From patchwork Sat Jan 15 05:30:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shin'ichiro Kawasaki X-Patchwork-Id: 12714333 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93AD3C433F5 for ; Sat, 15 Jan 2022 05:30:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231546AbiAOFaO (ORCPT ); Sat, 15 Jan 2022 00:30:14 -0500 Received: from esa5.hgst.iphmx.com ([216.71.153.144]:21058 "EHLO esa5.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231184AbiAOFaO (ORCPT ); Sat, 15 Jan 2022 00:30:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=wdc.com; i=@wdc.com; q=dns/txt; s=dkim.wdc.com; t=1642224612; x=1673760612; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=YEHBeI/E5YkcD9KAl1Jh//gqXq3LV/3CA4dNroqZewc=; b=o1TfTFjLypeUOkVGj6GmHO0wG+nMSZFKwU8sGpWCN2EhYTYJHa1VuUbk tQq5OjZI+le5UN+tOizKndJ2uzSMC6vWCPhKY4F7B36rKw978GoSLwS7C DjVzhP6EIvtcxC05twpcu0RzJ4ugwSVJKiPXVObtEIczIbAUX13asBH90 FU3U/9ZkLreB3oVxO+/F+eRpr6p8mVX6kTp23yMMedPlkk3ZS+JhvpdhD IVq3gCT3NFNaQftxOdJpkiLMdtQN/LAY66cns4PXvjXtTeQcT4z5c4Gv3 pimTV5zEbTTHb7cbaweLsspAFlqJgUdkBnhTGCJ5ORIs1RSX6B1ZzC64K Q==; X-IronPort-AV: E=Sophos;i="5.88,290,1635177600"; d="scan'208";a="190519211" Received: from h199-255-45-14.hgst.com (HELO uls-op-cesaep01.wdc.com) ([199.255.45.14]) by ob1.hgst.iphmx.com with ESMTP; 15 Jan 2022 13:30:11 +0800 IronPort-SDR: 59K07VHmLNY/4kN2VMdI1t4awANCLrPa0orkzQO6Qt1M2Y1yW/f1l4h5cfZstqGFVbyhoa8z6k bnti2mguuJyXXu6q+Ew9oB6rMTp9lmYHOdBIUV8175qOK1fvWfjgFOBvwjBpVJZd8ghxLkrKAV pcjugCzTb/aSS9S+DR8n7I0XcheBbCBAeakxKrNmUgPwPs3MP+LjZsEECMh1NghQi6BBTuV1ps 6Zgnms85j/ETFDcLucaITDkwhRRpN552RTNKeFKfG326zrDN0+zvPTArzp8dg/WyixUMhUjdOy CgtBlU0dlLiRGO0lOJ8So5LJ Received: from uls-op-cesaip01.wdc.com ([10.248.3.36]) by uls-op-cesaep01.wdc.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2022 21:03:50 -0800 IronPort-SDR: UjZQs0qce89f+YhX9UtXBlgRXMGpsy8ieDN1QdtutjPoRKmOIay+qKLyiygpnEpnOJJLfjqJoq FD73elAGlYzZHU1/4ZpjKelXjPy79eysqKEo2jjC+SK3/0ODIq0wpppQzenV4L1xZ2UvdUwiGs JT1OIP43k6OiLVWFVB8hGYwOy0sfEaYi3i+f6Mj3uGwpWjBcIpYUI340ND685RtkG897TbsRaa qQuf47Vei55uD78Q3yzeDBPlEHFdbeDTTmUuOq8v1mfVbvuq9cmx6fet8GPWoDEexhzDHjldjS uCs= WDCIronportException: Internal Received: from shindev.dhcp.fujisawa.hgst.com (HELO shindev.fujisawa.hgst.com) ([10.149.52.173]) by uls-op-cesaip01.wdc.com with ESMTP; 14 Jan 2022 21:30:13 -0800 From: Shin'ichiro Kawasaki To: linux-btrfs@vger.kernel.org, David Sterba Cc: Naohiro Aota , Johannes Thumshirn , Damien Le Moal , Shin'ichiro Kawasaki Subject: [PATCH v2] btrfs: fix deadlock between quota disable and qgroup rescan worker Date: Sat, 15 Jan 2022 14:30:12 +0900 Message-Id: <20220115053012.941761-1-shinichiro.kawasaki@wdc.com> X-Mailer: git-send-email 2.33.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Quota disable ioctl starts a transaction before waiting for the qgroup rescan worker completes. However, this wait can be infinite and results in deadlock because of circular dependency among the quota disable ioctl, the qgroup rescan worker and the other task with transaction such as block group relocation task. The deadlock happens with the steps following: 1) Task A calls ioctl to disable quota. It starts a transaction and waits for qgroup rescan worker completes. 