syzbot

======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-07726-g3c999d1ae3c7 #0 Not tainted
------------------------------------------------------
kswapd0/111 is trying to acquire lock:
ffff88801ff3a610 (sb_internal#4){.+.+}-{0:0}, at: nilfs_dirty_inode+0x1a4/0x270 fs/nilfs2/inode.c:1153

but task is already holding lock:
ffffffff8dd38f00 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (fs_reclaim){+.+.}-{0:0}:
       __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
       fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
       might_alloc include/linux/sched/mm.h:312 [inline]
       prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
       __alloc_pages+0x194/0x2460 mm/page_alloc.c:4564
       alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
       folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
       filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
       __filemap_get_folio+0x527/0xa90 mm/filemap.c:1926
       pagecache_get_page+0x2c/0x260 mm/folio-compat.c:93
       block_write_begin+0x38/0x4a0 fs/buffer.c:2209
       nilfs_write_begin+0x9f/0x1a0 fs/nilfs2/inode.c:262
       page_symlink+0x356/0x450 fs/namei.c:5236
       nilfs_symlink+0x23c/0x3c0 fs/nilfs2/namei.c:153
       vfs_symlink fs/namei.c:4489 [inline]
       vfs_symlink+0x3e8/0x630 fs/namei.c:4473
       do_symlinkat+0x263/0x310 fs/namei.c:4515
       __do_sys_symlinkat fs/namei.c:4531 [inline]
       __se_sys_symlinkat fs/namei.c:4528 [inline]
       __ia32_sys_symlinkat+0x97/0xc0 fs/namei.c:4528
       do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
       __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
       do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
       entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #1 (&nilfs->ns_segctor_sem){++++}-{3:3}:
       down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
       nilfs_transaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
       nilfs_create+0xb7/0x320 fs/nilfs2/namei.c:82
       lookup_open.isra.0+0x10a1/0x13c0 fs/namei.c:3505
       open_last_lookups fs/namei.c:3574 [inline]
       path_openat+0x92f/0x2990 fs/namei.c:3804
       do_filp_open+0x1dc/0x430 fs/namei.c:3834
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
       do_sys_open fs/open.c:1421 [inline]
       __do_compat_sys_openat fs/open.c:1481 [inline]
       __se_compat_sys_openat fs/open.c:1479 [inline]
       __ia32_compat_sys_openat+0x16e/0x210 fs/open.c:1479
       do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
       __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
       do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
       entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #0 (sb_internal#4){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1661 [inline]
       sb_start_intwrite include/linux/fs.h:1844 [inline]
       nilfs_transaction_begin+0x21b/0xa40 fs/nilfs2/segment.c:220
       nilfs_dirty_inode+0x1a4/0x270 fs/nilfs2/inode.c:1153
       __mark_inode_dirty+0x1f0/0xe70 fs/fs-writeback.c:2486
       mark_inode_dirty_sync include/linux/fs.h:2426 [inline]
       iput.part.0+0x5b/0x7f0 fs/inode.c:1764
       iput+0x5c/0x80 fs/inode.c:1757
       dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
       __dentry_kill+0x1d0/0x600 fs/dcache.c:603
       shrink_kill fs/dcache.c:1048 [inline]
       shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
       prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
       super_cache_scan+0x32a/0x550 fs/super.c:221
       do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
       shrink_slab_memcg mm/shrinker.c:548 [inline]
       shrink_slab+0xa87/0x1310 mm/shrinker.c:626
       shrink_one+0x493/0x7c0 mm/vmscan.c:4774
       shrink_many mm/vmscan.c:4835 [inline]
       lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
       shrink_node mm/vmscan.c:5894 [inline]
       kswapd_shrink_node mm/vmscan.c:6704 [inline]
       balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
       kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Chain exists of:
  sb_internal#4 --> &nilfs->ns_segctor_sem --> fs_reclaim

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&nilfs->ns_segctor_sem);
                               lock(fs_reclaim);
  rlock(sb_internal#4);

 *** DEADLOCK ***

2 locks held by kswapd0/111:
 #0: ffffffff8dd38f00 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782
 #1: ffff88801ff3a0e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_trylock_shared fs/super.c:561 [inline]
 #1: ffff88801ff3a0e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_cache_scan+0x96/0x550 fs/super.c:196

stack backtrace:
CPU: 3 PID: 111 Comm: kswapd0 Not tainted 6.9.0-syzkaller-07726-g3c999d1ae3c7 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1661 [inline]
 sb_start_intwrite include/linux/fs.h:1844 [inline]
 nilfs_transaction_begin+0x21b/0xa40 fs/nilfs2/segment.c:220
 nilfs_dirty_inode+0x1a4/0x270 fs/nilfs2/inode.c:1153
 __mark_inode_dirty+0x1f0/0xe70 fs/fs-writeback.c:2486
 mark_inode_dirty_sync include/linux/fs.h:2426 [inline]
 iput.part.0+0x5b/0x7f0 fs/inode.c:1764
 iput+0x5c/0x80 fs/inode.c:1757
 dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
 __dentry_kill+0x1d0/0x600 fs/dcache.c:603
 shrink_kill fs/dcache.c:1048 [inline]
 shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
 prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
 super_cache_scan+0x32a/0x550 fs/super.c:221
 do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
 shrink_slab_memcg mm/shrinker.c:548 [inline]
 shrink_slab+0xa87/0x1310 mm/shrinker.c:626
 shrink_one+0x493/0x7c0 mm/vmscan.c:4774
 shrink_many mm/vmscan.c:4835 [inline]
 lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
 shrink_node mm/vmscan.c:5894 [inline]
 kswapd_shrink_node mm/vmscan.c:6704 [inline]
 balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
 kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>