From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69143C43217 for ; Mon, 13 Sep 2021 22:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C2C761264 for ; Mon, 13 Sep 2021 22:34:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348638AbhIMWgA (ORCPT ); Mon, 13 Sep 2021 18:36:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:50642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348365AbhIMWfS (ORCPT ); Mon, 13 Sep 2021 18:35:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 19A7761154; Mon, 13 Sep 2021 22:34:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631572441; bh=RFb3pID/6eYzIPR8zAD4NsiyWOu8wGB2lkNJoBScQQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y02vuGp6+U0nSpf7EdGf58Vjcp17HHdQU4q5Hg7Nd9cBywHUpbET4C7JD8zfoK3Kt 4EXbI0Gn/rT2NzvhB3v0lNYgbJ3eYQD+e1y7HY0GA5XhIn2Bi8dYqDmehgAnFBwhBt TV1FEWLMwjcIyAes4qoFnpN7WhAv/BlcIRVJlI0JAStREtC7t3DrMjVOZq24howdLQ sZLZuhZkfB2jsEjABBfSC19D6x9zXGGrPci1yeZJ4R470brgj/L+nJ1XSD1hyWJ0RJ 4M+A7zeeDNvt3kx0tmv2cQdmWwwmsRjkT0QuSvTDHcevhecbmGeszRiSv/KNTPHwiu ZgbwFTdTwb2QA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Josef Bacik , Anand Jain , David Sterba , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.14 16/25] btrfs: update the bdev time directly when closing Date: Mon, 13 Sep 2021 18:33:30 -0400 Message-Id: <20210913223339.435347-16-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210913223339.435347-1-sashal@kernel.org> References: <20210913223339.435347-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Josef Bacik [ Upstream commit 8f96a5bfa1503e0a5f3c78d51e993a1794d4aff1 ] We update the ctime/mtime of a block device when we remove it so that blkid knows the device changed. However we do this by re-opening the block device and calling filp_update_time. This is more correct because it'll call the inode->i_op->update_time if it exists, but the block dev inodes do not do this. Instead call generic_update_time() on the bd_inode in order to avoid the blkdev_open path and get rid of the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 5.14.0-rc2+ #406 Not tainted ------------------------------------------------------ losetup/11596 is trying to acquire lock: ffff939640d2f538 ((wq_completion)loop0){+.+.}-{0:0}, at: flush_workqueue+0x67/0x5e0 but task is already holding lock: ffff939655510c68 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x41/0x660 [loop] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&lo->lo_mutex){+.+.}-{3:3}: __mutex_lock+0x7d/0x750 lo_open+0x28/0x60 [loop] blkdev_get_whole+0x25/0xf0 blkdev_get_by_dev.part.0+0x168/0x3c0 blkdev_open+0xd2/0xe0 do_dentry_open+0x161/0x390 path_openat+0x3cc/0xa20 do_filp_open+0x96/0x120 do_sys_openat2+0x7b/0x130 __x64_sys_openat+0x46/0x70 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #3 (&disk->open_mutex){+.+.}-{3:3}: __mutex_lock+0x7d/0x750 blkdev_get_by_dev.part.0+0x56/0x3c0 blkdev_open+0xd2/0xe0 do_dentry_open+0x161/0x390 path_openat+0x3cc/0xa20 do_filp_open+0x96/0x120 file_open_name+0xc7/0x170 filp_open+0x2c/0x50 btrfs_scratch_superblocks.part.0+0x10f/0x170 btrfs_rm_device.cold+0xe8/0xed btrfs_ioctl+0x2a31/0x2e70 __x64_sys_ioctl+0x80/0xb0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #2 (sb_writers#12){.+.+}-{0:0}: lo_write_bvec+0xc2/0x240 [loop] loop_process_work+0x238/0xd00 [loop] process_one_work+0x26b/0x560 worker_thread+0x55/0x3c0 kthread+0x140/0x160 ret_from_fork+0x1f/0x30 -> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}: process_one_work+0x245/0x560 worker_thread+0x55/0x3c0 kthread+0x140/0x160 ret_from_fork+0x1f/0x30 -> #0 ((wq_completion)loop0){+.+.}-{0:0}: __lock_acquire+0x10ea/0x1d90 lock_acquire+0xb5/0x2b0 flush_workqueue+0x91/0x5e0 drain_workqueue+0xa0/0x110 destroy_workqueue+0x36/0x250 __loop_clr_fd+0x9a/0x660 [loop] block_ioctl+0x3f/0x50 __x64_sys_ioctl+0x80/0xb0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: (wq_completion)loop0 --> &disk->open_mutex --> &lo->lo_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&lo->lo_mutex); lock(&disk->open_mutex); lock(&lo->lo_mutex); lock((wq_completion)loop0); *** DEADLOCK *** 1 lock held by losetup/11596: #0: ffff939655510c68 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x41/0x660 [loop] stack backtrace: CPU: 1 PID: 11596 Comm: losetup Not tainted 5.14.0-rc2+ #406 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack_lvl+0x57/0x72 check_noncircular+0xcf/0xf0 ? stack_trace_save+0x3b/0x50 __lock_acquire+0x10ea/0x1d90 lock_acquire+0xb5/0x2b0 ? flush_workqueue+0x67/0x5e0 ? lockdep_init_map_type+0x47/0x220 flush_workqueue+0x91/0x5e0 ? flush_workqueue+0x67/0x5e0 ? verify_cpu+0xf0/0x100 drain_workqueue+0xa0/0x110 destroy_workqueue+0x36/0x250 __loop_clr_fd+0x9a/0x660 [loop] ? blkdev_ioctl+0x8d/0x2a0 block_ioctl+0x3f/0x50 __x64_sys_ioctl+0x80/0xb0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Reviewed-by: Anand Jain Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/volumes.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 354ffd8f81af..8dc14985128f 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1925,15 +1925,17 @@ static int btrfs_add_dev_item(struct btrfs_trans_handle *trans, * Function to update ctime/mtime for a given device path. * Mainly used for ctime/mtime based probe like libblkid. */ -static void update_dev_time(const char *path_name) +static void update_dev_time(struct block_device *bdev) { - struct file *filp; + struct inode *inode = bdev->bd_inode; + struct timespec64 now; - filp = filp_open(path_name, O_RDWR, 0); - if (IS_ERR(filp)) + /* Shouldn't happen but just in case. */ + if (!inode) return; - file_update_time(filp); - filp_close(filp, NULL); + + now = current_time(inode); + generic_update_time(inode, &now, S_MTIME | S_CTIME); } static int btrfs_rm_dev_item(struct btrfs_device *device) @@ -2113,7 +2115,7 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info, btrfs_kobject_uevent(bdev, KOBJ_CHANGE); /* Update ctime/mtime for device path for libblkid */ - update_dev_time(device_path); + update_dev_time(bdev); } int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, @@ -2766,7 +2768,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path btrfs_forget_devices(device_path); /* Update ctime/mtime for blkid or udev */ - update_dev_time(device_path); + update_dev_time(bdev); return ret; -- 2.30.2