syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
btrfs-cleaner/7527 is trying to acquire lock:
ffff0000ce4122a8 (&delayed_node->mutex){+.+.}-{4:4}, at: __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290

but task is already holding lock:
ffff0000df5b0e18 (btrfs-tree-00){++++}-{4:4}, at: btrfs_tree_read_lock_nested+0x44/0x2ec fs/btrfs/locking.c:145

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (btrfs-tree-00){++++}-{4:4}:
       down_read_nested+0x5c/0x30c kernel/locking/rwsem.c:1662
       btrfs_tree_read_lock_nested+0x44/0x2ec fs/btrfs/locking.c:145
       btrfs_tree_read_lock fs/btrfs/locking.h:188 [inline]
       btrfs_read_lock_root_node+0x4c/0xf0 fs/btrfs/locking.c:266
       btrfs_search_slot_get_root fs/btrfs/ctree.c:1766 [inline]
       btrfs_search_slot+0x468/0x2228 fs/btrfs/ctree.c:2090
       btrfs_insert_empty_items+0xa4/0x17c fs/btrfs/ctree.c:4315
       btrfs_insert_delayed_item fs/btrfs/delayed-inode.c:758 [inline]
       btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:835 [inline]
       __btrfs_commit_inode_delayed_items+0x878/0x1788 fs/btrfs/delayed-inode.c:1127
       __btrfs_run_delayed_items+0x1ac/0x514 fs/btrfs/delayed-inode.c:1173
       btrfs_run_delayed_items+0x24/0x34 fs/btrfs/delayed-inode.c:1211
       btrfs_commit_transaction+0x8bc/0x2d30 fs/btrfs/transaction.c:2343
       btrfs_commit_current_transaction+0xac/0xdc fs/btrfs/transaction.c:2026
       flush_space+0x428/0xb64 fs/btrfs/space-info.c:921
       do_async_reclaim_data_space+0x24c/0x488 fs/btrfs/space-info.c:1437
       btrfs_async_reclaim_data_space+0x44/0x88 fs/btrfs/space-info.c:1485
       process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
       process_scheduled_works kernel/workqueue.c:3340 [inline]
       worker_thread+0x958/0xed8 kernel/workqueue.c:3421
       kthread+0x5fc/0x75c kernel/kthread.c:463
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

-> #0 (&delayed_node->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237
       lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
       __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:614
       __mutex_lock kernel/locking/mutex.c:776 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
       __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290
       btrfs_release_delayed_node fs/btrfs/delayed-inode.c:315 [inline]
       btrfs_remove_delayed_node+0x68/0x84 fs/btrfs/delayed-inode.c:1323
       btrfs_evict_inode+0x564/0xe88 fs/btrfs/inode.c:5637
       evict+0x4e0/0xa74 fs/inode.c:837
       iput_final fs/inode.c:1951 [inline]
       iput+0xc54/0xfdc fs/inode.c:2003
       iget_failed+0xec/0x134 fs/bad_inode.c:248
       btrfs_read_locked_inode+0xe1c/0x1234 fs/btrfs/inode.c:4152
       btrfs_iget+0x1b0/0x300 fs/btrfs/inode.c:5887
       btrfs_run_defrag_inode fs/btrfs/defrag.c:238 [inline]
       btrfs_run_defrag_inodes+0x520/0xdbc fs/btrfs/defrag.c:309
       cleaner_kthread+0x21c/0x418 fs/btrfs/disk-io.c:1511
       kthread+0x5fc/0x75c kernel/kthread.c:463
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(btrfs-tree-00);
                               lock(&delayed_node->mutex);
                               lock(btrfs-tree-00);
  lock(&delayed_node->mutex);

 *** DEADLOCK ***

1 lock held by btrfs-cleaner/7527:
 #0: ffff0000df5b0e18 (btrfs-tree-00){++++}-{4:4}, at: btrfs_tree_read_lock_nested+0x44/0x2ec fs/btrfs/locking.c:145

stack backtrace:
CPU: 1 UID: 0 PID: 7527 Comm: btrfs-cleaner Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2043
 check_noncircular+0x154/0x174 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237
 lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:614
 __mutex_lock kernel/locking/mutex.c:776 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
 __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290
 btrfs_release_delayed_node fs/btrfs/delayed-inode.c:315 [inline]
 btrfs_remove_delayed_node+0x68/0x84 fs/btrfs/delayed-inode.c:1323
 btrfs_evict_inode+0x564/0xe88 fs/btrfs/inode.c:5637
 evict+0x4e0/0xa74 fs/inode.c:837
 iput_final fs/inode.c:1951 [inline]
 iput+0xc54/0xfdc fs/inode.c:2003
 iget_failed+0xec/0x134 fs/bad_inode.c:248
 btrfs_read_locked_inode+0xe1c/0x1234 fs/btrfs/inode.c:4152
 btrfs_iget+0x1b0/0x300 fs/btrfs/inode.c:5887
 btrfs_run_defrag_inode fs/btrfs/defrag.c:238 [inline]
 btrfs_run_defrag_inodes+0x520/0xdbc fs/btrfs/defrag.c:309
 cleaner_kthread+0x21c/0x418 fs/btrfs/disk-io.c:1511
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844