possible deadlock in shmem_fallocate (3)
Quoted 122 lines
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 [email protected]======================================================
WARNING: possible circular locking dependency detected 5.3.0-rc6-next-20190830 #75 Not tainted
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kswapd0/1770 is trying to acquire lock:ffff8880a0b9b780(&sb->s_type->i_mutex_key#13){+.+.}, at:inode_lockinclude/linux/fs.h:789[inline]ffff8880a0b9b780(&sb->s_type->i_mutex_key#13){+.+.}, at:shmem_fallocate+0x15a/0xc60mm/shmem.c:2728but task is already holding lock:
ffffffff89042f80(fs_reclaim){+.+.}, at:__fs_reclaim_acquire+0x0/0x30mm/page_alloc.c:4889which 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:352other 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+0x0/0x30mm/page_alloc.c:4889
#1:ffffffff8901ffe8(shrinker_rwsem){++++}, at:shrink_slabmm/vmscan.c:711[inline]
#1:ffffffff8901ffe8(shrinker_rwsem){++++}, at:shrink_slab+0xe6/0x680mm/vmscan.c:694stack 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
Quoted 8 lines
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.
zz/vmscan.c renamed from jj/vmscan.c +0 -4
@@ -3593,7 +3593,6 @@ static int balance_pgdat(pg_data_t *pgdaset_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 );
--