From patchwork Wed Apr 8 05:34:00 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 6177451 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id CA8B59F1C4 for ; Wed, 8 Apr 2015 05:35:41 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id F05A1202B4 for ; Wed, 8 Apr 2015 05:35:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A3CC202A1 for ; Wed, 8 Apr 2015 05:35:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752857AbbDHFfh (ORCPT ); Wed, 8 Apr 2015 01:35:37 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:34092 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751362AbbDHFef (ORCPT ); Wed, 8 Apr 2015 01:34:35 -0400 Received: by pacyx8 with SMTP id yx8so102967998pac.1 for ; Tue, 07 Apr 2015 22:34:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:in-reply-to:references; bh=hYw557fUHAp3rnxyys/f7i8xWIxmMgGZdjZ/mBmOPZQ=; b=h/uw8hGEMNUKXRNMQHu2KenIA+4ISOyMwWBX6UYzjiccpZLZeUSl7h6bdGIM3YnHwA WRt/yTUNImYmHgaDWdsEMErFjPPEp6M6LwISDtDg9Mt1paXxGQYkdrpOO+eHOgJ3G/km 3yjoslWVSVAmFqDxy8JPTpL9XJSPl4CKjxsgyUfL9pDUdVhCvo9KsAfEgfQDVAGIhUtQ O49zP2lsxYu/Eh/qpnLGKv8bYCETIW7z1oEgQxL27oh5aJv6LvivOKv4UWWcI5E0jB7+ JU4WkyplZO9olZgaUX1tRxT6FefvBdbB5+hzo3jMnPIFFbnybc98aZ7Y6dOZEQNXCu05 FRBw== X-Gm-Message-State: ALoCoQme2N3SUuQjJikXh71WNfNroOqjOmGFdxPn9MUfhgd6qCRszPR9coLZCOU6T+mQznMR9h2v X-Received: by 10.66.157.106 with SMTP id wl10mr42251353pab.57.1428471274444; Tue, 07 Apr 2015 22:34:34 -0700 (PDT) Received: from mew.localdomain (c-76-104-211-44.hsd1.wa.comcast.net. [76.104.211.44]) by mx.google.com with ESMTPSA id r4sm9898338pdg.11.2015.04.07.22.34.33 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 07 Apr 2015 22:34:33 -0700 (PDT) From: Omar Sandoval To: Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Omar Sandoval Subject: [PATCH 1/3] Btrfs: lock superblock before remounting for rw subvol Date: Tue, 7 Apr 2015 22:34:00 -0700 Message-Id: X-Mailer: git-send-email 2.3.5 In-Reply-To: References: In-Reply-To: References: Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Since commit 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with different ro/rw options"), when mounting a subvolume read/write when another subvolume has previously been mounted read-only, we first do a remount. However, this should be done with the superblock locked, as per sync_filesystem(): /* * We need to be protected against the filesystem going from * r/o to r/w or vice versa. */ WARN_ON(!rwsem_is_locked(&sb->s_umount)); This WARN_ON can easily be hit with: mkfs.btrfs -f /dev/vdb mount /dev/vdb /mnt btrfs subvol create /mnt/vol1 btrfs subvol create /mnt/vol2 umount /mnt mount -oro,subvol=/vol1 /dev/vdb /mnt mount -orw,subvol=/vol2 /dev/vdb /mnt2 Fixes: 0723a0473fb4 Signed-off-by: Omar Sandoval --- fs/btrfs/super.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 05fef19..d38be09 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1205,7 +1205,9 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, return ERR_CAST(mnt); } + down_write(&mnt->mnt_sb->s_umount); r = btrfs_remount(mnt->mnt_sb, &flags, NULL); + up_write(&mnt->mnt_sb->s_umount); if (r < 0) { /* FIXME: release vfsmount mnt ??*/ kfree(newargs);