======================================================
WARNING: possible circular locking dependency detected
6.16.0-syzkaller-11895-gcca7a0aae895-dirty #0 Not tainted
------------------------------------------------------
kworker/u8:3/5875 is trying to acquire lock:
ffff888123f2e510 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x164/0xd70

but task is already holding lock:
ffff88812ad64618 (sb_internal#3){.+.+}-{0:0}, at: btrfs_qgroup_rescan_worker+0x3bc/0x2290

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (sb_internal#3){.+.+}-{0:0}:
       lock_acquire+0x120/0x360
       start_transaction+0x56e/0x1620
       btrfs_dirty_inode+0x9f/0x190
       touch_atime+0x2f9/0x6d0
       btrfs_file_mmap_prepare+0xd5/0x140
       mmap_region+0xb41/0x20c0
       do_mmap+0xc45/0x10d0
       vm_mmap_pgoff+0x2a6/0x4d0
       ksys_mmap_pgoff+0x51f/0x760
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&mm->mmap_lock){++++}-{4:4}:
       lock_acquire+0x120/0x360
       down_read_killable+0x50/0x350
       mmap_read_lock_killable+0x1d/0x70
       lock_mm_and_find_vma+0x2a8/0x300
       do_user_addr_fault+0x331/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30
       filldir+0x2bc/0x6c0
       kernfs_fop_readdir+0x537/0x870
       iterate_dir+0x399/0x570
       __se_sys_getdents+0xe4/0x250
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&root->kernfs_rwsem){++++}-{4:4}:
       lock_acquire+0x120/0x360
       down_write+0x96/0x1f0
       kernfs_add_one+0x41/0x520
       kernfs_create_dir_ns+0xde/0x130
       sysfs_create_dir_ns+0x123/0x280
       kobject_add_internal+0x59f/0xb40
       kobject_init_and_add+0x125/0x190
       btrfs_sysfs_add_qgroups+0x111/0x2b0
       btrfs_quota_enable+0x253/0x2600
       btrfs_ioctl_quota_ctl+0x183/0x1c0
       __se_sys_ioctl+0xfc/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1360
       btrfs_quota_enable+0x28e/0x2600
       btrfs_ioctl_quota_ctl+0x183/0x1c0
       __se_sys_ioctl+0xfc/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_extwriters){++++}-{0:0}:
       lock_acquire+0x120/0x360
       join_transaction+0x1a4/0xd70
       start_transaction+0x6b6/0x1620
       btrfs_rebuild_free_space_tree+0xad/0x760
       btrfs_start_pre_rw_mount+0x128f/0x1bf0
       open_ctree+0x293a/0x3a10
       btrfs_get_tree+0xf55/0x1820
       vfs_get_tree+0x92/0x2b0
       do_new_mount+0x2a2/0x9e0
       __se_sys_mount+0x317/0x410
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (btrfs_trans_num_writers){++++}-{0:0}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       join_transaction+0x182/0xd70
       start_transaction+0x6b6/0x1620
       btrfs_qgroup_rescan_worker+0x3bc/0x2290
       btrfs_work_helper+0x39c/0xc20
       process_scheduled_works+0xae1/0x17b0
       worker_thread+0x8a0/0xda0
       kthread+0x711/0x8a0
       ret_from_fork+0x3fc/0x770
       ret_from_fork_asm+0x1a/0x30

other info that might help us debug this:

Chain exists of:
  btrfs_trans_num_writers --> &mm->mmap_lock --> sb_internal#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_internal#3);
                               lock(&mm->mmap_lock);
                               lock(sb_internal#3);
  rlock(btrfs_trans_num_writers);

 *** DEADLOCK ***

3 locks held by kworker/u8:3/5875:
 #0: ffff8881111dc148 ((wq_completion)btrfs-qgroup-rescan){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc9000326fbc0 ((work_completion)(&work->normal_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff88812ad64618 (sb_internal#3){.+.+}-{0:0}, at: btrfs_qgroup_rescan_worker+0x3bc/0x2290

stack backtrace:
CPU: 1 UID: 0 PID: 5875 Comm: kworker/u8:3 Not tainted 6.16.0-syzkaller-11895-gcca7a0aae895-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: btrfs-qgroup-rescan btrfs_work_helper
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 join_transaction+0x182/0xd70
 start_transaction+0x6b6/0x1620
 btrfs_qgroup_rescan_worker+0x3bc/0x2290
 btrfs_work_helper+0x39c/0xc20
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
BTRFS info (device loop3): qgroup scan completed (inconsistency flag cleared)
