====================================================== WARNING: possible circular locking dependency detected 5.6.0-next-20200408-syzkaller #0 Not tainted ------------------------------------------------------ kswapd0/1876 is trying to acquire lock: ffff8880a696cff0 (&sb->s_type->i_mutex_key#16){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:797 [inline] ffff8880a696cff0 (&sb->s_type->i_mutex_key#16){+.+.}-{3:3}, at: shmem_fallocate+0x153/0xd40 mm/shmem.c:2731 but task is already holding lock: ffffffff89a63900 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:4981 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4155 [inline] fs_reclaim_acquire.part.0+0x20/0x30 mm/page_alloc.c:4166 fs_reclaim_acquire mm/page_alloc.c:4755 [inline] prepare_alloc_pages mm/page_alloc.c:4752 [inline] __alloc_pages_nodemask+0x4da/0x810 mm/page_alloc.c:4804 alloc_pages_vma+0xd9/0x600 mm/mempolicy.c:2255 shmem_alloc_page+0xb0/0x170 mm/shmem.c:1486 shmem_alloc_and_acct_page+0x160/0x980 mm/shmem.c:1511 shmem_getpage_gfp+0x502/0x2a10 mm/shmem.c:1828 shmem_getpage mm/shmem.c:154 [inline] shmem_write_begin+0x102/0x1e0 mm/shmem.c:2483 generic_perform_write+0x20a/0x4e0 mm/filemap.c:3308 __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3437 generic_file_write_iter+0x3f3/0x630 mm/filemap.c:3469 call_write_iter include/linux/fs.h:1907 [inline] new_sync_write+0x4a2/0x700 fs/read_write.c:484 __vfs_write+0xc9/0x100 fs/read_write.c:497 vfs_write+0x268/0x5d0 fs/read_write.c:559 ksys_write+0x12d/0x250 fs/read_write.c:612 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 -> #0 (&sb->s_type->i_mutex_key#16){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x2c21/0x4e00 kernel/locking/lockdep.c:4344 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 inode_lock include/linux/fs.h:797 [inline] shmem_fallocate+0x153/0xd40 mm/shmem.c:2731 ashmem_shrink_scan drivers/staging/android/ashmem.c:490 [inline] ashmem_shrink_scan+0x34d/0x500 drivers/staging/android/ashmem.c:465 do_shrink_slab+0x3fa/0xa30 mm/vmscan.c:512 shrink_slab mm/vmscan.c:673 [inline] shrink_slab+0x16f/0x5f0 mm/vmscan.c:646 shrink_node_memcgs mm/vmscan.c:2673 [inline] shrink_node+0x477/0x1b20 mm/vmscan.c:2777 kswapd_shrink_node mm/vmscan.c:3523 [inline] balance_pgdat+0x76c/0x1130 mm/vmscan.c:3681 kswapd+0x5d0/0xe80 mm/vmscan.c:3935 kthread+0x388/0x470 kernel/kthread.c:268 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#16); lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#16); *** DEADLOCK *** 2 locks held by kswapd0/1876: #0: ffffffff89a63900 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x0/0x30 mm/page_alloc.c:4981 #1: ffffffff89a3e250 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab mm/vmscan.c:663 [inline] #1: ffffffff89a3e250 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0xc7/0x5f0 mm/vmscan.c:646 stack backtrace: CPU: 1 PID: 1876 Comm: kswapd0 Not tainted 5.6.0-next-20200408-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+0x188/0x20d lib/dump_stack.c:118 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1846 check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x2c21/0x4e00 kernel/locking/lockdep.c:4344 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 inode_lock include/linux/fs.h:797 [inline] shmem_fallocate+0x153/0xd40 mm/shmem.c:2731 ashmem_shrink_scan drivers/staging/android/ashmem.c:490 [inline] ashmem_shrink_scan+0x34d/0x500 drivers/staging/android/ashmem.c:465 do_shrink_slab+0x3fa/0xa30 mm/vmscan.c:512 shrink_slab mm/vmscan.c:673 [inline] shrink_slab+0x16f/0x5f0 mm/vmscan.c:646 shrink_node_memcgs mm/vmscan.c:2673 [inline] shrink_node+0x477/0x1b20 mm/vmscan.c:2777 kswapd_shrink_node mm/vmscan.c:3523 [inline] balance_pgdat+0x76c/0x1130 mm/vmscan.c:3681 kswapd+0x5d0/0xe80 mm/vmscan.c:3935 kthread+0x388/0x470 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352