> syzbot found the following crash on Mon, 09 Sep 2019 20:38:05 -0700 > > HEAD commit: 6d028043 Add linux-next specific files for 20190830 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=12359ec6600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=82a6bec43ab0cb69 > dashboard link: https://syzkaller.appspot.com/bug?extid=5d04068d02b9da8a0947 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+5d04068d02b9da8a0947@xxxxxxxxxxxxxxxxxxxxxxxxx > > ====================================================== > WARNING: possible circular locking dependency detected > 5.3.0-rc6-next-20190830 #75 Not tainted > ------------------------------------------------------ > kswapd0/1770 is trying to acquire lock: > ffff8880a0b9b780 (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock > include/linux/fs.h:789 [inline] > ffff8880a0b9b780 (&sb->s_type->i_mutex_key#13){+.+.}, at: > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 > > but task is already holding lock: > ffffffff89042f80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 > mm/page_alloc.c:4889 > > 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:4075 [inline] > fs_reclaim_acquire.part.0+0x24/0x30 mm/page_alloc.c:4086 > fs_reclaim_acquire mm/page_alloc.c:4662 [inline] > prepare_alloc_pages mm/page_alloc.c:4659 [inline] > __alloc_pages_nodemask+0x52f/0x900 mm/page_alloc.c:4711 > alloc_pages_vma+0x1bc/0x3f0 mm/mempolicy.c:2114 > shmem_alloc_page+0xbd/0x180 mm/shmem.c:1496 > shmem_alloc_and_acct_page+0x165/0x990 mm/shmem.c:1521 > shmem_getpage_gfp+0x598/0x2680 mm/shmem.c:1835 > shmem_getpage mm/shmem.c:152 [inline] > shmem_write_begin+0x105/0x1e0 mm/shmem.c:2480 > generic_perform_write+0x23b/0x540 mm/filemap.c:3304 > __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3433 > generic_file_write_iter+0x420/0x690 mm/filemap.c:3465 > call_write_iter include/linux/fs.h:1890 [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/0x760 arch/x86/entry/common.c:290 > 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:4487 > down_write+0x93/0x150 kernel/locking/rwsem.c:1534 > inode_lock include/linux/fs.h:789 [inline] > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 > 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/0xa30 mm/vmscan.c:560 > shrink_slab mm/vmscan.c:721 [inline] > shrink_slab+0x19a/0x680 mm/vmscan.c:694 > shrink_node+0x223/0x12e0 mm/vmscan.c:2807 > kswapd_shrink_node mm/vmscan.c:3549 [inline] > balance_pgdat+0x57c/0xea0 mm/vmscan.c:3707 > kswapd+0x5c3/0xf30 mm/vmscan.c:3958 > 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 kswapd0/1770: > #0: ffffffff89042f80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 > mm/page_alloc.c:4889 > #1: ffffffff8901ffe8 (shrinker_rwsem){++++}, at: shrink_slab > mm/vmscan.c:711 [inline] > #1: ffffffff8901ffe8 (shrinker_rwsem){++++}, at: shrink_slab+0xe6/0x680 > mm/vmscan.c:694 > > stack backtrace: > CPU: 0 PID: 1770 Comm: kswapd0 Not tainted 5.3.0-rc6-next-20190830 #75 > 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+0x172/0x1f0 lib/dump_stack.c:113 > 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:4487 > down_write+0x93/0x150 kernel/locking/rwsem.c:1534 > inode_lock include/linux/fs.h:789 [inline] > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 > 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/0xa30 mm/vmscan.c:560 > shrink_slab mm/vmscan.c:721 [inline] > shrink_slab+0x19a/0x680 mm/vmscan.c:694 > shrink_node+0x223/0x12e0 mm/vmscan.c:2807 > kswapd_shrink_node mm/vmscan.c:3549 [inline] > balance_pgdat+0x57c/0xea0 mm/vmscan.c:3707 > kswapd+0x5c3/0xf30 mm/vmscan.c:3958 > kthread+0x361/0x430 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 It burns more than pure cpu cycles to check anything against kswapd in terms of __GFP_FS, so fix 93781325da6e and d92a8cfcb37e. --- works/jj/vmscan.c 2019-09-10 14:52:00.602771300 +0800 +++ works/zz/vmscan.c 2019-09-10 14:54:48.101915500 +0800 @@ -3593,7 +3593,6 @@ static int balance_pgdat(pg_data_t *pgda set_task_reclaim_state(current, &sc.reclaim_state); psi_memstall_enter(&pflags); - __fs_reclaim_acquire(); count_vm_event(PAGEOUTRUN); @@ -3718,9 +3717,7 @@ restart: wake_up_all(&pgdat->pfmemalloc_wait); /* Check if kswapd should be suspending */ - __fs_reclaim_release(); ret = try_to_freeze(); - __fs_reclaim_acquire(); if (ret || kthread_should_stop()) break; @@ -3770,7 +3767,6 @@ out: } snapshot_refaults(NULL, pgdat); - __fs_reclaim_release(); psi_memstall_leave(&pflags); set_task_reclaim_state(current, NULL); --