2) Task B such as block group relocation task starts a transaction and joins to the transaction that task A started. Then task B commits to the transaction. In this commit, task B waits for a commit by task A. 3) Task C as the qgroup rescan worker starts its job and starts a transaction. In this transaction start, task C waits for completion of the transaction that task A started and task B committed. This deadlock was found with fstests test case block/115 and a zoned null_blk device. The test case enables and disables quota, and the block group reclaim was triggered during the quota disable by chance. The deadlock was also observed by running quota enable and disable in parallel with 'btrfs balance' command on regular null_blk devices. An example report of the deadlock: [ 372.469894] INFO: task kworker/u16:6:103 blocked for more than 122 seconds. [ 372.479944] Not tainted 5.16.0-rc8 #7 [ 372.485067] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 372.493898] task:kworker/u16:6 state:D stack: 0 pid: 103 ppid: 2 flags:0x00004000 [ 372.503285] Workqueue: btrfs-qgroup-rescan btrfs_work_helper [btrfs] [ 372.510782] Call Trace: [ 372.514092] [ 372.521684] __schedule+0xb56/0x4850 [ 372.530104] ? io_schedule_timeout+0x190/0x190 [ 372.538842] ? lockdep_hardirqs_on+0x7e/0x100 [ 372.547092] ? _raw_spin_unlock_irqrestore+0x3e/0x60 [ 372.555591] schedule+0xe0/0x270 [ 372.561894] btrfs_commit_transaction+0x18bb/0x2610 [btrfs] [ 372.570506] ? btrfs_apply_pending_changes+0x50/0x50 [btrfs] [ 372.578875] ? free_unref_page+0x3f2/0x650 [ 372.585484] ? finish_wait+0x270/0x270 [ 372.591594] ? release_extent_buffer+0x224/0x420 [btrfs] [ 372.599264] btrfs_qgroup_rescan_worker+0xc13/0x10c0 [btrfs] [ 372.607157] ? lock_release+0x3a9/0x6d0 [ 372.613054] ? btrfs_qgroup_account_extent+0xda0/0xda0 [btrfs] [ 372.620960] ? do_raw_spin_lock+0x11e/0x250 [ 372.627137] ? rwlock_bug.part.0+0x90/0x90 [ 372.633215] ? lock_is_held_type+0xe4/0x140 [ 372.639404] btrfs_work_helper+0x1ae/0xa90 [btrfs] [ 372.646268] process_one_work+0x7e9/0x1320 [ 372.652321] ? lock_release+0x6d0/0x6d0 [ 372.658081] ? pwq_dec_nr_in_flight+0x230/0x230 [ 372.664513] ? rwlock_bug.part.0+0x90/0x90 [ 372.670529] worker_thread+0x59e/0xf90 [ 372.676172] ? process_one_work+0x1320/0x1320 [ 372.682440] kthread+0x3b9/0x490 [ 372.687550] ? _raw_spin_unlock_irq+0x24/0x50 [ 372.693811] ? set_kthread_struct+0x100/0x100 [ 372.700052] ret_from_fork+0x22/0x30 [ 372.705517] [ 372.709747] INFO: task btrfs-transacti:2347 blocked for more than 123 seconds. [ 372.729827] Not tainted 5.16.0-rc8 #7 [ 372.745907] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 372.767106] task:btrfs-transacti state:D stack: 0 pid: 2347 ppid: 2 flags:0x00004000 [ 372.787776] Call Trace: [ 372.801652] [ 372.812961] __schedule+0xb56/0x4850 [ 372.830011] ? io_schedule_timeout+0x190/0x190 [ 372.852547] ? lockdep_hardirqs_on+0x7e/0x100 [ 372.871761] ? _raw_spin_unlock_irqrestore+0x3e/0x60 [ 372.886792] schedule+0xe0/0x270 [ 372.901685] wait_current_trans+0x22c/0x310 [btrfs] [ 372.919743] ? btrfs_put_transaction+0x3d0/0x3d0 [btrfs] [ 372.938923] ? finish_wait+0x270/0x270 [ 372.959085] ? join_transaction+0xc75/0xe30 [btrfs] [ 372.977706] start_transaction+0x938/0x10a0 [btrfs] [ 372.997168] transaction_kthread+0x19d/0x3c0 [btrfs] [ 373.013021] ? btrfs_cleanup_transaction.isra.0+0xfc0/0xfc0 [btrfs] [ 373.031678] kthread+0x3b9/0x490 [ 373.047420] ? _raw_spin_unlock_irq+0x24/0x50 [ 373.064645] ? set_kthread_struct+0x100/0x100 [ 373.078571] ret_from_fork+0x22/0x30 [ 373.091197] [ 373.105611] INFO: task btrfs:3145 blocked for more than 123 seconds. [ 373.114147] Not tainted 5.16.0-rc8 #7 [ 373.120401] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 373.130393] task:btrfs state:D stack: 0 pid: 3145 ppid: 3141 flags:0x00004000 [ 373.140998] Call Trace: [ 373.145501] [ 373.149654] __schedule+0xb56/0x4850 [ 373.155306] ? io_schedule_timeout+0x190/0x190 [ 373.161965] ? lockdep_hardirqs_on+0x7e/0x100 [ 373.168469] ? _raw_spin_unlock_irqrestore+0x3e/0x60 [ 373.175468] schedule+0xe0/0x270 [ 373.180814] wait_for_commit+0x104/0x150 [btrfs] [ 373.187643] ? test_and_set_bit+0x20/0x20 [btrfs] [ 373.194772] ? kmem_cache_free+0x124/0x550 [ 373.201191] ? btrfs_put_transaction+0x69/0x3d0 [btrfs] [ 373.208738] ? finish_wait+0x270/0x270 [ 373.214704] ? __btrfs_end_transaction+0x347/0x7b0 [btrfs] [ 373.222342] btrfs_commit_transaction+0x44d/0x2610 [btrfs] [ 373.230233] ? join_transaction+0x255/0xe30 [btrfs] [ 373.237334] ? btrfs_record_root_in_trans+0x4d/0x170 [btrfs] [ 373.245251] ? btrfs_apply_pending_changes+0x50/0x50 [btrfs] [ 373.253296] relocate_block_group+0x105/0xc20 [btrfs] [ 373.260533] ? mutex_lock_io_nested+0x1270/0x1270 [ 373.267516] ? btrfs_wait_nocow_writers+0x85/0x180 [btrfs] [ 373.275155] ? merge_reloc_roots+0x710/0x710 [btrfs] [ 373.283602] ? btrfs_wait_ordered_extents+0xd30/0xd30 [btrfs] [ 373.291934] ? kmem_cache_free+0x124/0x550 [ 373.298180] btrfs_relocate_block_group+0x35c/0x930 [btrfs] [ 373.306047] btrfs_relocate_chunk+0x85/0x210 [btrfs] [ 373.313229] btrfs_balance+0x12f4/0x2d20 [btrfs] [ 373.320227] ? lock_release+0x3a9/0x6d0 [ 373.326206] ? btrfs_relocate_chunk+0x210/0x210 [btrfs] [ 373.333591] ? lock_is_held_type+0xe4/0x140 [ 373.340031] ? rcu_read_lock_sched_held+0x3f/0x70 [ 373.346910] btrfs_ioctl_balance+0x548/0x700 [btrfs] [ 373.354207] btrfs_ioctl+0x7f2/0x71b0 [btrfs] [ 373.360774] ? lockdep_hardirqs_on_prepare+0x410/0x410 [ 373.367957] ? lockdep_hardirqs_on_prepare+0x410/0x410 [ 373.375327] ? btrfs_ioctl_get_supported_features+0x20/0x20 [btrfs] [ 373.383841] ? find_held_lock+0x2c/0x110 [ 373.389993] ? lock_release+0x3a9/0x6d0 [ 373.395828] ? mntput_no_expire+0xf7/0xad0 [ 373.402083] ? lock_is_held_type+0xe4/0x140 [ 373.408249] ? vfs_fileattr_set+0x9f0/0x9f0 [ 373.414486] ? selinux_file_ioctl+0x349/0x4e0 [ 373.420938] ? trace_raw_output_lock+0xb4/0xe0 [ 373.427442] ? selinux_inode_getsecctx+0x80/0x80 [ 373.434224] ? lockdep_hardirqs_on+0x7e/0x100 [ 373.440660] ? force_qs_rnp+0x2a0/0x6b0 [ 373.446534] ? lock_is_held_type+0x9b/0x140 [ 373.452763] ? __blkcg_punt_bio_submit+0x1b0/0x1b0 [ 373.459732] ? security_file_ioctl+0x50/0x90 [ 373.466089] __x64_sys_ioctl+0x127/0x190 [ 373.472022] do_syscall_64+0x3b/0x90 [ 373.477513] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 373.484823] RIP: 0033:0x7f8f4af7e2bb [ 373.490493] RSP: 002b:00007ffcbf936178 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 373.500197] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8f4af7e2bb [ 373.509451] RDX: 00007ffcbf936220 RSI: 00000000c4009420 RDI: 0000000000000003 [ 373.518659] RBP: 00007ffcbf93774a R08: 0000000000000013 R09: 00007f8f4b02d4e0 [ 373.527872] R10: 00007f8f4ae87740 R11: 0000000000000246 R12: 0000000000000001 [ 373.537222] R13: 00007ffcbf936220 R14: 0000000000000000 R15: 0000000000000002 [ 373.546506] [ 373.550878] INFO: task btrfs:3146 blocked for more than 123 seconds. [ 373.559383] Not tainted 5.16.0-rc8 #7 [ 373.565748] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 373.575748] task:btrfs state:D stack: 0 pid: 3146 ppid: 2168 flags:0x00000000 [ 373.586314] Call Trace: [ 373.590846] [ 373.595121] __schedule+0xb56/0x4850 [ 373.600901] ? __lock_acquire+0x23db/0x5030 [ 373.607176] ? io_schedule_timeout+0x190/0x190 [ 373.613954] schedule+0xe0/0x270 [ 373.619157] schedule_timeout+0x168/0x220 [ 373.625170] ? usleep_range_state+0x150/0x150 [ 373.631653] ? mark_held_locks+0x9e/0xe0 [ 373.637767] ? do_raw_spin_lock+0x11e/0x250 [ 373.643993] ? lockdep_hardirqs_on_prepare+0x17b/0x410 [ 373.651267] ? _raw_spin_unlock_irq+0x24/0x50 [ 373.657677] ? lockdep_hardirqs_on+0x7e/0x100 [ 373.664103] wait_for_completion+0x163/0x250 [ 373.670437] ? bit_wait_timeout+0x160/0x160 [ 373.676585] btrfs_quota_disable+0x176/0x9a0 [btrfs] [ 373.683979] ? btrfs_quota_enable+0x12f0/0x12f0 [btrfs] [ 373.691340] ? down_write+0xd0/0x130 [ 373.696880] ? down_write_killable+0x150/0x150 [ 373.703352] btrfs_ioctl+0x3945/0x71b0 [btrfs] [ 373.710061] ? find_held_lock+0x2c/0x110 [ 373.716192] ? lock_release+0x3a9/0x6d0 [ 373.722047] ? __handle_mm_fault+0x23cd/0x3050 [ 373.728486] ? btrfs_ioctl_get_supported_features+0x20/0x20 [btrfs] [ 373.737032] ? set_pte+0x6a/0x90 [ 373.742271] ? do_raw_spin_unlock+0x55/0x1f0 [ 373.748506] ? lock_is_held_type+0xe4/0x140 [ 373.754792] ? vfs_fileattr_set+0x9f0/0x9f0 [ 373.761083] ? selinux_file_ioctl+0x349/0x4e0 [ 373.767521] ? selinux_inode_getsecctx+0x80/0x80 [ 373.774247] ? __up_read+0x182/0x6e0 [ 373.780026] ? count_memcg_events.constprop.0+0x46/0x60 [ 373.787281] ? up_write+0x460/0x460 [ 373.792932] ? security_file_ioctl+0x50/0x90 [ 373.799232] __x64_sys_ioctl+0x127/0x190 [ 373.805237] do_syscall_64+0x3b/0x90 [ 373.810947] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 373.818102] RIP: 0033:0x7f1383ea02bb [ 373.823847] RSP: 002b:00007fffeb4d71f8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 [ 373.833641] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1383ea02bb [ 373.842961] RDX: 00007fffeb4d7210 RSI: 00000000c0109428 RDI: 0000000000000003 [ 373.852179] RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000078 [ 373.861408] R10: 00007f1383daec78 R11: 0000000000000202 R12: 00007fffeb4d874a [ 373.870647] R13: 0000000000493099 R14: 0000000000000001 R15: 0000000000000000 [ 373.879838] [ 373.884018] Showing all locks held in the system: [ 373.894250] 3 locks held by kworker/4:1/58: [ 373.900356] 1 lock held by khungtaskd/63: [ 373.906333] #0: ffffffff8945ff60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 [ 373.917307] 3 locks held by kworker/u16:6/103: [ 373.923938] #0: ffff888127b4f138 ((wq_completion)btrfs-qgroup-rescan){+.+.}-{0:0}, at: process_one_work+0x712/0x1320 [ 373.936555] #1: ffff88810b817dd8 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_one_work+0x73f/0x1320 [ 373.951109] #2: ffff888102dd4650 (sb_internal#2){.+.+}-{0:0}, at: btrfs_qgroup_rescan_worker+0x1f6/0x10c0 [btrfs] [ 373.964027] 2 locks held by less/1803: [ 373.969982] #0: ffff88813ed56098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 [ 373.981295] #1: ffffc90000b3b2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x9e2/0x1060 [ 373.992969] 1 lock held by btrfs-transacti/2347: [ 373.999893] #0: ffff88813d4887a8 (&fs_info->transaction_kthread_mutex){+.