====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.6327/26180 is trying to acquire lock: ffff88807012b480 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:797 [inline] ffff88807012b480 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: lookup_slow+0x46/0x70 fs/namei.c:1687 but task is already holding lock: ffff888060db48e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_free_stale_devices+0x188/0xa90 fs/btrfs/volumes.c:603 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&fs_devs->device_list_mutex){+.+.}-{3:3}: __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 insert_dev_extents fs/btrfs/block-group.c:2399 [inline] btrfs_create_pending_block_groups+0x4da/0xec0 fs/btrfs/block-group.c:2449 __btrfs_end_transaction+0x154/0x650 fs/btrfs/transaction.c:1017 flush_space+0x43c/0xc70 fs/btrfs/space-info.c:674 btrfs_async_reclaim_data_space+0xfb/0x460 fs/btrfs/space-info.c:1169 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 -> #4 (sb_internal#6){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1811 [inline] sb_start_intwrite include/linux/fs.h:1928 [inline] start_transaction+0x5bc/0x1130 fs/btrfs/transaction.c:681 btrfs_dirty_inode+0xc5/0x1c0 fs/btrfs/inode.c:6451 inode_update_time fs/inode.c:1893 [inline] file_update_time+0x3a6/0x440 fs/inode.c:2083 btrfs_page_mkwrite+0x37d/0xc80 fs/btrfs/inode.c:8953 do_page_mkwrite+0x168/0x3c0 mm/memory.c:2922 wp_page_shared+0x16b/0x6d0 mm/memory.c:3259 handle_pte_fault mm/memory.c:4668 [inline] __handle_mm_fault mm/memory.c:4785 [inline] handle_mm_fault+0x1f06/0x4410 mm/memory.c:4883 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1355 handle_page_fault arch/x86/mm/fault.c:1443 [inline] exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606 -> #3 (sb_pagefaults#2){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1811 [inline] sb_start_pagefault include/linux/fs.h:1910 [inline] btrfs_page_mkwrite+0x1b7/0xc80 fs/btrfs/inode.c:8937 do_page_mkwrite+0x168/0x3c0 mm/memory.c:2922 wp_page_shared+0x16b/0x6d0 mm/memory.c:3259 handle_pte_fault mm/memory.c:4668 [inline] __handle_mm_fault mm/memory.c:4785 [inline] handle_mm_fault+0x1f06/0x4410 mm/memory.c:4883 do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1355 handle_page_fault arch/x86/mm/fault.c:1443 [inline] exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606 -> #2 (&mm->mmap_lock){++++}-{3:3}: __might_fault+0xb3/0x110 mm/memory.c:5357 fat_ioctl_filldir+0xcf/0x5b0 fs/fat/dir.c:759 dir_emit_dot include/linux/fs.h:3718 [inline] __fat_readdir+0xeda/0x1670 fs/fat/dir.c:663 fat_ioctl_readdir fs/fat/dir.c:777 [inline] fat_dir_ioctl+0x225/0x320 fs/fat/dir.c:815 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #1 (&sbi->s_lock){+.+.}-{3:3}: __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 vfat_lookup+0xf8/0x510 fs/fat/namei_vfat.c:710 __lookup_slow+0x29d/0x410 fs/namei.c:1671 lookup_slow+0x53/0x70 fs/namei.c:1688 walk_component+0x319/0x460 fs/namei.c:1984 lookup_last fs/namei.c:2439 [inline] path_lookupat+0x169/0x440 fs/namei.c:2463 filename_lookup+0x214/0x540 fs/namei.c:2492 user_path_at_empty+0x40/0x190 fs/namei.c:2891 user_path_at include/linux/namei.h:57 [inline] do_mount fs/namespace.c:3374 [inline] __do_sys_mount fs/namespace.c:3585 [inline] __se_sys_mount+0x2a4/0x3d0 fs/namespace.c:3562 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #0 (&sb->s_type->i_mutex_key#21){++++}-{3:3}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 inode_lock_shared include/linux/fs.h:797 [inline] lookup_slow+0x46/0x70 fs/namei.c:1687 walk_component+0x319/0x460 fs/namei.c:1984 lookup_last fs/namei.c:2439 [inline] path_lookupat+0x169/0x440 fs/namei.c:2463 filename_lookup+0x214/0x540 fs/namei.c:2492 kern_path+0x37/0x190 fs/namei.c:2590 lookup_bdev+0xc5/0x280 block/bdev.c:982 device_matched fs/btrfs/volumes.c:568 [inline] btrfs_free_stale_devices+0x6ec/0xa90 fs/btrfs/volumes.c:608 btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1431 btrfs_control_ioctl+0x10a/0x220 fs/btrfs/super.c:2450 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Chain exists of: &sb->s_type->i_mutex_key#21 --> sb_internal#6 --> &fs_devs->device_list_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_devs->device_list_mutex); lock(sb_internal#6); lock(&fs_devs->device_list_mutex); lock(&sb->s_type->i_mutex_key#21); *** DEADLOCK *** 2 locks held by syz.3.6327/26180: #0: ffffffff8c8089a8 (uuid_mutex){+.+.}-{3:3}, at: btrfs_forget_devices+0x1a/0x80 fs/btrfs/volumes.c:1430 #1: ffff888060db48e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: btrfs_free_stale_devices+0x188/0xa90 fs/btrfs/volumes.c:603 stack backtrace: CPU: 0 PID: 26180 Comm: syz.3.6327 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498 inode_lock_shared include/linux/fs.h:797 [inline] lookup_slow+0x46/0x70 fs/namei.c:1687 walk_component+0x319/0x460 fs/namei.c:1984 lookup_last fs/namei.c:2439 [inline] path_lookupat+0x169/0x440 fs/namei.c:2463 filename_lookup+0x214/0x540 fs/namei.c:2492 kern_path+0x37/0x190 fs/namei.c:2590 lookup_bdev+0xc5/0x280 block/bdev.c:982 device_matched fs/btrfs/volumes.c:568 [inline] btrfs_free_stale_devices+0x6ec/0xa90 fs/btrfs/volumes.c:608 btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1431 btrfs_control_ioctl+0x10a/0x220 fs/btrfs/super.c:2450 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f2cb0f12819 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:00007f2caf16c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f2cb118bfa0 RCX: 00007f2cb0f12819 RDX: 00002000000004c0 RSI: 0000000050009405 RDI: 0000000000000004 RBP: 00007f2cb0fa8c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f2cb118c038 R14: 00007f2cb118bfa0 R15: 00007ffd1aada908