Message-ID: <CAKFNMomm3CwGT5SJaVwTwDYj3n34+ZyPsKnvpWgFAgoXLQRMEw@mail.gmail.com>
Date: Tue, 30 Jan 2024 02:31:25 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: syzbot <syzbot+ee2ae68da3b22d04cd8d@...kaller.appspotmail.com>
Cc: adilger.kernel@...ger.ca, akpm@...ux-foundation.org, 
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-nilfs@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, tytso@....edu, willy@...radead.org
Subject: Re: [syzbot] [ext4?] [nilfs?] INFO: task hung in migrate_pages_batch

On Mon, Jan 29, 2024 at 2:15 AM syzbot
<syzbot+ee2ae68da3b22d04cd8d@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    0802e17d9aca Merge branch 'for-next/core' into for-kernelci
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=10832107e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f9616b7e180577ba
> dashboard link: https://syzkaller.appspot.com/bug?extid=ee2ae68da3b22d04cd8d
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=163043bfe80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1306c1e3e80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/e84e45f27a78/disk-0802e17d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a8b16d2fc3b1/vmlinux-0802e17d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4c7ac36b3de1/Image-0802e17d.gz.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/e31cee0eb927/mount_10.gz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ee2ae68da3b22d04cd8d@...kaller.appspotmail.com
>
> INFO: task syz-executor439:7446 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7446  tgid:7429  ppid:6155   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  io_schedule+0x8c/0x12c kernel/sched/core.c:8998
>  folio_wait_bit_common+0x65c/0xb90 mm/filemap.c:1273
>  folio_wait_bit+0x30/0x40 mm/filemap.c:1412
>  folio_wait_writeback+0x14c/0x3bc mm/page-writeback.c:3065
>  migrate_folio_unmap mm/migrate.c:1191 [inline]
>  migrate_pages_batch+0xc1c/0x25b0 mm/migrate.c:1680
>  migrate_pages_sync mm/migrate.c:1873 [inline]
>  migrate_pages+0x1bf8/0x3114 mm/migrate.c:1955
>  do_mbind mm/mempolicy.c:1344 [inline]
>  kernel_mbind mm/mempolicy.c:1486 [inline]
>  __do_sys_mbind mm/mempolicy.c:1560 [inline]
>  __se_sys_mbind mm/mempolicy.c:1556 [inline]
>  __arm64_sys_mbind+0x1410/0x18e8 mm/mempolicy.c:1556
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> INFO: task segctord:7440 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:segctord        state:D stack:0     pid:7440  tgid:7440  ppid:2      flags:0x00000008
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  io_schedule+0x8c/0x12c kernel/sched/core.c:8998
>  folio_wait_bit_common+0x65c/0xb90 mm/filemap.c:1273
>  __folio_lock+0x2c/0x3c mm/filemap.c:1611
>  folio_lock include/linux/pagemap.h:1031 [inline]
>  nilfs_lookup_dirty_data_buffers+0x2b0/0x7e8 fs/nilfs2/segment.c:727
>  nilfs_segctor_scan_file+0x1e4/0xcdc fs/nilfs2/segment.c:1084
>  nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1206 [inline]
>  nilfs_segctor_collect fs/nilfs2/segment.c:1533 [inline]
>  nilfs_segctor_do_construct+0x16ec/0x6560 fs/nilfs2/segment.c:2081
>  nilfs_segctor_construct+0x110/0x768 fs/nilfs2/segment.c:2415
>  nilfs_segctor_thread_construct fs/nilfs2/segment.c:2523 [inline]
>  nilfs_segctor_thread+0x3d4/0xd74 fs/nilfs2/segment.c:2606
>  kthread+0x288/0x310 kernel/kthread.c:388
>  ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857
> INFO: task syz-executor439:7442 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7442  tgid:7441  ppid:6156   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  wb_wait_for_completion+0x154/0x29c fs/fs-writeback.c:192
>  sync_inodes_sb+0x220/0x944 fs/fs-writeback.c:2758
>  sync_inodes_one_sb+0x58/0x70 fs/sync.c:77
>  iterate_supers+0xd4/0x188 fs/super.c:971
>  ksys_sync+0xb4/0x1cc fs/sync.c:102
>  __arm64_sys_sync+0x14/0x24 fs/sync.c:113
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> INFO: task syz-executor439:7445 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7445  tgid:7444  ppid:6160   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6835
>  rwsem_down_write_slowpath+0xcfc/0x1aa0 kernel/locking/rwsem.c:1178
>  __down_write_common kernel/locking/rwsem.c:1306 [inline]
>  __down_write kernel/locking/rwsem.c:1315 [inline]
>  down_write+0xb4/0xc0 kernel/locking/rwsem.c:1580
>  bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
>  sync_inodes_one_sb+0x58/0x70 fs/sync.c:77
>  iterate_supers+0xd4/0x188 fs/super.c:971
>  ksys_sync+0xb4/0x1cc fs/sync.c:102
>  __arm64_sys_sync+0x14/0x24 fs/sync.c:113
