======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.356/8858 is trying to acquire lock:
ffff88805e9ba360 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}, at: btrfs_quota_enable+0x2b1/0x1e20 fs/btrfs/qgroup.c:1061

but task is already holding lock:
ffff88805e9bb1b8 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x5f7/0xc60 fs/btrfs/transaction.c:299

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #6 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x18a/0xc60 fs/btrfs/transaction.c:324
       start_transaction+0x73f/0x1880 fs/btrfs/transaction.c:720
       btrfs_symlink+0x405/0x920 fs/btrfs/inode.c:8879
       vfs_symlink+0x18b/0x330 fs/namei.c:5660
       filename_symlinkat+0x1cd/0x420 fs/namei.c:5685
       __do_sys_symlinkat fs/namei.c:5705 [inline]
       __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5700
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (btrfs_trans_num_writers){++++}-{0:0}:
       __lock_release kernel/locking/lockdep.c:5574 [inline]
       lock_release+0x199/0x3c0 kernel/locking/lockdep.c:5889
       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:1097
       btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6273
       file_update_time_flags+0x2d5/0x4b0 fs/inode.c:2485
       btrfs_page_mkwrite+0x608/0x1a50 fs/btrfs/file.c:1904
       do_page_mkwrite+0x14a/0x310 mm/memory.c:3684
       wp_page_shared mm/memory.c:4085 [inline]
       do_wp_page+0x1f32/0x3d90 mm/memory.c:4304
       handle_pte_fault mm/memory.c:6395 [inline]
       __handle_mm_fault mm/memory.c:6517 [inline]
       handle_mm_fault+0xa03/0x13f0 mm/memory.c:6686
       do_user_addr_fault+0xa4d/0x1340 arch/x86/mm/fault.c:1343
       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

-> #4 (sb_pagefaults#3){.+.+}-{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+0x32b/0x1a50 fs/btrfs/file.c:1863
       do_page_mkwrite+0x14a/0x310 mm/memory.c:3684
       wp_page_shared mm/memory.c:4085 [inline]
       do_wp_page+0x1f32/0x3d90 mm/memory.c:4304
       handle_pte_fault mm/memory.c:6395 [inline]
       __handle_mm_fault mm/memory.c:6517 [inline]
       handle_mm_fault+0xa03/0x13f0 mm/memory.c:6686
       do_user_addr_fault+0xa4d/0x1340 arch/x86/mm/fault.c:1343
       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

-> #3 (vm_lock){++++}-{0:0}:
       __vma_start_exclude_readers+0x283/0x930 mm/mmap_lock.c:125
       __vma_start_write+0xdc/0x290 mm/mmap_lock.c:148
       vma_start_write include/linux/mmap_lock.h:303 [inline]
       mprotect_fixup+0x761/0xb10 mm/mprotect.c:801
       setup_arg_pages+0x658/0xbd0 fs/exec.c:674
       load_elf_binary+0xc85/0x2970 fs/binfmt_elf.c:1028
       search_binary_handler fs/exec.c:1694 [inline]
       exec_binprm fs/exec.c:1726 [inline]
       bprm_execve+0x926/0x14b0 fs/exec.c:1778
       kernel_execve+0x8c3/0x9c0 fs/exec.c:1922
       try_to_run_init_process+0x13/0x60 init/main.c:1476
       kernel_init+0xad/0x1d0 init/main.c:1604
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&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:601
       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+0x341/0x1340 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
       filldir64+0x2bc/0x620 fs/readdir.c:-1
       dir_emit include/linux/fs.h:3587 [inline]
       kernfs_fop_readdir+0x583/0x960 fs/kernfs/dir.c:1999
       iterate_dir+0x2f1/0x4e0 fs/readdir.c:110
       __do_sys_getdents64 fs/readdir.c:399 [inline]
       __se_sys_getdents64+0xf1/0x280 fs/readdir.c:384
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x3a/0x50 kernel/locking/rwsem.c:1631
       kernfs_add_one+0x41/0x5e0 fs/kernfs/dir.c:825
       kernfs_create_dir_ns+0x1a1/0x230 fs/kernfs/dir.c:1130
       sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x62c/0xce0 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_init_and_add+0x12b/0x1a0 lib/kobject.c:457
       btrfs_sysfs_add_qgroups+0x118/0x2f0 fs/btrfs/sysfs.c:2604
       btrfs_quota_enable+0x274/0x1e20 fs/btrfs/qgroup.c:1032
       btrfs_ioctl_quota_ctl+0x189/0x1f0 fs/btrfs/ioctl.c:3567
       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:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
       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+0x1520/0x2ce0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
       btrfs_quota_enable+0x2b1/0x1e20 fs/btrfs/qgroup.c:1061
       btrfs_ioctl_quota_ctl+0x189/0x1f0 fs/btrfs/ioctl.c:3567
       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:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &fs_info->qgroup_ioctl_lock --> btrfs_trans_num_writers --> btrfs_trans_num_extwriters

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(btrfs_trans_num_extwriters);
                               lock(btrfs_trans_num_writers);
                               lock(btrfs_trans_num_extwriters);
  lock(&fs_info->qgroup_ioctl_lock);

 *** DEADLOCK ***

5 locks held by syz.4.356/8858:
 #0: ffff88805d62c500 (sb_writers#20){.+.+}-{0:0}, at: mnt_want_write_file+0x63/0x210 fs/namespace.c:538
 #1: ffff88805e9b91b8 (&fs_info->subvol_sem){+.+.}-{4:4}, at: btrfs_ioctl_quota_ctl+0x17e/0x1f0 fs/btrfs/ioctl.c:3566
 #2: ffff88805d62c7f0 (sb_internal#3){.+.+}-{0:0}, at: btrfs_quota_enable+0x2a4/0x1e20 fs/btrfs/qgroup.c:1059
 #3: ffff88805e9bb190 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x5f7/0xc60 fs/btrfs/transaction.c:299
 #4: ffff88805e9bb1b8 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x5f7/0xc60 fs/btrfs/transaction.c:299

stack backtrace:
CPU: 0 UID: 0 PID: 8858 Comm: syz.4.356 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 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+0x1520/0x2ce0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
 btrfs_quota_enable+0x2b1/0x1e20 fs/btrfs/qgroup.c:1061
 btrfs_ioctl_quota_ctl+0x189/0x1f0 fs/btrfs/ioctl.c:3567
 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:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb8de2bde59
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:00007fb8dc516028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb8de545fa0 RCX: 00007fb8de2bde59
RDX: 0000200000000580 RSI: 00000000c0109428 RDI: 0000000000000003
RBP: 00007fb8de353e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb8de546038 R14: 00007fb8de545fa0 R15: 00007ffd7c073978
 </TASK>