syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
kworker/u8:7/27912 is trying to acquire lock:
ffff8880b26cc610 (sb_internal#2){.+.+}-{0:0}, at: btrfs_finish_one_ordered+0x7b0/0x2170 fs/btrfs/inode.c:3163

but task is already holding lock:
ffff88803f136648 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x30b/0x2170 fs/btrfs/inode.c:3125

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (btrfs_ordered_extent){++++}-{0:0}:
       btrfs_start_ordered_extent_nowriteback+0x38c/0x6c0 fs/btrfs/ordered-data.c:891
       btrfs_start_ordered_extent fs/btrfs/ordered-data.h:199 [inline]
       btrfs_wait_ordered_range+0x154/0x260 fs/btrfs/ordered-data.c:943
       btrfs_sync_file+0x6cc/0x1140 fs/btrfs/file.c:1664
       generic_write_sync include/linux/fs.h:2616 [inline]
       btrfs_do_write_iter+0x689/0x820 fs/btrfs/file.c:1470
       iter_file_splice_write+0x972/0x10b0 fs/splice.c:738
       do_splice_from fs/splice.c:938 [inline]
       direct_splice_actor+0x101/0x160 fs/splice.c:1161
       splice_direct_to_actor+0x5a8/0xcc0 fs/splice.c:1105
       do_splice_direct_actor fs/splice.c:1204 [inline]
       do_splice_direct+0x181/0x270 fs/splice.c:1230
       do_sendfile+0x4da/0x7e0 fs/read_write.c:1370
       __do_sys_sendfile64 fs/read_write.c:1431 [inline]
       __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (&ei->i_mmap_lock){++++}-{4:4}:
       down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537
       btrfs_page_mkwrite+0x5f3/0x1a70 fs/btrfs/file.c:1920
       do_page_mkwrite+0x14d/0x310 mm/memory.c:3528
       do_shared_fault mm/memory.c:5831 [inline]
       do_fault mm/memory.c:5893 [inline]
       do_pte_missing+0x795/0x3330 mm/memory.c:4401
       handle_pte_fault mm/memory.c:6273 [inline]
       __handle_mm_fault mm/memory.c:6411 [inline]
       handle_mm_fault+0x1b26/0x32b0 mm/memory.c:6580
       do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387
       handle_page_fault arch/x86/mm/fault.c:1476 [inline]
       exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

-> #6 (sb_pagefaults#4){.+.+}-{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+0x317/0x1a70 fs/btrfs/file.c:1875
       do_page_mkwrite+0x14d/0x310 mm/memory.c:3528
       do_shared_fault mm/memory.c:5831 [inline]
       do_fault mm/memory.c:5893 [inline]
       do_pte_missing+0x795/0x3330 mm/memory.c:4401
       handle_pte_fault mm/memory.c:6273 [inline]
       __handle_mm_fault mm/memory.c:6411 [inline]
       handle_mm_fault+0x1b26/0x32b0 mm/memory.c:6580
       do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387
       handle_page_fault arch/x86/mm/fault.c:1476 [inline]
       exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

