====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc4-syzkaller #0 Not tainted ------------------------------------------------------ kswapd0/1875 is trying to acquire lock: ffff888046417790 (&sb->s_type->i_mutex_key#12){+.+.}, at: inode_lock include/linux/fs.h:791 [inline] ffff888046417790 (&sb->s_type->i_mutex_key#12){+.+.}, at: shmem_fallocate+0xef/0xdb0 mm/shmem.c:2736 but task is already holding lock: ffffffff89107c80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:3728 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __fs_reclaim_acquire+0x20/0x30 mm/page_alloc.c:4073 fs_reclaim_acquire mm/page_alloc.c:4084 [inline] prepare_alloc_pages+0x21d/0x4a0 mm/page_alloc.c:4667 __alloc_pages_nodemask+0xbf/0x600 mm/page_alloc.c:4719 alloc_pages_vma+0x4dd/0xd10 mm/mempolicy.c:2174 shmem_alloc_page mm/shmem.c:1499 [inline] shmem_alloc_and_acct_page+0x40e/0xbe0 mm/shmem.c:1524 shmem_getpage_gfp+0x21b7/0x2db0 mm/shmem.c:1838 shmem_getpage mm/shmem.c:154 [inline] shmem_write_begin+0xcd/0x1a0 mm/shmem.c:2488 generic_perform_write+0x23b/0x4e0 mm/filemap.c:3287 __generic_file_write_iter+0x22b/0x4e0 mm/filemap.c:3416 generic_file_write_iter+0x4a6/0x650 mm/filemap.c:3448 call_write_iter include/linux/fs.h:1901 [inline] new_sync_write fs/read_write.c:483 [inline] __vfs_write+0x549/0x710 fs/read_write.c:496 vfs_write+0x271/0x570 fs/read_write.c:558 ksys_write+0x115/0x220 fs/read_write.c:611 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sb->s_type->i_mutex_key#12){+.+.}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_write+0x55/0x130 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0xef/0xdb0 mm/shmem.c:2736 ashmem_shrink_scan+0x367/0x4a0 drivers/staging/android/ashmem.c:490 do_shrink_slab+0x36f/0x5c0 mm/vmscan.c:512 shrink_slab+0x188/0x2b0 mm/vmscan.c:673 shrink_node_memcgs+0x414/0x5e0 mm/vmscan.c:2676 shrink_node+0xb66/0x19c0 mm/vmscan.c:2780 kswapd_shrink_node mm/vmscan.c:3526 [inline] balance_pgdat+0xb12/0x1620 mm/vmscan.c:3684 kswapd+0x2f7/0x540 mm/vmscan.c:3935 kthread+0x317/0x340 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#12); lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#12); *** DEADLOCK *** 2 locks held by kswapd0/1875: #0: ffffffff89107c80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:3728 #1: ffffffff89100168 (shrinker_rwsem){++++}, at: shrink_slab+0xa8/0x2b0 mm/vmscan.c:663 stack backtrace: CPU: 1 PID: 1875 Comm: kswapd0 Not tainted 5.6.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1e9/0x30e lib/dump_stack.c:118 print_circular_bug+0xc3f/0xe70 kernel/locking/lockdep.c:1684 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_write+0x55/0x130 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0xef/0xdb0 mm/shmem.c:2736 ashmem_shrink_scan+0x367/0x4a0 drivers/staging/android/ashmem.c:490 do_shrink_slab+0x36f/0x5c0 mm/vmscan.c:512 shrink_slab+0x188/0x2b0 mm/vmscan.c:673 shrink_node_memcgs+0x414/0x5e0 mm/vmscan.c:2676 shrink_node+0xb66/0x19c0 mm/vmscan.c:2780 kswapd_shrink_node mm/vmscan.c:3526 [inline] balance_pgdat+0xb12/0x1620 mm/vmscan.c:3684 kswapd+0x2f7/0x540 mm/vmscan.c:3935 kthread+0x317/0x340 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352