Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964864Ab3CZPVz (ORCPT ); Tue, 26 Mar 2013 11:21:55 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:53552 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934757Ab3CZPVt (ORCPT ); Tue, 26 Mar 2013 11:21:49 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Eric Sandeen , Josef Bacik , Chris Mason , Luis Henriques Subject: [PATCH 019/150] btrfs: use rcu_barrier() to wait for bdev puts at unmount Date: Tue, 26 Mar 2013 15:18:38 +0000 Message-Id: <1364311249-14454-20-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1364311249-14454-1-git-send-email-luis.henriques@canonical.com> References: <1364311249-14454-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1977 Lines: 65 3.5.7.9 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Sandeen commit bc178622d40d87e75abc131007342429c9b03351 upstream. Doing this would reliably fail with -EBUSY for me: ... unable to open /dev/sdb2: Device or resource busy because mkfs.btrfs tries to open the device O_EXCL, and somebody still has it. Using systemtap to track bdev gets & puts shows a kworker thread doing a blkdev put after mkfs attempts a get; this is left over from the unmount path: btrfs_close_devices __btrfs_close_devices call_rcu(&device->rcu, free_device); free_device INIT_WORK(&device->rcu_work, __free_device); schedule_work(&device->rcu_work); so unmount might complete before __free_device fires & does its blkdev_put. Adding an rcu_barrier() to btrfs_close_devices() causes unmount to wait until all blkdev_put()s are done, and the device is truly free once unmount completes. Signed-off-by: Eric Sandeen Signed-off-by: Josef Bacik Signed-off-by: Chris Mason Signed-off-by: Luis Henriques --- fs/btrfs/volumes.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 2208f0f..446896d 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -609,6 +609,12 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices) __btrfs_close_devices(fs_devices); free_fs_devices(fs_devices); } + /* + * Wait for rcu kworkers under __btrfs_close_devices + * to finish all blkdev_puts so device is really + * free when umount is done. + */ + rcu_barrier(); return ret; } -- 1.8.1.2 -- 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/