====================================================== WARNING: possible circular locking dependency detected 5.5.0-rc3-syzkaller #0 Not tainted ------------------------------------------------------ kswapd0/1852 is trying to acquire lock: ffff888098919cd8 (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock include/linux/fs.h:791 [inline] ffff888098919cd8 (&sb->s_type->i_mutex_key#13){+.+.}, at: shmem_fallocate+0x15a/0xd40 mm/shmem.c:2735 but task is already holding lock: ffffffff89a41e00 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:4922 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}: __fs_reclaim_acquire mm/page_alloc.c:4084 [inline] fs_reclaim_acquire.part.0+0x24/0x30 mm/page_alloc.c:4095 fs_reclaim_acquire mm/page_alloc.c:4695 [inline] prepare_alloc_pages mm/page_alloc.c:4692 [inline] __alloc_pages_nodemask+0x52d/0x910 mm/page_alloc.c:4744 alloc_pages_vma+0xdd/0x620 mm/mempolicy.c:2170 shmem_alloc_page+0xc0/0x180 mm/shmem.c:1499 shmem_alloc_and_acct_page+0x165/0x990 mm/shmem.c:1524 shmem_getpage_gfp+0x56d/0x29a0 mm/shmem.c:1838 shmem_getpage mm/shmem.c:154 [inline] shmem_write_begin+0x105/0x1e0 mm/shmem.c:2487 generic_perform_write+0x23b/0x540 mm/filemap.c:3309 __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3438 generic_file_write_iter+0x420/0x68e mm/filemap.c:3470 call_write_iter include/linux/fs.h:1902 [inline] new_sync_write+0x4d3/0x770 fs/read_write.c:483 __vfs_write+0xe1/0x110 fs/read_write.c:496 vfs_write+0x268/0x5d0 fs/read_write.c:558 ksys_write+0x14f/0x290 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:620 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sb->s_type->i_mutex_key#13){+.+.}: check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 down_write+0x93/0x150 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0x15a/0xd40 mm/shmem.c:2735 ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline] ashmem_shrink_scan+0x370/0x510 drivers/staging/android/ashmem.c:437 do_shrink_slab+0x40f/0xad0 mm/vmscan.c:526 shrink_slab mm/vmscan.c:687 [inline] shrink_slab+0x19a/0x680 mm/vmscan.c:660 shrink_node_memcgs mm/vmscan.c:2687 [inline] shrink_node+0x46a/0x1ad0 mm/vmscan.c:2791 kswapd_shrink_node mm/vmscan.c:3539 [inline] balance_pgdat+0x7c8/0x11f0 mm/vmscan.c:3697 kswapd+0x5c3/0xf30 mm/vmscan.c:3948 kthread+0x361/0x430 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#13); lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#13); *** DEADLOCK *** 2 locks held by kswapd0/1852: #0: ffffffff89a41e00 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:4922 #1: ffffffff89a1f948 (shrinker_rwsem){++++}, at: shrink_slab mm/vmscan.c:677 [inline] #1: ffffffff89a1f948 (shrinker_rwsem){++++}, at: shrink_slab+0xe6/0x680 mm/vmscan.c:660 stack backtrace: CPU: 0 PID: 1852 Comm: kswapd0 Not tainted 5.5.0-rc3-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+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1685 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809 check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 down_write+0x93/0x150 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0x15a/0xd40 mm/shmem.c:2735 ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline] ashmem_shrink_scan+0x370/0x510 drivers/staging/android/ashmem.c:437 do_shrink_slab+0x40f/0xad0 mm/vmscan.c:526 shrink_slab mm/vmscan.c:687 [inline] shrink_slab+0x19a/0x680 mm/vmscan.c:660 shrink_node_memcgs mm/vmscan.c:2687 [inline] shrink_node+0x46a/0x1ad0 mm/vmscan.c:2791 kswapd_shrink_node mm/vmscan.c:3539 [inline] balance_pgdat+0x7c8/0x11f0 mm/vmscan.c:3697 kswapd+0x5c3/0xf30 mm/vmscan.c:3948 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352