linux-kernel - kswapd lockdep splat

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Message-ID: <543e68df-e27d-7e6e-0d50-867dd6cf2fe0@tuyoix.net>
Date: Fri, 24 Jan 2025 15:40:43 -0700 (MST)
From: Marc Aurèle La France <tsi@...oix.net>
To: Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>,
        linux-mm@...ck.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: kswapd lockdep splat

Hi.

I've yet to find anywhere to post these splats to, except to where
get_maintainer.pl suggests regarding the affected source files,
mm/vmscan.c and block/blk_mq.c.

I don't have a reproduceable case, so haven't been able to bisect
anything.

Let me know if you need more information.

Thanks and have a great day.

Marc.

--8<--

======================================================
WARNING: possible circular locking dependency detected
6.13.0 #1 Not tainted
------------------------------------------------------
kswapd0/70 is trying to acquire lock:
ffff8881025d5d78 (&q->q_usage_counter(io)){++++}-{0:0}, at: blk_mq_submit_bio+0x461/0x6e0

but task is already holding lock:
ffffffff81ef5f40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x9f/0x760

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
        lock_acquire.part.0+0x94/0x1f0
        fs_reclaim_acquire+0x8d/0xc0
        __kmalloc_node_noprof+0x86/0x360
        sbitmap_init_node+0x85/0x200
        scsi_realloc_sdev_budget_map+0xc5/0x190
        scsi_add_lun+0x3ee/0x6c0
        scsi_probe_and_add_lun+0x111/0x290
        __scsi_add_device+0xc7/0xd0
        ata_scsi_scan_host+0x93/0x1b0
        async_run_entry_fn+0x21/0xa0
        process_one_work+0x1fd/0x560
        worker_thread+0x1bd/0x3a0
        kthread+0xdc/0x110
        ret_from_fork+0x2b/0x40
        ret_from_fork_asm+0x11/0x20

-> #0 (&q->q_usage_counter(io)){++++}-{0:0}:
        check_prev_add+0xe2/0xc80
        __lock_acquire+0xf37/0x12c0
        lock_acquire.part.0+0x94/0x1f0
        bio_queue_enter+0xf1/0x220
        blk_mq_submit_bio+0x461/0x6e0
        __submit_bio+0x95/0x160
        submit_bio_noacct_nocheck+0xbd/0x1a0
        swap_writepage+0xff/0x1a0
        pageout+0xfb/0x2a0
        shrink_folio_list+0x57e/0xad0
        evict_folios+0x224/0x6e0
        try_to_shrink_lruvec+0x186/0x300
        shrink_node+0x37f/0x440
        balance_pgdat+0x2a4/0x760
        kswapd+0x1b3/0x3b0
        kthread+0xdc/0x110
        ret_from_fork+0x2b/0x40
        ret_from_fork_asm+0x11/0x20

other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(fs_reclaim);
                                lock(&q->q_usage_counter(io));
                                lock(fs_reclaim);
   rlock(&q->q_usage_counter(io));

  *** DEADLOCK ***

1 lock held by kswapd0/70:
  #0: ffffffff81ef5f40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x9f/0x760

stack backtrace:
CPU: 2 UID: 0 PID: 70 Comm: kswapd0 Not tainted 6.13.0 #1
Hardware name: ASUS All Series/Z87-WS, BIOS 2004 06/05/2014
Call Trace:
  <TASK>
  dump_stack_lvl+0x57/0x80
  print_circular_bug.cold+0x38/0x45
  check_noncircular+0x107/0x120
  ? unwind_next_frame+0x318/0x690
  check_prev_add+0xe2/0xc80
  __lock_acquire+0xf37/0x12c0
  ? stack_trace_save+0x3b/0x50
  lock_acquire.part.0+0x94/0x1f0
  ? blk_mq_submit_bio+0x461/0x6e0
  ? rcu_is_watching+0xd/0x40
  ? lock_acquire+0x100/0x140
  ? blk_mq_submit_bio+0x461/0x6e0
  ? bio_queue_enter+0xc9/0x220
  bio_queue_enter+0xf1/0x220
  ? blk_mq_submit_bio+0x461/0x6e0
  blk_mq_submit_bio+0x461/0x6e0
  ? lock_is_held_type+0xc5/0x120
  ? rcu_is_watching+0xd/0x40
  ? kmem_cache_alloc_noprof+0x209/0x260
  __submit_bio+0x95/0x160
  ? lock_is_held_type+0xc5/0x120
  ? submit_bio_noacct_nocheck+0xbd/0x1a0
  submit_bio_noacct_nocheck+0xbd/0x1a0
  swap_writepage+0xff/0x1a0
  pageout+0xfb/0x2a0
  shrink_folio_list+0x57e/0xad0
  ? rcu_is_watching+0xd/0x40
  ? scan_folios+0x5ce/0x610
  ? find_held_lock+0x2b/0x80
  ? mark_held_locks+0x40/0x70
  ? _raw_spin_unlock_irq+0x1f/0x40
  evict_folios+0x224/0x6e0
  try_to_shrink_lruvec+0x186/0x300
  shrink_node+0x37f/0x440
  balance_pgdat+0x2a4/0x760
  ? lock_acquire.part.0+0x94/0x1f0
  kswapd+0x1b3/0x3b0
  ? ipi_sync_rq_state+0x30/0x30
  ? balance_pgdat+0x760/0x760
  kthread+0xdc/0x110
  ? kthread_park+0x80/0x80
  ret_from_fork+0x2b/0x40
  ? kthread_park+0x80/0x80
  ret_from_fork_asm+0x11/0x20
  </TASK>