====================================================== WARNING: possible circular locking dependency detected 5.5.0-syzkaller #0 Not tainted ------------------------------------------------------ kswapd0/1868 is trying to acquire lock: ffff8880a8d22248 (&sb->s_type->i_mutex_key#12){+.+.}, at: inode_lock include/linux/fs.h:791 [inline] ffff8880a8d22248 (&sb->s_type->i_mutex_key#12){+.+.}, at: shmem_fallocate+0xe8/0xe30 mm/shmem.c:2736 but task is already holding lock: ffffffff89107e90 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x4/0x30 mm/page_alloc.c:4072 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+0x24/0x30 mm/page_alloc.c:4073 fs_reclaim_acquire mm/page_alloc.c:4084 [inline] prepare_alloc_pages+0x21c/0x460 mm/page_alloc.c:4667 __alloc_pages_nodemask+0xb2/0x5d0 mm/page_alloc.c:4719 alloc_pages_vma+0x4f3/0xd40 mm/mempolicy.c:2174 shmem_alloc_page mm/shmem.c:1499 [inline] shmem_alloc_and_acct_page+0x425/0xbb0 mm/shmem.c:1524 shmem_getpage_gfp+0x2814/0x2f80 mm/shmem.c:1838 shmem_getpage mm/shmem.c:154 [inline] shmem_write_begin+0xcb/0x1b0 mm/shmem.c:2488 generic_perform_write+0x23d/0x4f0 mm/filemap.c:3309 __generic_file_write_iter+0x235/0x500 mm/filemap.c:3438 generic_file_write_iter+0x4b1/0x660 mm/filemap.c:3470 call_write_iter include/linux/fs.h:1902 [inline] new_sync_write fs/read_write.c:483 [inline] __vfs_write+0x5a1/0x740 fs/read_write.c:496 vfs_write+0x270/0x580 fs/read_write.c:558 ksys_write+0x117/0x220 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+0x7b/0x90 fs/read_write.c:620 do_syscall_64+0xf7/0x1c0 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+0x57/0x140 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0xe8/0xe30 mm/shmem.c:2736 ashmem_shrink_scan+0x383/0x4a0 drivers/staging/android/ashmem.c:462 do_shrink_slab+0x397/0x5d0 mm/vmscan.c:526 shrink_slab+0x16d/0x290 mm/vmscan.c:687 shrink_node_memcgs+0x2af/0x5b0 mm/vmscan.c:2687 shrink_node+0xb6b/0x1970 mm/vmscan.c:2791 kswapd_shrink_node mm/vmscan.c:3539 [inline] balance_pgdat+0xb12/0x1620 mm/vmscan.c:3697 kswapd+0x2e4/0x530 mm/vmscan.c:3948 kthread+0x332/0x350 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 kswapd0/1868: #0: ffffffff89107e90 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x4/0x30 mm/page_alloc.c:4072 #1: ffffffff89100388 (shrinker_rwsem){++++}, at: shrink_slab+0x93/0x290 mm/vmscan.c:677 stack backtrace: CPU: 1 PID: 1868 Comm: kswapd0 Not tainted 5.5.0-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+0x1fb/0x318 lib/dump_stack.c:118 print_circular_bug+0xc3f/0xe70 kernel/locking/lockdep.c:1684 check_noncircular+0x206/0x3a0 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+0x57/0x140 kernel/locking/rwsem.c:1534 inode_lock include/linux/fs.h:791 [inline] shmem_fallocate+0xe8/0xe30 mm/shmem.c:2736 ashmem_shrink_scan+0x383/0x4a0 drivers/staging/android/ashmem.c:462 do_shrink_slab+0x397/0x5d0 mm/vmscan.c:526 shrink_slab+0x16d/0x290 mm/vmscan.c:687 shrink_node_memcgs+0x2af/0x5b0 mm/vmscan.c:2687 shrink_node+0xb6b/0x1970 mm/vmscan.c:2791 kswapd_shrink_node mm/vmscan.c:3539 [inline] balance_pgdat+0xb12/0x1620 mm/vmscan.c:3697 kswapd+0x2e4/0x530 mm/vmscan.c:3948 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352