============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5325 is trying to acquire lock:
ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_free_blocks fs/udf/balloc.c:376 [inline]
ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0xa8c/0x1900 fs/udf/balloc.c:678

but task is already holding lock:
ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_new_block fs/udf/balloc.c:582 [inline]
ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_new_block+0xfb7/0x1c00 fs/udf/balloc.c:726

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sbi->s_alloc_mutex);
  lock(&sbi->s_alloc_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.0.0/5325:
 #0: ffff888012020450 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494
 #1: ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_new_block fs/udf/balloc.c:582 [inline]
 #1: ffff888040b06920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_new_block+0xfb7/0x1c00 fs/udf/balloc.c:726

stack backtrace:
CPU: 0 UID: 0 PID: 5325 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x24df/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 udf_table_free_blocks fs/udf/balloc.c:376 [inline]
 udf_free_blocks+0xa8c/0x1900 fs/udf/balloc.c:678
 udf_delete_aext+0x4f5/0xc00 fs/udf/inode.c:2381
 udf_table_new_block fs/udf/balloc.c:646 [inline]
 udf_new_block+0x142f/0x1c00 fs/udf/balloc.c:726
 udf_new_inode+0x3bb/0xd60 fs/udf/ialloc.c:67
 udf_tmpfile+0x23/0x120 fs/udf/namei.c:392
 vfs_tmpfile+0x547/0xa10 fs/namei.c:4755
 do_tmpfile+0xd3/0x240 fs/namei.c:4820
 path_openat+0x3079/0x3830 fs/namei.c:4854
 do_file_open+0x23e/0x4a0 fs/namei.c:4892
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_open fs/open.c:1382 [inline]
 __se_sys_open fs/open.c:1378 [inline]
 __x64_sys_open+0x11e/0x150 fs/open.c:1378
 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: 0033:0x7fe43819de99
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:00007fe438fdffe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fe438426090 RCX: 00007fe43819de99
RDX: 0000000000000000 RSI: 0000000000511082 RDI: 0000200000000040
RBP: 00007fe438233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe438426128 R14: 00007fe438426090 R15: 00007ffd0edd4188
 </TASK>