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> INFO: task syz-executor439:7450 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7450  tgid:7448  ppid:6153   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6835
>  rwsem_down_write_slowpath+0xcfc/0x1aa0 kernel/locking/rwsem.c:1178
>  __down_write_common kernel/locking/rwsem.c:1306 [inline]
>  __down_write kernel/locking/rwsem.c:1315 [inline]
>  down_write+0xb4/0xc0 kernel/locking/rwsem.c:1580
>  bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
>  sync_inodes_one_sb+0x58/0x70 fs/sync.c:77
>  iterate_supers+0xd4/0x188 fs/super.c:971
>  ksys_sync+0xb4/0x1cc fs/sync.c:102
>  __arm64_sys_sync+0x14/0x24 fs/sync.c:113
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> INFO: task syz-executor439:7451 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7451  tgid:7449  ppid:6154   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6835
>  rwsem_down_write_slowpath+0xcfc/0x1aa0 kernel/locking/rwsem.c:1178
>  __down_write_common kernel/locking/rwsem.c:1306 [inline]
>  __down_write kernel/locking/rwsem.c:1315 [inline]
>  down_write+0xb4/0xc0 kernel/locking/rwsem.c:1580
>  bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
>  sync_inodes_one_sb+0x58/0x70 fs/sync.c:77
>  iterate_supers+0xd4/0x188 fs/super.c:971
>  ksys_sync+0xb4/0x1cc fs/sync.c:102
>  __arm64_sys_sync+0x14/0x24 fs/sync.c:113
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
> INFO: task syz-executor439:7460 blocked for more than 143 seconds.
>       Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor439 state:D stack:0     pid:7460  tgid:7456  ppid:6161   flags:0x0000000d
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5376 [inline]
>  __schedule+0x1354/0x2360 kernel/sched/core.c:6688
>  __schedule_loop kernel/sched/core.c:6763 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6778
>  schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6835
>  rwsem_down_write_slowpath+0xcfc/0x1aa0 kernel/locking/rwsem.c:1178
>  __down_write_common kernel/locking/rwsem.c:1306 [inline]
>  __down_write kernel/locking/rwsem.c:1315 [inline]
>  down_write+0xb4/0xc0 kernel/locking/rwsem.c:1580
>  bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
>  sync_inodes_one_sb+0x58/0x70 fs/sync.c:77
>  iterate_supers+0xd4/0x188 fs/super.c:971
>  ksys_sync+0xb4/0x1cc fs/sync.c:102
>  __arm64_sys_sync+0x14/0x24 fs/sync.c:113
>  __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
>  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
>  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
>  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
>  el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
>  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
>  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
>
> Showing all locks held in the system:
> 1 lock held by khungtaskd/29:
>  #0: ffff80008e6c48c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:300
> 2 locks held by kworker/u4:3/41:
>  #0: ffff0000c1c3a138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work+0x560/0x1204 kernel/workqueue.c:2600
>  #1: ffff8000943f7c20 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x5a0/0x1204 kernel/workqueue.c:2602
> 2 locks held by getty/5863:
>  #0: ffff0000d255f0a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
>  #1: ffff800094e702f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41c/0x1228 drivers/tty/n_tty.c:2201
> 1 lock held by segctord/7440:
>  #0: ffff0000c7ade2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x178/0x33c fs/nilfs2/segment.c:357
> 2 locks held by syz-executor439/7442:
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
> 2 locks held by syz-executor439/7445:
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
> 2 locks held by syz-executor439/7450:
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
> 2 locks held by syz-executor439/7451:
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
> 2 locks held by syz-executor439/7460:
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
>  #0: ffff0000c5e920e0 (&type->s_umount_key#64){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:364 [inline]
>  #1: ffff0000c9d147d0 (&bdi->wb_switch_rwsem){+.+.}-{3:3}, at: sync_inodes_sb+0x208/0x944 fs/fs-writeback.c:2756
>
> =============================================
>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

The hang of this report seems to be due to an issue of nilfs2 side.  I
will fix it.

Ryusuke Konishi

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