From patchwork Tue Mar 4 13:05:33 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li Lingfeng X-Patchwork-Id: 14000662 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D3361EA7CE; Tue, 4 Mar 2025 12:48:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741092517; cv=none; b=BPfpfqu7ZCbQB6d6ID370rSGAnQj9xwkld1lh5/VHGNEhXlWh4cXQC2b2gspLlxKAuOGrVnB8iMUGFxhvcD32FReuSszW10LvIEI6sYzXEGDeUTvKXmdvF1RpScbaSghaPVnT//ud5/WTzapELDk+WGBE7cwYKpjVoizsL0fENE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741092517; c=relaxed/simple; bh=ODVFBe/e11v9wJrhnq4WBKSfBQBazIMfPT6QZbpiSN4=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lYCRKF5ZlzRPJu48dX+G4/e+FZ1l8Tzt2/zuwYA2Ja5ohRFoT/3hMDxn01XiIoNNPHU5tHQL2xBrMmH7uYE+EdH9rAx9EwbnZtZBBH7IHpxkt/nyHaq2EPPG+dFvWurhF32HeQY38ox/nCHW5bx5a6OT9r7N1N8ulwLfTwpzMEo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.252]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Z6b6Y4rQKzpbTS; Tue, 4 Mar 2025 20:47:01 +0800 (CST) Received: from kwepemg500017.china.huawei.com (unknown [7.202.181.81]) by mail.maildlp.com (Postfix) with ESMTPS id 7E7811800EB; Tue, 4 Mar 2025 20:48:32 +0800 (CST) Received: from huawei.com (10.175.127.227) by kwepemg500017.china.huawei.com (7.202.181.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 4 Mar 2025 20:48:31 +0800 From: Li Lingfeng To: , CC: , , , , , , , , , Subject: [PATCH 2/2] nfs: ignore SB_RDONLY when remounting nfs Date: Tue, 4 Mar 2025 21:05:33 +0800 Message-ID: <20250304130533.549840-3-lilingfeng3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20250304130533.549840-1-lilingfeng3@huawei.com> References: <20250304130533.549840-1-lilingfeng3@huawei.com> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemg500017.china.huawei.com (7.202.181.81) In some scenarios, when mounting NFS, more than one superblock may be created. The final superblock used is the last one created, but only the first superblock carries the ro flag passed from user space. If a ro flag is added to the superblock via remount, it will trigger the issue described in Link[1]. Link[2] attempted to address this by marking the superblock as ro during the initial mount. However, this introduced a new problem in scenarios where multiple mount points share the same superblock: [root@a ~]# mount /dev/sdb /mnt/sdb [root@a ~]# echo "/mnt/sdb *(rw,no_root_squash)" > /etc/exports [root@a ~]# echo "/mnt/sdb/test_dir2 *(ro,no_root_squash)" >> /etc/exports [root@a ~]# systemctl restart nfs-server [root@a ~]# mount -t nfs -o rw 127.0.0.1:/mnt/sdb/test_dir1 /mnt/test_mp1 [root@a ~]# mount | grep nfs4 127.0.0.1:/mnt/sdb/test_dir1 on /mnt/test_mp1 type nfs4 (rw,relatime,... [root@a ~]# mount -t nfs -o ro 127.0.0.1:/mnt/sdb/test_dir2 /mnt/test_mp2 [root@a ~]# mount | grep nfs4 127.0.0.1:/mnt/sdb/test_dir1 on /mnt/test_mp1 type nfs4 (ro,relatime,... 127.0.0.1:/mnt/sdb/test_dir2 on /mnt/test_mp2 type nfs4 (ro,relatime,... [root@a ~]# When mounting the second NFS, the shared superblock is marked as ro, causing the previous NFS mount to become read-only. To resolve both issues, the ro flag is no longer applied to the superblock during remount. Instead, the ro flag on the mount is used to control whether the mount point is read-only. Fixes: 281cad46b34d ("NFS: Create a submount rpc_op") Link[1]: https://lore.kernel.org/all/20240604112636.236517-3-lilingfeng@huaweicloud.com/ Link[2]: https://lore.kernel.org/all/20241130035818.1459775-1-lilingfeng3@huawei.com/ Signed-off-by: Li Lingfeng --- fs/nfs/super.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/nfs/super.c b/fs/nfs/super.c index 3e5528c2c822..8f50447eb5d0 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -1047,6 +1047,16 @@ int nfs_reconfigure(struct fs_context *fc) sync_filesystem(sb); + /* + * The SB_RDONLY flag has been removed from the superblock during + * mounts to prevent interference between different filesystems. + * Similarly, it is also necessary to ignore the SB_RDONLY flag + * during reconfiguration; otherwise, it may also result in the + * creation of redundant superblocks when mounting a directory with + * different rw and ro flags multiple times. + */ + fc->sb_flags_mask &= ~SB_RDONLY; + /* * Userspace mount programs that send binary options generally send * them populated with default values. We have no way to know which