syzbot

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc4-syzkaller-00248-g03d38806a902 #0 Not tainted
------------------------------------------------------
kswapd0/79 is trying to acquire lock:
ffff8880131f00c0 (&bmap->b_sem){++++}-{4:4}, at: nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305

but task is already holding lock:
ffffffff8ec3a240 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
ffffffff8ec3a240 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3867
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4066 [inline]
       slab_alloc_node mm/slub.c:4144 [inline]
       kmem_cache_alloc_node_noprof+0x48/0x380 mm/slub.c:4216
       __alloc_skb+0x1c3/0x440 net/core/skbuff.c:596
       alloc_skb include/linux/skbuff.h:1331 [inline]
       alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289
       uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
       kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207
       bus_uevent_store+0x116/0x170 drivers/base/bus.c:832
       kernfs_fop_write_iter+0x3a0/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0xacf/0xd10 fs/read_write.c:679
       ksys_write+0x18f/0x2b0 fs/read_write.c:731
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (uevent_sock_mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
       kobject_uevent_net_broadcast+0x280/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       loop_set_size drivers/block/loop.c:235 [inline]
       loop_set_status+0x4f8/0x800 drivers/block/loop.c:1292
       lo_ioctl+0xce6/0x2870
       blkdev_ioctl+0x5d0/0x6f0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       bio_queue_enter block/blk.h:78 [inline]
       blk_mq_submit_bio+0x14e1/0x25d0 block/blk-mq.c:3091
       __submit_bio+0x2cf/0x6a0 block/blk-core.c:628
       __submit_bio_noacct_mq block/blk-core.c:715 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:744
       nilfs_mdt_submit_block+0x5c5/0x880 fs/nilfs2/mdt.c:153
       nilfs_mdt_read_block+0xeb/0x430 fs/nilfs2/mdt.c:178
       nilfs_mdt_get_block+0x10a/0xa30 fs/nilfs2/mdt.c:254
       nilfs_palloc_get_block+0x181/0x2a0 fs/nilfs2/alloc.c:239
       nilfs_palloc_get_desc_block fs/nilfs2/alloc.c:296 [inline]
       nilfs_palloc_prepare_alloc_entry+0x3ee/0x1070 fs/nilfs2/alloc.c:607
       nilfs_dat_prepare_alloc+0x27/0x110 fs/nilfs2/dat.c:78
       nilfs_bmap_prepare_alloc_ptr fs/nilfs2/bmap.h:195 [inline]
       nilfs_direct_insert+0x1bd/0x510 fs/nilfs2/direct.c:127
       nilfs_bmap_do_insert fs/nilfs2/bmap.c:126 [inline]
       nilfs_bmap_insert+0x25e/0x3c0 fs/nilfs2/bmap.c:149
       nilfs_get_block+0x428/0x8e0 fs/nilfs2/inode.c:100
       __block_write_begin_int+0x692/0x19a0 fs/buffer.c:2116
       nilfs_prepare_chunk fs/nilfs2/dir.c:86 [inline]
       nilfs_make_empty+0xf6/0x4d0 fs/nilfs2/dir.c:578
       nilfs_mkdir+0x1cc/0x340 fs/nilfs2/namei.c:245
       vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4313
       do_mkdirat+0x264/0x3a0 fs/namei.c:4336
       __do_sys_mkdirat fs/namei.c:4351 [inline]
       __se_sys_mkdirat fs/namei.c:4349 [inline]
       __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4349
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&bmap->b_sem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       down_write+0x99/0x220 kernel/locking/rwsem.c:1577
       nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305
       nilfs_clear_inode+0x147/0x2a0 fs/nilfs2/inode.c:836
       nilfs_evict_inode+0x105/0x500 fs/nilfs2/inode.c:856
       evict+0x4e8/0x9a0 fs/inode.c:796
       dispose_list fs/inode.c:845 [inline]
       prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
       super_cache_scan+0x38c/0x4b0 fs/super.c:223
       do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
       shrink_slab_memcg mm/shrinker.c:550 [inline]
       shrink_slab+0x878/0x14d0 mm/shrinker.c:628
       shrink_one+0x43b/0x850 mm/vmscan.c:4868
       shrink_many mm/vmscan.c:4929 [inline]
       lru_gen_shrink_node mm/vmscan.c:5007 [inline]
       shrink_node+0x379b/0x3e20 mm/vmscan.c:5978
       kswapd_shrink_node mm/vmscan.c:6807 [inline]
       balance_pgdat mm/vmscan.c:6999 [inline]
       kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
       kthread+0x7a9/0x920 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Chain exists of:
  &bmap->b_sem --> uevent_sock_mutex --> fs_reclaim

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(uevent_sock_mutex);
                               lock(fs_reclaim);
  lock(&bmap->b_sem);

 *** DEADLOCK ***

2 locks held by kswapd0/79:
 #0: ffffffff8ec3a240 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
 #0: ffffffff8ec3a240 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264
 #1: ffff8880350220e0 (&type->s_umount_key#49){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff8880350220e0 (&type->s_umount_key#49){.+.+}-{4:4}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 79 Comm: kswapd0 Not tainted 6.14.0-rc4-syzkaller-00248-g03d38806a902 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2076
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 down_write+0x99/0x220 kernel/locking/rwsem.c:1577
 nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305
 nilfs_clear_inode+0x147/0x2a0 fs/nilfs2/inode.c:836
 nilfs_evict_inode+0x105/0x500 fs/nilfs2/inode.c:856
 evict+0x4e8/0x9a0 fs/inode.c:796
 dispose_list fs/inode.c:845 [inline]
 prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
 super_cache_scan+0x38c/0x4b0 fs/super.c:223
 do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0x878/0x14d0 mm/shrinker.c:628
 shrink_one+0x43b/0x850 mm/vmscan.c:4868
 shrink_many mm/vmscan.c:4929 [inline]
 lru_gen_shrink_node mm/vmscan.c:5007 [inline]
 shrink_node+0x379b/0x3e20 mm/vmscan.c:5978
 kswapd_shrink_node mm/vmscan.c:6807 [inline]
 balance_pgdat mm/vmscan.c:6999 [inline]
 kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>