syzbot

======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc7-syzkaller-00102-gce69b4019001 #0 Not tainted
------------------------------------------------------
kswapd0/88 is trying to acquire lock:
ffffe8ffffc20c10 (&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex){+.+.}-{4:4}, at: acomp_ctx_get_cpu_lock mm/zswap.c:899 [inline]
ffffe8ffffc20c10 (&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex){+.+.}-{4:4}, at: zswap_compress mm/zswap.c:931 [inline]
ffffe8ffffc20c10 (&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex){+.+.}-{4:4}, at: zswap_store_page mm/zswap.c:1456 [inline]
ffffe8ffffc20c10 (&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex){+.+.}-{4:4}, at: zswap_store+0xa3b/0x1c30 mm/zswap.c:1563

but task is already holding lock:
ffffffff8ea36ec0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6874 [inline]
ffffffff8ea36ec0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x36f0 mm/vmscan.c:7256

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __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:4070 [inline]
       slab_alloc_node mm/slub.c:4148 [inline]
       __kmalloc_cache_node_noprof+0x40/0x3a0 mm/slub.c:4337
       kmalloc_node_noprof include/linux/slab.h:924 [inline]
       zswap_cpu_comp_prepare+0xdc/0x400 mm/zswap.c:828
       cpuhp_invoke_callback+0x415/0x830 kernel/cpu.c:204
       cpuhp_issue_call+0x46f/0x7e0
       __cpuhp_state_add_instance_cpuslocked+0x1ed/0x500 kernel/cpu.c:2437
       __cpuhp_state_add_instance+0x27/0x40 kernel/cpu.c:2458
       cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
       zswap_pool_create+0x38c/0x680 mm/zswap.c:291
       zswap_setup+0x32a/0x4b0 mm/zswap.c:1811
       do_one_initcall+0x248/0x870 init/main.c:1266
       do_initcall_level+0x157/0x210 init/main.c:1328
       do_initcalls+0x3f/0x80 init/main.c:1344
       kernel_init_freeable+0x435/0x5d0 init/main.c:1577
       kernel_init+0x1d/0x2b0 init/main.c:1466
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex){+.+.}-{4:4}:
       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+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       acomp_ctx_get_cpu_lock mm/zswap.c:899 [inline]
       zswap_compress mm/zswap.c:931 [inline]
       zswap_store_page mm/zswap.c:1456 [inline]
       zswap_store+0xa3b/0x1c30 mm/zswap.c:1563
       swap_writepage+0x647/0xce0 mm/page_io.c:279
       shmem_writepage+0x1248/0x1610 mm/shmem.c:1579
       pageout mm/vmscan.c:696 [inline]
       shrink_folio_list+0x3b68/0x5ca0 mm/vmscan.c:1374
       evict_folios+0x3c92/0x58c0 mm/vmscan.c:4600
       try_to_shrink_lruvec+0x9a6/0xc70 mm/vmscan.c:4799
       shrink_one+0x3b9/0x850 mm/vmscan.c:4844
       shrink_many mm/vmscan.c:4907 [inline]
       lru_gen_shrink_node mm/vmscan.c:4985 [inline]
       shrink_node+0x37c5/0x3e50 mm/vmscan.c:5966
       kswapd_shrink_node mm/vmscan.c:6795 [inline]
       balance_pgdat mm/vmscan.c:6987 [inline]
       kswapd+0x1ca9/0x36f0 mm/vmscan.c:7256
       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:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex);
                               lock(fs_reclaim);
  lock(&per_cpu_ptr(pool->acomp_ctx, cpu)->mutex);

 *** DEADLOCK ***

1 lock held by kswapd0/88:
 #0: ffffffff8ea36ec0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6874 [inline]
 #0: ffffffff8ea36ec0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x36f0 mm/vmscan.c:7256

stack backtrace:
CPU: 0 UID: 0 PID: 88 Comm: kswapd0 Not tainted 6.13.0-rc7-syzkaller-00102-gce69b4019001 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
 acomp_ctx_get_cpu_lock mm/zswap.c:899 [inline]
 zswap_compress mm/zswap.c:931 [inline]
 zswap_store_page mm/zswap.c:1456 [inline]
 zswap_store+0xa3b/0x1c30 mm/zswap.c:1563
 swap_writepage+0x647/0xce0 mm/page_io.c:279
 shmem_writepage+0x1248/0x1610 mm/shmem.c:1579
 pageout mm/vmscan.c:696 [inline]
 shrink_folio_list+0x3b68/0x5ca0 mm/vmscan.c:1374
 evict_folios+0x3c92/0x58c0 mm/vmscan.c:4600
 try_to_shrink_lruvec+0x9a6/0xc70 mm/vmscan.c:4799
 shrink_one+0x3b9/0x850 mm/vmscan.c:4844
 shrink_many mm/vmscan.c:4907 [inline]
 lru_gen_shrink_node mm/vmscan.c:4985 [inline]
 shrink_node+0x37c5/0x3e50 mm/vmscan.c:5966
 kswapd_shrink_node mm/vmscan.c:6795 [inline]
 balance_pgdat mm/vmscan.c:6987 [inline]
 kswapd+0x1ca9/0x36f0 mm/vmscan.c:7256
 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>