syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/78 is trying to acquire lock:
ffff888040daae18 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_reclaim_inode fs/xfs/xfs_icache.c:1040 [inline]
ffff888040daae18 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1732 [inline]
ffff888040daae18 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_icwalk_ag+0x12c5/0x1ab0 fs/xfs/xfs_icache.c:1814

but task is already holding lock:
ffffffff8e047ae0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline]
ffffffff8e047ae0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __fs_reclaim_acquire mm/page_alloc.c:4264 [inline]
       fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4278
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4929 [inline]
       slab_alloc_node mm/slub.c:5264 [inline]
       __kmalloc_cache_noprof+0x40/0x6f0 mm/slub.c:5766
       kmalloc_noprof include/linux/slab.h:957 [inline]
       iomap_fill_dirty_folios+0xf4/0x260 fs/iomap/buffered-io.c:1557
       xfs_buffered_write_iomap_begin+0xa23/0x1a70 fs/xfs/xfs_iomap.c:1857
       iomap_iter+0x5f2/0xf10 fs/iomap/iter.c:110
       iomap_zero_range+0x1cc/0xa50 fs/iomap/buffered-io.c:1590
       xfs_zero_range+0x9a/0x100 fs/xfs/xfs_iomap.c:2289
       xfs_setattr_size+0x4b4/0xee0 fs/xfs/xfs_iops.c:993
       __xfs_file_fallocate+0x10e1/0x1610 include/linux/fs.h:-1
       xfs_file_fallocate+0x27b/0x340 fs/xfs/xfs_file.c:1462
       vfs_fallocate+0x669/0x7e0 fs/open.c:342
       ksys_fallocate fs/open.c:366 [inline]
       __do_sys_fallocate fs/open.c:371 [inline]
       __se_sys_fallocate fs/open.c:369 [inline]
       __x64_sys_fallocate+0xc0/0x110 fs/open.c:369
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&xfs_nondir_ilock_class){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       down_write_nested+0x9d/0x200 kernel/locking/rwsem.c:1706
       xfs_reclaim_inode fs/xfs/xfs_icache.c:1040 [inline]
       xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1732 [inline]
       xfs_icwalk_ag+0x12c5/0x1ab0 fs/xfs/xfs_icache.c:1814
       xfs_icwalk fs/xfs/xfs_icache.c:1862 [inline]
       xfs_reclaim_inodes_nr+0x1e3/0x260 fs/xfs/xfs_icache.c:1106
       super_cache_scan+0x41b/0x4b0 fs/super.c:228
       do_shrink_slab+0x6ef/0x1110 mm/shrinker.c:437
       shrink_slab+0xd74/0x10d0 mm/shrinker.c:664
       shrink_one+0x28a/0x7c0 mm/vmscan.c:4955
       shrink_many mm/vmscan.c:5016 [inline]
       lru_gen_shrink_node mm/vmscan.c:5094 [inline]
       shrink_node+0x315d/0x3780 mm/vmscan.c:6081
       kswapd_shrink_node mm/vmscan.c:6941 [inline]
       balance_pgdat mm/vmscan.c:7124 [inline]
       kswapd+0x147c/0x2800 mm/vmscan.c:7389
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&xfs_nondir_ilock_class);
                               lock(fs_reclaim);
  lock(&xfs_nondir_ilock_class);

 *** DEADLOCK ***

2 locks held by kswapd0/78:
 #0: ffffffff8e047ae0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline]
 #0: ffffffff8e047ae0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389
 #1: ffff8880117220e0 (&type->s_umount_key#54){++++}-{4:4}, at: super_trylock_shared fs/super.c:563 [inline]
 #1: ffff8880117220e0 (&type->s_umount_key#54){++++}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197

stack backtrace:
CPU: 0 UID: 0 PID: 78 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) 
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_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 down_write_nested+0x9d/0x200 kernel/locking/rwsem.c:1706
 xfs_reclaim_inode fs/xfs/xfs_icache.c:1040 [inline]
 xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1732 [inline]
 xfs_icwalk_ag+0x12c5/0x1ab0 fs/xfs/xfs_icache.c:1814
 xfs_icwalk fs/xfs/xfs_icache.c:1862 [inline]
 xfs_reclaim_inodes_nr+0x1e3/0x260 fs/xfs/xfs_icache.c:1106
 super_cache_scan+0x41b/0x4b0 fs/super.c:228
 do_shrink_slab+0x6ef/0x1110 mm/shrinker.c:437
 shrink_slab+0xd74/0x10d0 mm/shrinker.c:664
 shrink_one+0x28a/0x7c0 mm/vmscan.c:4955
 shrink_many mm/vmscan.c:5016 [inline]
 lru_gen_shrink_node mm/vmscan.c:5094 [inline]
 shrink_node+0x315d/0x3780 mm/vmscan.c:6081
 kswapd_shrink_node mm/vmscan.c:6941 [inline]
 balance_pgdat mm/vmscan.c:7124 [inline]
 kswapd+0x147c/0x2800 mm/vmscan.c:7389
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>