syzbot

IPVS: ftp: loaded support on port[0] = 21
============================================
WARNING: possible recursive locking detected
4.19.211-syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:4/1530 is trying to acquire lock:
000000008d64b6c6 (&tree->tree_lock/1){+.+.}, at: hfs_find_init+0x17e/0x230 fs/hfs/bfind.c:33

but task is already holding lock:
000000008d64b6c6 (&tree->tree_lock/1){+.+.}, at: hfs_find_init+0x17e/0x230 fs/hfs/bfind.c:33

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

       CPU0
       ----
  lock(&tree->tree_lock/1);
  lock(&tree->tree_lock/1);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by kworker/u4:4/1530:
 #0: 00000000a9ed9130 ((wq_completion)"writeback"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2124
 #1: 00000000dc3b79d5 ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2128
 #2: 000000008d64b6c6 (&tree->tree_lock/1){+.+.}, at: hfs_find_init+0x17e/0x230 fs/hfs/bfind.c:33
 #3: 0000000083ad5da7 (&HFS_I(tree->inode)->extents_lock){+.+.}, at: hfs_extend_file+0x93/0xac0 fs/hfs/extent.c:397

stack backtrace:
CPU: 1 PID: 1530 Comm: kworker/u4:4 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline]
 check_deadlock kernel/locking/lockdep.c:1808 [inline]
 validate_chain kernel/locking/lockdep.c:2404 [inline]
 __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 __mutex_lock_common kernel/locking/mutex.c:937 [inline]
 __mutex_lock+0xd7/0x1190 kernel/locking/mutex.c:1078
 hfs_find_init+0x17e/0x230 fs/hfs/bfind.c:33
 hfs_ext_read_extent+0x191/0xa20 fs/hfs/extent.c:200
 hfs_extend_file+0x4a0/0xac0 fs/hfs/extent.c:401
 hfs_bmap_reserve+0x241/0x390 fs/hfs/btree.c:231
 __hfs_ext_write_extent+0x3c1/0x510 fs/hfs/extent.c:121
 hfs_ext_write_extent fs/hfs/extent.c:144 [inline]
 hfs_ext_write_extent+0x1a2/0x1f0 fs/hfs/extent.c:135
 hfs_write_inode+0x8f/0x930 fs/hfs/inode.c:426
 write_inode fs/fs-writeback.c:1244 [inline]
 __writeback_single_inode+0x733/0x11d0 fs/fs-writeback.c:1442
 writeback_sb_inodes+0x537/0xef0 fs/fs-writeback.c:1647
 wb_writeback+0x28d/0xcc0 fs/fs-writeback.c:1820
 wb_do_writeback fs/fs-writeback.c:1965 [inline]
 wb_workfn+0x29b/0x1250 fs/fs-writeback.c:2006
 process_one_work+0x864/0x1570 kernel/workqueue.c:2153
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415