============================================
WARNING: possible recursive locking detected
6.15.0-rc2-syzkaller-00048-gc62f4b82d571 #0 Not tainted
--------------------------------------------
syz.6.233/6820 is trying to acquire lock:
ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_free_blocks fs/udf/balloc.c:375 [inline]
ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0x879/0x11c0 fs/udf/balloc.c:677

but task is already holding lock:
ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:516 [inline]
ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x304/0xbc0 fs/udf/balloc.c:701

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.6.233/6820:
 #0: ffff88803161e420 (sb_writers#14){.+.+}-{0:0}, at: splice_direct_to_actor+0x345/0xa30 fs/splice.c:1102
 #1: ffff888077e8e240 (&sb->s_type->i_mutex_key#21){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #1: ffff888077e8e240 (&sb->s_type->i_mutex_key#21){+.+.}-{4:4}, at: udf_file_write_iter+0x6d/0x7b0 fs/udf/file.c:95
 #2: ffff888077e8e070 (&ei->i_data_sem#2){++++}-{4:4}, at: udf_map_block+0x159/0x5b0 fs/udf/inode.c:439
 #3: ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:516 [inline]
 #3: ffff888078b78d28 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x304/0xbc0 fs/udf/balloc.c:701

stack backtrace:
CPU: 0 UID: 0 PID: 6820 Comm: syz.6.233 Not tainted 6.15.0-rc2-syzkaller-00048-gc62f4b82d571 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_deadlock_bug+0x1e9/0x240 kernel/locking/lockdep.c:3042
 check_deadlock kernel/locking/lockdep.c:3094 [inline]
 validate_chain kernel/locking/lockdep.c:3896 [inline]
 __lock_acquire+0xff7/0x1ba0 kernel/locking/lockdep.c:5235
 lock_acquire kernel/locking/lockdep.c:5866 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
 udf_table_free_blocks fs/udf/balloc.c:375 [inline]
 udf_free_blocks+0x879/0x11c0 fs/udf/balloc.c:677
 udf_delete_aext+0x461/0xd80 fs/udf/inode.c:2373
 udf_table_prealloc_blocks fs/udf/balloc.c:543 [inline]
 udf_prealloc_blocks+0xad5/0xbc0 fs/udf/balloc.c:701
 udf_prealloc_extents fs/udf/inode.c:1053 [inline]
 inode_getblk+0x25cb/0x4100 fs/udf/inode.c:911
 udf_map_block+0x2dd/0x5b0 fs/udf/inode.c:447
 __udf_get_block+0x98/0x330 fs/udf/inode.c:461
 __block_write_begin_int+0x4f4/0x16d0 fs/buffer.c:2116
 block_write_begin+0x9a/0x1d0 fs/buffer.c:2227
 udf_write_begin+0x1c7/0x270 fs/udf/inode.c:256
 generic_perform_write+0x3d0/0x930 mm/filemap.c:4102
 __generic_file_write_iter+0x1f7/0x240 mm/filemap.c:4219
 udf_file_write_iter+0x233/0x7b0 fs/udf/file.c:111
 iter_file_splice_write+0x91f/0x1150 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x192/0x6c0 fs/splice.c:1158
 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0x174/0x240 fs/splice.c:1227
 do_sendfile+0xafd/0xe50 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1415
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f656ad8e169
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:00007f656bc96038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f656afb6080 RCX: 00007f656ad8e169
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007f656ae10a68 R08: 0000000000000000 R09: 0000000000000000
R10: 0001000000201005 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f656afb6080 R15: 00007ffd5ab86a18
 </TASK>