-> #5 (&mm->mmap_lock){++++}-{4:4}:
       down_read_killable+0x50/0x350 kernel/locking/rwsem.c:1560
       mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400
       get_mmap_lock_carefully mm/mmap_lock.c:399 [inline]
       lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:450
       do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359
       handle_page_fault arch/x86/mm/fault.c:1476 [inline]
       exc_page_fault+0x71/0xd0 arch/x86/mm/fault.c:1532
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
       filldir+0x2b6/0x6c0 fs/readdir.c:295
       dir_emit include/linux/fs.h:3527 [inline]
       kernfs_fop_readdir+0x537/0x870 fs/kernfs/dir.c:1913
       iterate_dir+0x399/0x570 fs/readdir.c:108
       __do_sys_getdents fs/readdir.c:326 [inline]
       __se_sys_getdents+0xe4/0x250 fs/readdir.c:312
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
       kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:794
       kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1096
       sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x6ab/0xcc0 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_init_and_add+0x125/0x190 lib/kobject.c:457
       btrfs_sysfs_add_qgroups+0x111/0x2b0 fs/btrfs/sysfs.c:2697
       btrfs_quota_enable+0x25d/0x28f0 fs/btrfs/qgroup.c:1002
       btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3613
       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+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
       btrfs_quota_enable+0x29c/0x28f0 fs/btrfs/qgroup.c:1031
       btrfs_ioctl_quota_ctl+0x183/0x1c0 fs/btrfs/ioctl.c:3613
       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+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x1a4/0xd60 fs/btrfs/transaction.c:323
       start_transaction+0x6b7/0x15f0 fs/btrfs/transaction.c:707
       btrfs_create_common+0x146/0x2f0 fs/btrfs/inode.c:6838
       lookup_open fs/namei.c:4440 [inline]
       open_last_lookups fs/namei.c:4540 [inline]
       path_openat+0x18bb/0x3dd0 fs/namei.c:4784
       do_filp_open+0x1fa/0x410 fs/namei.c:4814
       do_sys_openat2+0x121/0x200 fs/open.c:1430
       do_sys_open fs/open.c:1436 [inline]
       __do_sys_openat fs/open.c:1452 [inline]
       __se_sys_openat fs/open.c:1447 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1447
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       join_transaction+0x182/0xd60 fs/btrfs/transaction.c:322
       start_transaction+0x6b7/0x15f0 fs/btrfs/transaction.c:707
       btrfs_create_common+0x146/0x2f0 fs/btrfs/inode.c:6838
       lookup_open fs/namei.c:4440 [inline]
       open_last_lookups fs/namei.c:4540 [inline]
       path_openat+0x18bb/0x3dd0 fs/namei.c:4784
       do_filp_open+0x1fa/0x410 fs/namei.c:4814
       do_sys_openat2+0x121/0x200 fs/open.c:1430
       do_sys_open fs/open.c:1436 [inline]
       __do_sys_openat fs/open.c:1452 [inline]
       __se_sys_openat fs/open.c:1447 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1447
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal#2){.+.+}-{0:0}:
       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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
       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_intwrite include/linux/fs/super.h:177 [inline]
       start_transaction+0x56f/0x15f0 fs/btrfs/transaction.c:701
       btrfs_finish_one_ordered+0x7b0/0x2170 fs/btrfs/inode.c:3163
       btrfs_work_helper+0x38c/0xbf0 fs/btrfs/async-thread.c:312
       process_one_work kernel/workqueue.c:3257 [inline]
       process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
       worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

other info that might help us debug this:

Chain exists of:
  sb_internal#2 --> &ei->i_mmap_lock --> btrfs_ordered_extent

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(btrfs_ordered_extent);
                               lock(&ei->i_mmap_lock);
                               lock(btrfs_ordered_extent);
  rlock(sb_internal#2);

 *** DEADLOCK ***

3 locks held by kworker/u8:7/27912:
 #0: ffff88807afaf148 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline]
 #0: ffff88807afaf148 ((wq_completion)btrfs-endio-write){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x1770 kernel/workqueue.c:3340
 #1: ffffc9000b357bc0 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline]
 #1: ffffc9000b357bc0 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x1770 kernel/workqueue.c:3340
 #2: ffff88803f136648 (btrfs_ordered_extent){++++}-{0:0}, at: btrfs_finish_one_ordered+0x30b/0x2170 fs/btrfs/inode.c:3125

stack backtrace:
CPU: 0 UID: 0 PID: 27912 Comm: kworker/u8:7 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: btrfs-endio-write btrfs_work_helper
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
 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_intwrite include/linux/fs/super.h:177 [inline]
 start_transaction+0x56f/0x15f0 fs/btrfs/transaction.c:701
 btrfs_finish_one_ordered+0x7b0/0x2170 fs/btrfs/inode.c:3163
 btrfs_work_helper+0x38c/0xbf0 fs/btrfs/async-thread.c:312
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>