+.}-{3:3}, at: transaction_kthread+0xe3/0x3c0 [btrfs] [ 374.015872] 3 locks held by btrfs/3145: [ 374.022298] #0: ffff888102dd4460 (sb_writers#18){.+.+}-{0:0}, at: btrfs_ioctl_balance+0xc3/0x700 [btrfs] [ 374.034456] #1: ffff88813d48a0a0 (&fs_info->reclaim_bgs_lock){+.+.}-{3:3}, at: btrfs_balance+0xfe5/0x2d20 [btrfs] [ 374.047646] #2: ffff88813d488838 (&fs_info->cleaner_mutex){+.+.}-{3:3}, at: btrfs_relocate_block_group+0x354/0x930 [btrfs] [ 374.063295] 4 locks held by btrfs/3146: [ 374.069647] #0: ffff888102dd4460 (sb_writers#18){.+.+}-{0:0}, at: btrfs_ioctl+0x38b1/0x71b0 [btrfs] [ 374.081601] #1: ffff88813d488bb8 (&fs_info->subvol_sem){+.+.}-{3:3}, at: btrfs_ioctl+0x38fd/0x71b0 [btrfs] [ 374.094283] #2: ffff888102dd4650 (sb_internal#2){.+.+}-{0:0}, at: btrfs_quota_disable+0xc8/0x9a0 [btrfs] [ 374.106885] #3: ffff88813d489800 (&fs_info->qgroup_ioctl_lock){+.+.}-{3:3}, at: btrfs_quota_disable+0xd5/0x9a0 [btrfs] [ 374.126780] ============================================= To avoid the deadlock, wait for the qgroup rescan worker to complete before starting the transaction for the quota disable ioctl. Clear BTRFS_FS_QUOTA_ENABLE flag before the wait and the transaction to request the worker to complete. Check that the flag is not cleared at the beginning of quota disable ioctl. This avoids reentrance to the function btrfs_quota_disable and allows to set BTRFS_FS_QUOTA_ENABLE flag again safely on transaction start failure, and to remove second quota_root check in the function. Also check the BTRFS_FS_QUOTA_ENABLE flag in qgroup_rescan_init to avoid another qgroup rescan worker to start after the previous qgroup worker completed. Suggested-by: Naohiro Aota Signed-off-by: Shin'ichiro Kawasaki --- Changes from v1: * Used BTRFS_FS_QUOTA_ENABLE flag instead of the new flag fs/btrfs/qgroup.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 8928275823a1..060c9014a1c7 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1188,6 +1188,16 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) mutex_lock(&fs_info->qgroup_ioctl_lock); if (!fs_info->quota_root) goto out; + + /* + * Request qgroup rescan worker to complete and wait for it. This wait + * must be done before transaction start for quota disable since it may + * deadlock with transaction by the qgroup rescan worker. + */ + if (!test_and_clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) + goto out; + + btrfs_qgroup_wait_for_completion(fs_info, false); mutex_unlock(&fs_info->qgroup_ioctl_lock); /* @@ -1205,14 +1215,10 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) if (IS_ERR(trans)) { ret = PTR_ERR(trans); trans = NULL; + set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags); goto out; } - if (!fs_info->quota_root) - goto out; - - clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags); - btrfs_qgroup_wait_for_completion(fs_info, false); spin_lock(&fs_info->qgroup_lock); quota_root = fs_info->quota_root; fs_info->quota_root = NULL; @@ -3383,6 +3389,9 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid, btrfs_warn(fs_info, "qgroup rescan init failed, qgroup is not enabled"); ret = -EINVAL; + } else if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) { + /* quota disable is in progress */ + ret = -EBUSY; } if (ret) {