Kernel bug: possible deadlock in nilfs_dirty_inode (4)
Subsystem: nilfs
Status: fixed

Crash report:
======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc3-syzkaller-00013-geca631b8fe80 #0 Not tainted
------------------------------------------------------
kswapd0/73 is trying to acquire lock:
ffff888011a34610 (sb_internal#2){.+.+}-{0:0}, at: nilfs_dirty_inode+0x158/0x200 fs/nilfs2/inode.c:1110

but task is already holding lock:
ffffffff8ea37160 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
ffffffff8ea37160 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7226

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __fs_reclaim_acquire mm/page_alloc.c:3834 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3848
       might_alloc include/linux/sched/mm.h:318 [inline]
       prepare_alloc_pages+0x147/0x5b0 mm/page_alloc.c:4493
       __alloc_pages_noprof+0x16f/0x710 mm/page_alloc.c:4722
       alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
       alloc_pages_noprof mm/mempolicy.c:2345 [inline]
       folio_alloc_noprof+0x128/0x180 mm/mempolicy.c:2352
       filemap_alloc_folio_noprof+0xdf/0x500 mm/filemap.c:1010
       __filemap_get_folio+0x446/0xbd0 mm/filemap.c:1952
       block_write_begin+0x66/0x120 fs/buffer.c:2226
       nilfs_write_begin+0xa0/0x110 fs/nilfs2/inode.c:259
       page_symlink+0x2a6/0x4a0 fs/namei.c:5362
       nilfs_symlink+0x236/0x380 fs/nilfs2/namei.c:153
       vfs_symlink+0x137/0x2e0 fs/namei.c:4615
       do_symlinkat+0x222/0x3a0 fs/namei.c:4641
       __do_sys_symlink fs/namei.c:4662 [inline]
       __se_sys_symlink fs/namei.c:4660 [inline]
       __x64_sys_symlink+0x7a/0x90 fs/namei.c:4660
       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 (&nilfs->ns_segctor_sem){++++}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524
       nilfs_transaction_begin+0x320/0x6e0 fs/nilfs2/segment.c:223
       nilfs_symlink+0x135/0x380 fs/nilfs2/namei.c:140
       vfs_symlink+0x137/0x2e0 fs/namei.c:4615
       do_symlinkat+0x222/0x3a0 fs/namei.c:4641
       __do_sys_symlink fs/namei.c:4662 [inline]
       __se_sys_symlink fs/namei.c:4660 [inline]
       __x64_sys_symlink+0x7a/0x90 fs/namei.c:4660
       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 (sb_internal#2){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1716 [inline]
       sb_start_intwrite include/linux/fs.h:1899 [inline]
       nilfs_transaction_begin+0x216/0x6e0 fs/nilfs2/segment.c:220
       nilfs_dirty_inode+0x158/0x200 fs/nilfs2/inode.c:1110
       __mark_inode_dirty+0x2ee/0xe90 fs/fs-writeback.c:2493
       mark_inode_dirty_sync include/linux/fs.h:2479 [inline]
       iput+0x1f1/0xa50 fs/inode.c:1900
       __dentry_kill+0x20d/0x630 fs/dcache.c:615
       shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
       shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
       prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
       super_cache_scan+0x34f/0x4b0 fs/super.c:221
       do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
       shrink_one+0x43b/0x850 mm/vmscan.c:4818
       shrink_many mm/vmscan.c:4879 [inline]
       lru_gen_shrink_node mm/vmscan.c:4957 [inline]
       shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
       kswapd_shrink_node mm/vmscan.c:6765 [inline]
       balance_pgdat mm/vmscan.c:6957 [inline]
       kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/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#2 --> &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#2);

 *** DEADLOCK ***

2 locks held by kswapd0/73:
 #0: ffffffff8ea37160 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
 #0: ffffffff8ea37160 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7226
 #1: ffff888011a340e0 (&type->s_umount_key#44){++++}-{3:3}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff888011a340e0 (&type->s_umount_key#44){++++}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 73 Comm: kswapd0 Not tainted 6.12.0-rc3-syzkaller-00013-geca631b8fe80 #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:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1716 [inline]
 sb_start_intwrite include/linux/fs.h:1899 [inline]
 nilfs_transaction_begin+0x216/0x6e0 fs/nilfs2/segment.c:220
 nilfs_dirty_inode+0x158/0x200 fs/nilfs2/inode.c:1110
 __mark_inode_dirty+0x2ee/0xe90 fs/fs-writeback.c:2493
 mark_inode_dirty_sync include/linux/fs.h:2479 [inline]
 iput+0x1f1/0xa50 fs/inode.c:1900
 __dentry_kill+0x20d/0x630 fs/dcache.c:615
 shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
 shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
 prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
 super_cache_scan+0x34f/0x4b0 fs/super.c:221
 do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
 shrink_one+0x43b/0x850 mm/vmscan.c:4818
 shrink_many mm/vmscan.c:4879 [inline]
 lru_gen_shrink_node mm/vmscan.c:4957 [inline]
 shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
 kswapd_shrink_node mm/vmscan.c:6765 [inline]
 balance_pgdat mm/vmscan.c:6957 [inline]
 kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>