BTRFS info (device loop3): force clearing of disk cache BTRFS info (device loop3): enabling auto defrag BTRFS info (device loop3): max_inline set to 0 ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.3.862/9895 is trying to acquire lock: ffff88801be95180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:809 but task is already holding lock: ffff88804fa35a20 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}, at: btrfs_quota_enable+0x237/0x2850 fs/btrfs/qgroup.c:1030 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 btrfs_create_qgroup+0x55/0x520 fs/btrfs/qgroup.c:1684 create_pending_snapshot+0x6c6/0x37e0 fs/btrfs/transaction.c:1767 create_pending_snapshots+0x17c/0x1c0 fs/btrfs/transaction.c:1965 btrfs_commit_transaction+0xf78/0x3130 fs/btrfs/transaction.c:2463 create_snapshot fs/btrfs/ioctl.c:785 [inline] btrfs_mksubvol+0x9bc/0x10a0 fs/btrfs/ioctl.c:863 btrfs_mksnapshot+0xab/0xf0 fs/btrfs/ioctl.c:905 __btrfs_ioctl_snap_create+0x52e/0x750 fs/btrfs/ioctl.c:1169 btrfs_ioctl_snap_create_v2+0x1f8/0x3b0 fs/btrfs/ioctl.c:1248 btrfs_ioctl+0xa62/0xd00 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&fs_info->reloc_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 btrfs_record_root_in_trans+0x14f/0x180 fs/btrfs/transaction.c:506 start_transaction+0x3a5/0x1790 fs/btrfs/transaction.c:793 create_snapshot fs/btrfs/ioctl.c:770 [inline] btrfs_mksubvol+0x838/0x10a0 fs/btrfs/ioctl.c:863 btrfs_mksnapshot+0xab/0xf0 fs/btrfs/ioctl.c:905 __btrfs_ioctl_snap_create+0x52e/0x750 fs/btrfs/ioctl.c:1169 btrfs_ioctl_snap_create_v2+0x1f8/0x3b0 fs/btrfs/ioctl.c:1248 btrfs_ioctl+0xa62/0xd00 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x1a4/0xd60 fs/btrfs/transaction.c:324 start_transaction+0xb07/0x1790 fs/btrfs/transaction.c:719 create_snapshot fs/btrfs/ioctl.c:770 [inline] btrfs_mksubvol+0x838/0x10a0 fs/btrfs/ioctl.c:863 btrfs_mksnapshot+0xab/0xf0 fs/btrfs/ioctl.c:905 __btrfs_ioctl_snap_create+0x52e/0x750 fs/btrfs/ioctl.c:1169 btrfs_ioctl_snap_create_v2+0x1f8/0x3b0 fs/btrfs/ioctl.c:1248 btrfs_ioctl+0xa62/0xd00 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x199/0x3c0 kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs/super.h:14 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs/super.h:101 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1096 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6451 file_update_time_flags+0x2cf/0x4a0 fs/inode.c:2420 btrfs_page_mkwrite+0x60a/0x1a60 fs/btrfs/file.c:1914 do_page_mkwrite+0x14d/0x310 mm/memory.c:3668 wp_page_shared mm/memory.c:4069 [inline] do_wp_page+0x19ba/0x4cc0 mm/memory.c:4288 handle_pte_fault mm/memory.c:6470 [inline] __handle_mm_fault mm/memory.c:6592 [inline] handle_mm_fault+0x151d/0x3170 mm/memory.c:6761 do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #2 (sb_pagefaults#3){.+.+}-{0:0}: percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs/super.h:19 [inline] sb_start_pagefault include/linux/fs/super.h:159 [inline] btrfs_page_mkwrite+0x351/0x1a60 fs/btrfs/file.c:1873 do_page_mkwrite+0x14d/0x310 mm/memory.c:3668 do_shared_fault mm/memory.c:6012 [inline] do_fault mm/memory.c:6074 [inline] do_pte_missing+0x6dc/0x33f0 mm/memory.c:4550 handle_pte_fault mm/memory.c:6454 [inline] __handle_mm_fault mm/memory.c:6592 [inline] handle_mm_fault+0x1bd7/0x3170 mm/memory.c:6761 do_user_addr_fault+0x75b/0x1340 arch/x86/mm/fault.c:1385 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 -> #1 (&mm->mmap_lock){++++}-{4:4}: down_read_killable+0x50/0x340 kernel/locking/rwsem.c:1593 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 filldir64+0x2be/0x640 fs/readdir.c:370 dir_emit include/linux/fs.h:3572 [inline] kernfs_fop_readdir+0x57b/0x8d0 fs/kernfs/dir.c:1972 iterate_dir+0x399/0x570 fs/readdir.c:110 __do_sys_getdents64 fs/readdir.c:399 [inline] __se_sys_getdents64+0xf1/0x280 fs/readdir.c:384 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&root->kernfs_rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_write+0x96/0x200 kernel/locking/rwsem.c:1625 kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:809 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1111 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x62b/0xd00 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x12b/0x1a0 lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x116/0x2e0 fs/btrfs/sysfs.c:2604 btrfs_quota_enable+0x282/0x2850 fs/btrfs/qgroup.c:1034 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3540 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &root->kernfs_rwsem --> &fs_info->reloc_mutex --> &fs_info->qgroup_ioctl_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->qgroup_ioctl_lock); lock(&fs_info->reloc_mutex); lock(&fs_info->qgroup_ioctl_lock); lock(&root->kernfs_rwsem); *** DEADLOCK *** 3 locks held by syz.3.862/9895: #0: ffff8880610e4410 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x60/0x200 fs/namespace.c:537 #1: ffff88804fa34d18 (&fs_info->subvol_sem){++++}-{4:4}, at: btrfs_ioctl_quota_ctl+0x178/0x1c0 fs/btrfs/ioctl.c:3539 #2: ffff88804fa35a20 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}, at: btrfs_quota_enable+0x237/0x2850 fs/btrfs/qgroup.c:1030 stack backtrace: CPU: 0 UID: 0 PID: 9895 Comm: syz.3.862 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_write+0x96/0x200 kernel/locking/rwsem.c:1625 kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:809 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1111 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x62b/0xd00 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x12b/0x1a0 lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x116/0x2e0 fs/btrfs/sysfs.c:2604 btrfs_quota_enable+0x282/0x2850 fs/btrfs/qgroup.c:1034 btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3540 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa25399c819 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa2548b2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fa253c15fa0 RCX: 00007fa25399c819 RDX: 0000200000000580 RSI: 00000000c0109428 RDI: 0000000000000004 RBP: 00007fa253a32c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa253c16038 R14: 00007fa253c15fa0 R15: 00007fff5183d0a8