BTRFS info (device loop1): enabling ssd optimizations BTRFS info (device loop1): turning on async discard BTRFS info (device loop1): enabling free space tree ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.1474/26162 is trying to acquire lock: ffff88813ff77238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x6f0 fs/kernfs/dir.c:825 but task is already holding lock: ffff888063f130c8 (&fs_devs->device_list_mutex){+.+.}-{4:4}, at: btrfs_init_new_device+0xa3a/0x1ca0 fs/btrfs/volumes.c:3027 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&fs_devs->device_list_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:561 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:580 btrfs_init_new_device+0xa3a/0x1ca0 fs/btrfs/volumes.c:3027 btrfs_ioctl_add_dev+0x1ad/0x640 fs/btrfs/ioctl.c:2571 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x18a/0xc60 fs/btrfs/transaction.c:324 start_transaction+0x6ed/0x17d0 fs/btrfs/transaction.c:729 btrfs_ioctl_subvol_setflags+0x46b/0x830 fs/btrfs/ioctl.c:1377 btrfs_ioctl+0xa22/0xd60 fs/btrfs/ioctl.c:5568 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5627 [inline] lock_release+0x1a3/0x3c0 kernel/locking/lockdep.c:5964 percpu_up_read include/linux/percpu-rwsem.h:114 [inline] __sb_end_write include/linux/fs/super.h:14 [inline] sb_end_intwrite+0x26/0x190 include/linux/fs/super.h:101 __btrfs_end_transaction+0x23f/0x640 fs/btrfs/transaction.c:1106 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6479 touch_atime+0x2f8/0x670 fs/inode.c:2325 file_accessed include/linux/fs.h:2277 [inline] btrfs_file_mmap_prepare+0x189/0x200 fs/btrfs/file.c:2003 vfs_mmap_prepare include/linux/fs.h:2069 [inline] call_mmap_prepare mm/vma.c:2784 [inline] __mmap_region mm/vma.c:2873 [inline] mmap_region+0xebb/0x25c0 mm/vma.c:2974 do_mmap+0xe0e/0x1310 mm/mmap.c:573 vm_mmap_pgoff+0x275/0x4e0 mm/util.c:581 ksys_mmap_pgoff+0x4a6/0x720 mm/mmap.c:619 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&mm->mmap_lock){++++}-{4:4}: down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1599 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d6/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x343/0x1340 arch/x86/mm/fault.c:1366 handle_page_fault arch/x86/mm/fault.c:1483 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595 filldir+0x2b2/0x630 fs/readdir.c:-1 dir_emit include/linux/fs.h:3607 [inline] kernfs_fop_readdir+0x583/0x960 fs/kernfs/dir.c:1999 iterate_dir+0x2f1/0x4e0 fs/readdir.c:110 __do_sys_getdents fs/readdir.c:319 [inline] __se_sys_getdents+0xf1/0x270 fs/readdir.c:304 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&root->kernfs_rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 down_write+0x3a/0x50 kernel/locking/rwsem.c:1631 kernfs_add_one+0x41/0x6f0 fs/kernfs/dir.c:825 kernfs_create_link+0x161/0x200 fs/kernfs/symlink.c:48 sysfs_do_create_link_sd+0x83/0x110 fs/sysfs/symlink.c:44 btrfs_sysfs_add_device+0x13f/0x650 fs/btrfs/sysfs.c:2155 btrfs_init_new_device+0xeb6/0x1ca0 fs/btrfs/volumes.c:3069 btrfs_ioctl_add_dev+0x1ad/0x640 fs/btrfs/ioctl.c:2571 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &root->kernfs_rwsem --> btrfs_trans_num_extwriters --> &fs_devs->device_list_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_devs->device_list_mutex); lock(btrfs_trans_num_extwriters); lock(&fs_devs->device_list_mutex); lock(&root->kernfs_rwsem); *** DEADLOCK *** locks held by syz.1.1474/26162: 4, last CPU#1: #0: ffff888064798800 (sb_internal#4){.+.+}-{0:0}, at: btrfs_init_new_device+0x728/0x1ca0 fs/btrfs/volumes.c:2991 #1: ffff88804cbeb190 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x5f7/0xc60 fs/btrfs/transaction.c:299 #2: ffff88804cbeb1b8 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x5f7/0xc60 fs/btrfs/transaction.c:299 #3: ffff888063f130c8 (&fs_devs->device_list_mutex){+.+.}-{4:4}, at: btrfs_init_new_device+0xa3a/0x1ca0 fs/btrfs/volumes.c:3027 stack backtrace: CPU: 1 UID: 0 PID: 26162 Comm: syz.1.1474 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 down_write+0x3a/0x50 kernel/locking/rwsem.c:1631 kernfs_add_one+0x41/0x6f0 fs/kernfs/dir.c:825 kernfs_create_link+0x161/0x200 fs/kernfs/symlink.c:48 sysfs_do_create_link_sd+0x83/0x110 fs/sysfs/symlink.c:44 btrfs_sysfs_add_device+0x13f/0x650 fs/btrfs/sysfs.c:2155 btrfs_init_new_device+0xeb6/0x1ca0 fs/btrfs/volumes.c:3069 btrfs_ioctl_add_dev+0x1ad/0x640 fs/btrfs/ioctl.c:2571 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcf4d78e159 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:00007fcf4b9e6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fcf4da15fa0 RCX: 00007fcf4d78e159 RDX: 0000200000001000 RSI: 000000005000940a RDI: 0000000000000004 RBP: 00007fcf4d82506b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fcf4da16038 R14: 00007fcf4da15fa0 R15: 00007ffc04966258 BTRFS info (device loop1): disk added /dev/nullb0