======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.5.375/8912 is trying to acquire lock:
ffff88802a1f9760 (&mm->mmap_lock){++++}-{4:4}, at: upgrade_mmap_lock_carefully+0xba/0x1c0

but task is already holding lock:
ffff8881110759f0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: iterate_dir+0x292/0x570

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&type->i_mutex_dir_key#3){++++}-{4:4}:
       lock_acquire+0x120/0x360
       down_read+0x46/0x2e0
       lookup_slow+0x46/0x70
       walk_component+0x2d2/0x400
       path_lookupat+0x163/0x430
       filename_lookup+0x212/0x570
       kern_path+0x35/0x50
       device_list_add+0xe2a/0x22a0
       btrfs_scan_one_device+0x3ee/0x650
       btrfs_control_ioctl+0x11f/0x360
       __se_sys_ioctl+0xfc/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1350
       btrfs_create_pending_block_groups+0x5f8/0x1780
       __btrfs_end_transaction+0x140/0x640
       flush_space+0x315/0xcd0
       do_async_reclaim_data_space+0x11c/0x520
       btrfs_async_reclaim_data_space+0x41/0x90
       process_scheduled_works+0xae1/0x17b0
       worker_thread+0x8a0/0xda0
       kthread+0x711/0x8a0
       ret_from_fork+0x3fc/0x770
       ret_from_fork_asm+0x1a/0x30

-> #3 (btrfs_trans_num_extwriters){++++}-{0:0}:
       lock_acquire+0x120/0x360
       join_transaction+0x1a4/0xd70
       start_transaction+0x6b6/0x1620
       btrfs_dirty_inode+0x9f/0x190
       touch_atime+0x2f9/0x6d0
       filemap_read+0x1002/0x11a0
       __kernel_read+0x4cf/0x960
       integrity_kernel_read+0x89/0xd0
       ima_calc_file_hash+0x85e/0x16f0
       ima_collect_measurement+0x428/0x8e0
       process_measurement+0x1121/0x1a40
       ima_file_check+0xd7/0x120
       security_file_post_open+0xbb/0x290
       path_openat+0x2f26/0x3830
       do_filp_open+0x1fa/0x410
       do_sys_openat2+0x121/0x1c0
       __x64_sys_openat+0x138/0x170
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (btrfs_trans_num_writers){++++}-{0:0}:
       reacquire_held_locks+0x127/0x1d0
       lock_release+0x1b4/0x3e0
       sb_end_intwrite+0x26/0x1c0
       __btrfs_end_transaction+0x248/0x640
       btrfs_dirty_inode+0x14c/0x190
       file_update_time+0x347/0x490
       btrfs_page_mkwrite+0x5c8/0x1a70
       do_page_mkwrite+0x14d/0x310
       do_wp_page+0x268d/0x5800
       __handle_mm_fault+0x1033/0x5440
       handle_mm_fault+0x40a/0x8e0
       do_user_addr_fault+0xa81/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30

-> #1 (sb_pagefaults#2){.+.+}-{0:0}:
       lock_acquire+0x120/0x360
       btrfs_page_mkwrite+0x317/0x1a70
       do_page_mkwrite+0x14d/0x310
       __handle_mm_fault+0x1916/0x5440
       handle_mm_fault+0x40a/0x8e0
       do_user_addr_fault+0x764/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30

-> #0 (&mm->mmap_lock){++++}-{4:4}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       down_write_killable+0xa7/0x230
       upgrade_mmap_lock_carefully+0xba/0x1c0
       lock_mm_and_find_vma+0x10a/0x300
       do_user_addr_fault+0x331/0x1390
       exc_page_fault+0x76/0xf0
       asm_exc_page_fault+0x26/0x30
       filldir64+0x2c7/0x690
       ext4_readdir+0x1593/0x3b60
       iterate_dir+0x399/0x570
       __se_sys_getdents64+0xe4/0x260
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &mm->mmap_lock --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&type->i_mutex_dir_key#3);
                               lock(&fs_devs->device_list_mutex);
                               lock(&type->i_mutex_dir_key#3);
  lock(&mm->mmap_lock);

 *** DEADLOCK ***

2 locks held by syz.5.375/8912:
 #0: ffff88810863faf8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320
 #1: ffff8881110759f0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: iterate_dir+0x292/0x570

stack backtrace:
CPU: 0 UID: 0 PID: 8912 Comm: syz.5.375 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
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
 down_write_killable+0xa7/0x230
 upgrade_mmap_lock_carefully+0xba/0x1c0
 lock_mm_and_find_vma+0x10a/0x300
 do_user_addr_fault+0x331/0x1390
 exc_page_fault+0x76/0xf0
 asm_exc_page_fault+0x26/0x30
RIP: 0010:filldir64+0x2c7/0x690
Code: e8 48 8b 44 24 50 49 89 44 24 08 48 8b 4c 24 08 48 8b 44 24 58 48 89 01 48 8b 04 24 8b 54 24 14 49 bc 00 00 00 00 00 fc ff df <66> 89 41 10 80 e2 0f 88 51 12 49 63 ee c6 44 29 13 00 4c 8d 79 13
RSP: 0018:ffffc90002f97a48 EFLAGS: 00010283
RAX: 0000000000000020 RBX: ffffc90002f97e38 RCX: 0000200000000ff0
RDX: 0000000000000008 RSI: 0000200000000fd0 RDI: 0000200000001010
RBP: 00007ffffffff000 R08: ffff88810b820007 R09: 1ffff11021704000
R10: dffffc0000000000 R11: ffffed1021704001 R12: dffffc0000000000
R13: ffff888127082044 R14: 0000000000000005 R15: 0000200000001010
 ext4_readdir+0x1593/0x3b60
 iterate_dir+0x399/0x570
 __se_sys_getdents64+0xe4/0x260
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f06abb8eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f06acac9038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f06abdd5fa0 RCX: 00007f06abb8eba9
RDX: 0000000000001000 RSI: 0000200000000f80 RDI: 0000000000000006
RBP: 00007f06abc11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f06abdd6038 R14: 00007f06abdd5fa0 R15: 00007ffe3d47e798
 </TASK>
