syzbot


INFO: task hung in btrfs_page_mkwrite (2)

Status: upstream: reported on 2025/07/06 20:19
Reported-by: syzbot+162f21357fa4b9d1bd77@syzkaller.appspotmail.com
First crash: 52d, last: 52d
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: task hung in btrfs_page_mkwrite (3) 1 1 262d 262d 0/3 auto-obsoleted due to no activity on 2025/03/19 07:52
linux-6.1 INFO: task hung in btrfs_page_mkwrite 1 8 389d 470d 0/3 auto-obsoleted due to no activity on 2024/11/11 21:53
upstream INFO: task hung in btrfs_page_mkwrite btrfs 1 49 556d 694d 0/29 auto-obsoleted due to no activity on 2024/05/29 11:09
linux-5.15 INFO: task hung in btrfs_page_mkwrite (2) 1 4 418d 469d 0/3 auto-obsoleted due to no activity on 2024/10/14 01:09
linux-5.15 INFO: task hung in btrfs_page_mkwrite 1 1 802d 802d 0/3 auto-obsoleted due to no activity on 2023/09/26 02:15

Sample crash report:
INFO: task syz.3.173:5262 blocked for more than 143 seconds.
      Not tainted 6.1.143-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.173       state:D stack:0     pid:5262  ppid:4306   flags:0x00000009
Call trace:
 __switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
 schedule+0xc4/0x170 kernel/sched/core.c:6637
 io_schedule+0x84/0x154 kernel/sched/core.c:8797
 folio_wait_bit_common+0x56c/0x9c4 mm/filemap.c:1324
 __folio_lock+0x2c/0x3c mm/filemap.c:1687
 lock_page include/linux/pagemap.h:995 [inline]
 btrfs_page_mkwrite+0x530/0xb78 fs/btrfs/inode.c:8612
 do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
 wp_page_shared+0x148/0x550 mm/memory.c:3360
 do_wp_page+0xca0/0xef0 mm/memory.c:3510
 handle_pte_fault mm/memory.c:5049 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x133c/0x2fd4 mm/memory.c:5294
 __do_page_fault arch/arm64/mm/fault.c:499 [inline]
 do_page_fault+0x310/0x99c arch/arm64/mm/fault.c:583
 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:803
 el0_da+0x70/0x154 arch/arm64/kernel/entry-common.c:515
 el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
INFO: task syz.3.173:5263 blocked for more than 143 seconds.
      Not tainted 6.1.143-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.173       state:D stack:0     pid:5263  ppid:4306   flags:0x00000009
Call trace:
 __switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
 schedule+0xc4/0x170 kernel/sched/core.c:6637
 wait_on_state fs/btrfs/extent-io-tree.c:709 [inline]
 wait_extent_bit+0x38c/0x4cc fs/btrfs/extent-io-tree.c:742
 lock_extent+0xe0/0x14c fs/btrfs/extent-io-tree.c:1657
 btrfs_page_mkwrite+0x5b4/0xb78 fs/btrfs/inode.c:8622
 do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
 wp_page_shared+0x148/0x550 mm/memory.c:3360
 do_wp_page+0xca0/0xef0 mm/memory.c:3510
 handle_pte_fault mm/memory.c:5049 [inline]
 __handle_mm_fault mm/memory.c:5173 [inline]
 handle_mm_fault+0x133c/0x2fd4 mm/memory.c:5294
 __do_page_fault arch/arm64/mm/fault.c:499 [inline]
 do_page_fault+0x310/0x99c arch/arm64/mm/fault.c:583
 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:803
 el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:367
 el1h_64_sync_handler+0x80/0xcc arch/arm64/kernel/entry-common.c:427
 el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:580
 __arch_copy_to_user+0x88/0x234 arch/arm64/lib/copy_template.S:90
 emit_last_fiemap_cache fs/btrfs/extent_io.c:3595 [inline]
 extent_fiemap+0x12ec/0x158c fs/btrfs/extent_io.c:4126
 btrfs_fiemap+0x128/0x194 fs/btrfs/inode.c:8294
 ioctl_fiemap fs/ioctl.c:219 [inline]
 do_vfs_ioctl+0x1694/0x206c fs/ioctl.c:810
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0xe4/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffff800015287770 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xbb4 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffff800015287f90 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x40/0xbb4 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffff800015286e00 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:349
2 locks held by getty/4073:
 #0: ffff0000d6741098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80001ce862f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x2ec/0xf9c drivers/tty/n_tty.c:2198
2 locks held by kworker/u4:13/4974:
3 locks held by syz.3.173/5262:
 #0: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
 #0: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5322 [inline]
 #0: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2e8 mm/memory.c:5384
 #1: ffff0000d01d2558 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
 #2: ffff0000f67c8468 (&ei->i_mmap_lock){++++}-{3:3}, at: btrfs_page_mkwrite+0x458/0xb78 fs/btrfs/inode.c:8611
4 locks held by syz.3.173/5263:
 #0: ffff0000f67c85e0 (&sb->s_type->i_mutex_key#23){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:768 [inline]
 #0: ffff0000f67c85e0 (&sb->s_type->i_mutex_key#23){++++}-{3:3}, at: btrfs_inode_lock+0x64/0xdc fs/btrfs/inode.c:147
 #1: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
 #1: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5322 [inline]
 #1: ffff0000cda15b48 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2e8 mm/memory.c:5384
 #2: ffff0000d01d2558 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x13c/0x358 mm/memory.c:3011
 #3: ffff0000f67c8468 (&ei->i_mmap_lock){++++}-{3:3}, at: btrfs_page_mkwrite+0x458/0xb78 fs/btrfs/inode.c:8611
2 locks held by btrfs-cleaner/5305:
 #0: ffff0000d01d2460 (sb_writers#17){.+.+}-{0:0}, at: cleaner_kthread+0x188/0x374 fs/btrfs/disk-io.c:1843
 #1: ffff0000f67c85e0 (&sb->s_type->i_mutex_key#23){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff0000f67c85e0 (&sb->s_type->i_mutex_key#23){++++}-{3:3}, at: btrfs_inode_lock+0x50/0xdc fs/btrfs/inode.c:155
2 locks held by syz.6.807/8096:
3 locks held by syz.4.810/8098:

=============================================


Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/06 20:18 linux-6.1.y 04d1ccaa9c28 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: task hung in btrfs_page_mkwrite
* Struck through repros no longer work on HEAD.