Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932855AbbFCMfg (ORCPT ); Wed, 3 Jun 2015 08:35:36 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58440 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756358AbbFCMVQ (ORCPT ); Wed, 3 Jun 2015 08:21:16 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, NeilBrown Subject: [PATCH 4.0 147/148] md: fix race when unfreezing sync_action Date: Wed, 3 Jun 2015 21:10:17 +0900 Message-Id: <20150603114211.902735563@linuxfoundation.org> X-Mailer: git-send-email 2.4.2 In-Reply-To: <20150603114205.337615117@linuxfoundation.org> References: <20150603114205.337615117@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3085 Lines: 86 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: NeilBrown commit 56ccc1125bc141cf63927eda7febff4216dea2d3 upstream. A recent change removed the need for locking around writing to "sync_action" (and various other places), but introduced a subtle race. When e.g. setting 'reshape' on a 'frozen' array, the 'frozen' flag is cleared before 'reshape' is set, so the md thread can get in and start trying recovery - which isn't wanted. So instead of clearing MD_RECOVERY_FROZEN for any command except 'frozen', only clear it when each specific command is parsed. This allows the handling of 'reshape' to clear the bit while a lock is held. Also remove some places where we set MD_RECOVERY_NEEDED, as it is always set on non-error exit of the function. Signed-off-by: NeilBrown Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.") Signed-off-by: Greg Kroah-Hartman --- drivers/md/md.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4138,12 +4138,12 @@ action_store(struct mddev *mddev, const if (!mddev->pers || !mddev->pers->sync_request) return -EINVAL; - if (cmd_match(page, "frozen")) - set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - else - clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); if (cmd_match(page, "idle") || cmd_match(page, "frozen")) { + if (cmd_match(page, "frozen")) + set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); + else + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); flush_workqueue(md_misc_wq); if (mddev->sync_thread) { set_bit(MD_RECOVERY_INTR, &mddev->recovery); @@ -4156,16 +4156,17 @@ action_store(struct mddev *mddev, const test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) return -EBUSY; else if (cmd_match(page, "resync")) - set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); else if (cmd_match(page, "recover")) { + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); set_bit(MD_RECOVERY_RECOVER, &mddev->recovery); - set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); } else if (cmd_match(page, "reshape")) { int err; if (mddev->pers->start_reshape == NULL) return -EINVAL; err = mddev_lock(mddev); if (!err) { + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); err = mddev->pers->start_reshape(mddev); mddev_unlock(mddev); } @@ -4177,6 +4178,7 @@ action_store(struct mddev *mddev, const set_bit(MD_RECOVERY_CHECK, &mddev->recovery); else if (!cmd_match(page, "repair")) return -EINVAL; + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery); set_bit(MD_RECOVERY_SYNC, &mddev->recovery); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/