============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5323 is trying to acquire lock:
ffff888039079920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_free_blocks fs/udf/balloc.c:376 [inline]
ffff888039079920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0xa8c/0x1900 fs/udf/balloc.c:678

but task is already holding lock:
ffff888039079920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_new_block fs/udf/balloc.c:582 [inline]
ffff888039079920 (&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

4 locks held by syz.0.0/5323:
 #0: ffff888032c16450 (sb_writers#12){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x160 fs/splice.c:1158
 #1: ffff888011ba3c90 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #1: ffff888011ba3c90 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: udf_file_write_iter+0x75/0x6c0 fs/udf/file.c:96
 #2: ffff888011ba3a70 (&ei->i_data_sem#3){++++}-{4:4}, at: udf_map_block+0x29c/0x4280 fs/udf/inode.c:445
 #3: ffff888039079920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_new_block fs/udf/balloc.c:582 [inline]
 #3: ffff888039079920 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_new_block+0xfb7/0x1c00 fs/udf/balloc.c:726

stack backtrace:
CPU: 0 UID: 0 PID: 5323 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
 inode_getblk fs/udf/inode.c:900 [inline]
 udf_map_block+0x135a/0x4280 fs/udf/inode.c:453
 __udf_get_block+0x52/0x250 fs/udf/inode.c:467
 get_more_blocks fs/direct-io.c:644 [inline]
 do_direct_IO fs/direct-io.c:932 [inline]
 __blockdev_direct_IO+0x1590/0x3380 fs/direct-io.c:1236
 blockdev_direct_IO include/linux/fs.h:3130 [inline]
 udf_direct_IO+0x139/0x200 fs/udf/inode.c:311
 generic_file_direct_write+0x1d0/0x3f0 mm/filemap.c:4292
 __generic_file_write_iter+0x11d/0x230 mm/filemap.c:4461
 udf_file_write_iter+0x2e8/0x6c0 fs/udf/file.c:112
 iter_file_splice_write+0xa31/0x1240 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x101/0x160 fs/splice.c:1159
 splice_direct_to_actor+0x57b/0xcb0 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x195/0x290 fs/splice.c:1228
 do_sendfile+0x52e/0x7c0 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64+0x144/0x1a0 fs/read_write.c:1418
 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: 0033:0x7f0a5319de59
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:00007f0a53fb9fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f0a53426090 RCX: 00007f0a5319de59
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000007
RBP: 00007f0a53233e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0a53426128 R14: 00007f0a53426090 R15: 00007ffe2fe77468
 </TASK>