============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.1.22/5967 is trying to acquire lock:
ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_table_free_blocks fs/udf/balloc.c:392 [inline]
ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_free_blocks+0x992/0x17d0 fs/udf/balloc.c:694

but task is already holding lock:
ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_table_prealloc_blocks fs/udf/balloc.c:533 [inline]
ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_prealloc_blocks+0x7e6/0xf30 fs/udf/balloc.c:718

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.1.22/5967:
 #0: ffff8880619da418 (sb_writers#13){.+.+}-{0:0}, at: do_sendfile+0x5cf/0xef0 fs/read_write.c:1253
 #1: ffff88805d632f90 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #1: ffff88805d632f90 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: udf_file_write_iter+0x6e/0x610 fs/udf/file.c:95
 #2: ffff88805d632da8 (&ei->i_data_sem#2){++++}-{3:3}, at: udf_map_block+0x2a5/0x42e0 fs/udf/inode.c:443
 #3: ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_table_prealloc_blocks fs/udf/balloc.c:533 [inline]
 #3: ffff88802ba4cd28 (&sbi->s_alloc_mutex){+.+.}-{3:3}, at: udf_prealloc_blocks+0x7e6/0xf30 fs/udf/balloc.c:718

stack backtrace:
CPU: 0 PID: 5967 Comm: syz.1.22 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_deadlock kernel/locking/lockdep.c:3062 [inline]
 validate_chain kernel/locking/lockdep.c:3856 [inline]
 __lock_acquire+0x5dbc/0x7d40 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x136/0xcc0 kernel/locking/mutex.c:747
 udf_table_free_blocks fs/udf/balloc.c:392 [inline]
 udf_free_blocks+0x992/0x17d0 fs/udf/balloc.c:694
 udf_delete_aext+0x4fc/0xbd0 fs/udf/inode.c:2376
 udf_table_prealloc_blocks fs/udf/balloc.c:560 [inline]
 udf_prealloc_blocks+0xa5c/0xf30 fs/udf/balloc.c:718
 udf_prealloc_extents fs/udf/inode.c:1057 [inline]
 inode_getblk fs/udf/inode.c:915 [inline]
 udf_map_block+0x1eda/0x42e0 fs/udf/inode.c:451
 __udf_get_block+0x53/0x250 fs/udf/inode.c:465
 __block_write_begin_int+0x57f/0x1af0 fs/buffer.c:2124
 __block_write_begin fs/buffer.c:2173 [inline]
 block_write_begin+0x9a/0x1e0 fs/buffer.c:2234
 udf_write_begin+0x1c0/0x420 fs/udf/inode.c:261
 generic_perform_write+0x2fe/0x5c0 mm/filemap.c:4036
 __generic_file_write_iter+0x1ac/0x230 mm/filemap.c:4128
 udf_file_write_iter+0x2b5/0x610 fs/udf/file.c:111
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x738/0xc30 fs/read_write.c:860
 iter_file_splice_write+0x6a3/0xcb0 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0xe8/0x130 fs/splice.c:1142
 splice_direct_to_actor+0x304/0x8c0 fs/splice.c:1088
 do_splice_direct+0x1d5/0x2f0 fs/splice.c:1194
 do_sendfile+0x5f2/0xef0 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64+0x145/0x1a0 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff5dd99c819
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:00007ff5de84f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007ff5ddc15fa0 RCX: 00007ff5dd99c819
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 00007ff5dda32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000800000009 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff5ddc16038 R14: 00007ff5ddc15fa0 R15: 00007ffdc7388d48
 </TASK>