============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.1.61/6128 is trying to acquire lock:
ffff88801e50bd20 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0xa8c/0x1900

but task is already holding lock:
ffff88801e50bd20 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8ea/0x10e0

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.1.61/6128:
 #0: ffff8881120ec450 (sb_writers#29){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x160
 #1: ffff88801b19c960 (&sb->s_type->i_mutex_key#37){+.+.}-{4:4}, at: udf_file_write_iter+0x75/0x6c0
 #2: ffff88801b19c740 (&ei->i_data_sem#3){++++}-{4:4}, at: udf_map_block+0x29c/0x4280
 #3: ffff88801e50bd20 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8ea/0x10e0

stack backtrace:
CPU: 0 UID: 0 PID: 6128 Comm: syz.1.61 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+0xe8/0x150
 print_deadlock_bug+0x279/0x290
 __lock_acquire+0x24df/0x2cf0
 lock_acquire+0x106/0x350
 __mutex_lock+0x19d/0x1550
 udf_free_blocks+0xa8c/0x1900
 udf_delete_aext+0x4f5/0xc00
 udf_prealloc_blocks+0xbd4/0x10e0
 udf_map_block+0x1e7f/0x4280
 __udf_get_block+0x52/0x250
 __block_write_begin_int+0x6c2/0x1900
 block_write_begin+0x8d/0x120
 udf_write_begin+0x118/0x270
 generic_perform_write+0x2d5/0x8f0
 udf_file_write_iter+0x2e8/0x6c0
 iter_file_splice_write+0xa31/0x1240
 direct_splice_actor+0x101/0x160
 splice_direct_to_actor+0x57b/0xcb0
 do_splice_direct+0x195/0x290
 do_sendfile+0x52e/0x7c0
 __se_sys_sendfile64+0x144/0x1a0
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f075979ce59
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:00007f07579f6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f0759a16090 RCX: 00007f075979ce59
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007f0759832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0001000000201005 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0759a16128 R14: 00007f0759a16090 R15: 00007fffd31454e8
 </TASK>
