = 0 10:28:05.463942 write(4, "0", 1) = 0 10:28:05.464155 write(4, "0", 1) = 0 Signed-off-by: Ilya Dryomov Tested-by: Dongsheng Yang [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/block/rbd.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -5422,7 +5422,6 @@ static ssize_t do_rbd_remove(struct bus_ struct list_head *tmp; int dev_id; unsigned long ul; - bool already = false; int ret; ret = kstrtoul(buf, 10, &ul); @@ -5447,13 +5446,13 @@ static ssize_t do_rbd_remove(struct bus_ spin_lock_irq(&rbd_dev->lock); if (rbd_dev->open_count) ret = -EBUSY; - else - already = test_and_set_bit(RBD_DEV_FLAG_REMOVING, - &rbd_dev->flags); + else if (test_and_set_bit(RBD_DEV_FLAG_REMOVING, + &rbd_dev->flags)) + ret = -EINPROGRESS; spin_unlock_irq(&rbd_dev->lock); } spin_unlock(&rbd_dev_list_lock); - if (ret < 0 || already) + if (ret) return ret; rbd_dev_header_unwatch_sync(rbd_dev);