From: Alex Xu Subject: bfq/ext4 disk IO hangs forever on resume Date: Sun, 25 Jun 2017 23:07:56 -0400 Message-ID: <20170625230756.68b4de21.alex_y_xu@yahoo.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Return-path: Received: from nm23.bullet.mail.gq1.yahoo.com ([98.136.217.6]:33442 "EHLO nm23.bullet.mail.gq1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751525AbdFZDID (ORCPT ); Sun, 25 Jun 2017 23:08:03 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi, I get hangs when resuming when using bfq-mq with ext4 on 4.12-rc6+ (currently a4fd8b3accf43d407472e34403d4b0a4df5c0e71). Steps to reproduce: 1. boot computer 2. systemctl suspend 3. wait few seconds 4. press power button 5. type "ls" into console or SSH or do anything that does disk IO Expected results: Command is executed. Actual results: Command hangs. lockdep has no comments, but sysrq-d shows that i_mutex_dir_key and jbd2_handle are held by multiple processes, leading me to suspect that ext4 is at least partially involved. [0] sysrq-w lists many blocked processes [1] This happens consistently, every time I resume the system from suspend-to-RAM using this configuration. Switching to noop IO scheduler makes it stop happening. I haven't tried switching filesystems yet. I can do more debugging (enable KASAN or whatever), but usually when I bother doing that I find someone has already sent a patch for the issue. Please CC me on replies. Cheers, Alex. [0] 4 locks held by systemd/384: #0: (sb_writers#3){.+.+.+}, at: [] mnt_want_write+0x1f/0x50 #1: (&type->i_mutex_dir_key/1){+.+.+.}, at: [] do_rmdir+0x15e/0x1e0 #2: (&type->i_mutex_dir_key){++++++}, at: [] vfs_rmdir+0x50/0x130 #3: (jbd2_handle){++++..}, at: [] start_this_handle+0xff/0x430 4 locks held by syncthing/279: #0: (&f->f_pos_lock){+.+.+.}, at: [] __fdget_pos+0x3e/0x50 #1: (sb_writers#3){.+.+.+}, at: [] vfs_write+0x17c/0x1d0 #2: (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [] ext4_file_write_iter+0x57/0x350 #3: (jbd2_handle){++++..}, at: [] start_this_handle+0xff/0x430 2 locks held by zsh/238: #0: (&tty->ldisc_sem){++++.+}, at: [] ldsem_down_read+0x1f/0x30 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0xb0/0x8b0 2 locks held by sddm-greeter/267: #0: (sb_writers#3){.+.+.+}, at: [] mnt_want_write+0x1f/0x50 #1: (&type->i_mutex_dir_key){++++++}, at: [] path_openat+0x2d8/0xa10 2 locks held by kworker/u16:28/330: #0: ("events_unbound"){.+.+.+}, at: [] process_one_work+0x1c3/0x420 #1: ((&entry->work)){+.+.+.}, at: [] process_one_work+0x1c3/0x420 1 lock held by zsh/382: #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x30/0x70 [1] task PC stack pid father systemd D 0 384 0 0x00000000 Call Trace: __schedule+0x295/0x7c0 ? bit_wait+0x50/0x50 ? bit_wait+0x50/0x50 schedule+0x31/0x80 io_schedule+0x11/0x40 bit_wait_io+0xc/0x50 __wait_on_bit+0x53/0x80 ? bit_wait+0x50/0x50 out_of_line_wait_on_bit+0x6e/0x80 ? autoremove_wake_function+0x30/0x30 do_get_write_access+0x20b/0x420 jbd2_journal_get_write_access+0x2c/0x60 __ext4_journal_get_write_access+0x55/0xa0 ext4_delete_entry+0x8c/0x140 ? __ext4_journal_start_sb+0x4e/0xa0 ext4_rmdir+0x114/0x250 vfs_rmdir+0x6e/0x130 do_rmdir+0x1a3/0x1e0 SyS_unlinkat+0x1d/0x30 entry_SYSCALL_64_fastpath+0x18/0xad jbd2/sda1-8 D 0 81 2 0x00000000 Call Trace: __schedule+0x295/0x7c0 ? bit_wait+0x50/0x50 schedule+0x31/0x80 io_schedule+0x11/0x40 bit_wait_io+0xc/0x50 __wait_on_bit+0x53/0x80 ? bit_wait+0x50/0x50 out_of_line_wait_on_bit+0x6e/0x80 ? autoremove_wake_function+0x30/0x30 __wait_on_buffer+0x2d/0x30 jbd2_journal_commit_transaction+0xe6a/0x1700 kjournald2+0xc8/0x270 ? kjournald2+0xc8/0x270 ? wake_atomic_t_function+0x50/0x50 kthread+0xfe/0x130 ? commit_timeout+0x10/0x10 ? kthread_create_on_node+0x40/0x40 ret_from_fork+0x27/0x40 [ more processes follow, some different tracebacks ]