From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: [PATCH] md: Avoid a deadlock when removing a device from an md array via sysfs. Date: Mon, 2 Apr 2007 17:44:17 +1000 Message-ID: <1070402074417.31093@suse.de> References: <20070402174319.30997.patches@notabene> Return-path: Sender: linux-raid-owner@vger.kernel.org To: Andrew Morton Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Alan Stern List-Id: linux-raid.ids (This patch should go in 2.6.21 as it fixes a recent regression - NB) A device can be removed from an md array via e.g. echo remove > /sys/block/md3/md/dev-sde/state This will try to remove the 'dev-sde' subtree which will deadlock since commit e7b0d26a86943370c04d6833c6edba2a72a6e240 With this patch we run the kobject_del via schedule_work so as to avoid the deadlock. Cc: Alan Stern Signed-off-by: Neil Brown ### Diffstat output ./drivers/md/md.c | 13 ++++++++++++- ./include/linux/raid/md_k.h | 1 + 2 files changed, 13 insertions(+), 1 deletion(-) diff .prev/drivers/md/md.c ./drivers/md/md.c --- .prev/drivers/md/md.c 2007-04-02 17:43:03.000000000 +1000 +++ ./drivers/md/md.c 2007-04-02 17:38:46.000000000 +1000 @@ -1389,6 +1389,12 @@ static int bind_rdev_to_array(mdk_rdev_t return err; } +static void delayed_delete(struct work_struct *ws) +{ + mdk_rdev_t *rdev = container_of(ws, mdk_rdev_t, del_work); + kobject_del(&rdev->kobj); +} + static void unbind_rdev_from_array(mdk_rdev_t * rdev) { char b[BDEVNAME_SIZE]; @@ -1401,7 +1407,12 @@ static void unbind_rdev_from_array(mdk_r printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b)); rdev->mddev = NULL; sysfs_remove_link(&rdev->kobj, "block"); - kobject_del(&rdev->kobj); + + /* We need to delay this, otherwise we can deadlock when + * writing to 'remove' to "dev/state" + */ + INIT_WORK(&rdev->del_work, delayed_delete); + schedule_work(&rdev->del_work); } /* diff .prev/include/linux/raid/md_k.h ./include/linux/raid/md_k.h --- .prev/include/linux/raid/md_k.h 2007-04-02 17:43:03.000000000 +1000 +++ ./include/linux/raid/md_k.h 2007-04-02 17:36:32.000000000 +1000 @@ -104,6 +104,7 @@ struct mdk_rdev_s * for reporting to userspace and storing * in superblock. */ + struct work_struct del_work; /* used for delayed sysfs removal */ }; struct mddev_s From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753391AbXDBHo1 (ORCPT ); Mon, 2 Apr 2007 03:44:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753394AbXDBHo1 (ORCPT ); Mon, 2 Apr 2007 03:44:27 -0400 Received: from mx2.suse.de ([195.135.220.15]:46551 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753391AbXDBHoZ (ORCPT ); Mon, 2 Apr 2007 03:44:25 -0400 From: NeilBrown To: Andrew Morton Date: Mon, 2 Apr 2007 17:44:17 +1000 Message-Id: <1070402074417.31093@suse.de> X-face: [Gw_3E*Gng}4rRrKRYotwlE?.2|**#s9D Subject: [PATCH] md: Avoid a deadlock when removing a device from an md array via sysfs. References: <20070402174319.30997.patches@notabene> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org (This patch should go in 2.6.21 as it fixes a recent regression - NB) A device can be removed from an md array via e.g. echo remove > /sys/block/md3/md/dev-sde/state This will try to remove the 'dev-sde' subtree which will deadlock since commit e7b0d26a86943370c04d6833c6edba2a72a6e240 With this patch we run the kobject_del via schedule_work so as to avoid the deadlock. Cc: Alan Stern Signed-off-by: Neil Brown ### Diffstat output ./drivers/md/md.c | 13 ++++++++++++- ./include/linux/raid/md_k.h | 1 + 2 files changed, 13 insertions(+), 1 deletion(-) diff .prev/drivers/md/md.c ./drivers/md/md.c --- .prev/drivers/md/md.c 2007-04-02 17:43:03.000000000 +1000 +++ ./drivers/md/md.c 2007-04-02 17:38:46.000000000 +1000 @@ -1389,6 +1389,12 @@ static int bind_rdev_to_array(mdk_rdev_t return err; } +static void delayed_delete(struct work_struct *ws) +{ + mdk_rdev_t *rdev = container_of(ws, mdk_rdev_t, del_work); + kobject_del(&rdev->kobj); +} + static void unbind_rdev_from_array(mdk_rdev_t * rdev) { char b[BDEVNAME_SIZE]; @@ -1401,7 +1407,12 @@ static void unbind_rdev_from_array(mdk_r printk(KERN_INFO "md: unbind<%s>\n", bdevname(rdev->bdev,b)); rdev->mddev = NULL; sysfs_remove_link(&rdev->kobj, "block"); - kobject_del(&rdev->kobj); + + /* We need to delay this, otherwise we can deadlock when + * writing to 'remove' to "dev/state" + */ + INIT_WORK(&rdev->del_work, delayed_delete); + schedule_work(&rdev->del_work); } /* diff .prev/include/linux/raid/md_k.h ./include/linux/raid/md_k.h --- .prev/include/linux/raid/md_k.h 2007-04-02 17:43:03.000000000 +1000 +++ ./include/linux/raid/md_k.h 2007-04-02 17:36:32.000000000 +1000 @@ -104,6 +104,7 @@ struct mdk_rdev_s * for reporting to userspace and storing * in superblock. */ + struct work_struct del_work; /* used for delayed sysfs removal */ }; struct mddev_s