I hit the following lockdep splat during some regression testing today, and
was able to reproduce it on vanilla v4.11 without DAX. My test setup is big
memmap PMEM device in a QEMU virtual machine, but I don't think that the block
device is important. I was able to reproduce this easily by running
generic/386 in a loop. Here's the failure:
FSTYP -- ext4
PLATFORM -- Linux/x86_64 lorwyn 4.11.0
MKFS_OPTIONS -- /dev/pmem0p2
MOUNT_OPTIONS -- -o acl,user_xattr -o context=system_u:object_r:root_t:s0 /dev/pmem0p2 /mnt/xfstests_scratch
generic/386 1s ... 1s
_check_dmesg: something found in dmesg (see /root/xfstests/results//generic/386.dmesg)
Ran: generic/386
Failures: generic/386
Failed 1 of 1 tests
Here's the lockdep splat, passed through kasan_symbolize.py:
run fstests generic/386 at 2017-05-04 13:36:35
EXT4-fs (pmem0p2): mounted filesystem with ordered data mode. Opts: acl,user_xattr,quota
======================================================
[ INFO: possible circular locking dependency detected ]
4.11.0 #1 Not tainted
-------------------------------------------------------
mkdir/8458 is trying to acquire lock:
(&s->s_dquot.dqio_mutex){+.+...}, at: [<ffffffff8133a8bb>] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
but task is already holding lock:
(&ei->i_data_sem/2){++++..}, at: [<ffffffff81371ba1>] ext4_map_blocks+0x151/0x5e0 fs/ext4/inode.c:612
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&ei->i_data_sem/2){++++..}:
[< none >] lock_acquire+0xea/0x1f0 kernel/locking/lockdep.c:3762
[< none >] down_read+0x43/0xa0 kernel/locking/rwsem.c:23
[< none >] ext4_map_blocks+0x2b4/0x5e0 fs/ext4/inode.c:540
[< none >] ext4_getblk+0x51/0x1a0 fs/ext4/inode.c:949
[< none >] ext4_bread+0x22/0xc0 fs/ext4/inode.c:999
[< none >] ext4_quota_read+0xce/0x110 fs/ext4/super.c:5470
[< none >] read_blk+0x4c/0x60 fs/quota/quota_tree.c:63
[< none >] find_tree_dqentry+0x44/0x230 fs/quota/quota_tree.c:579
[< none >] find_tree_dqentry+0x1ad/0x230 fs/quota/quota_tree.c:590
[< none >] find_tree_dqentry+0x1ad/0x230 fs/quota/quota_tree.c:590
[< none >] find_tree_dqentry+0x1ad/0x230 fs/quota/quota_tree.c:590
[< inline >] find_dqentry fs/quota/quota_tree.c:602
[< none >] qtree_read_dquot+0x12e/0x260 fs/quota/quota_tree.c:622
[< none >] v2_read_dquot+0x2e/0x30 fs/quota/quota_v2.c:288
[< none >] dquot_acquire+0xe3/0x120 fs/quota/dquot.c:411
[< none >] ext4_acquire_dquot+0x68/0xa0 fs/ext4/super.c:5227
[< none >] dqget+0x305/0x470 fs/quota/dquot.c:891
[< none >] __dquot_initialize+0x151/0x290 fs/quota/dquot.c:1460
[< none >] dquot_initialize+0x13/0x20 fs/quota/dquot.c:1511
[< none >] ext4_mkdir+0x66/0x470 fs/ext4/namei.c:2645
[< none >] vfs_mkdir+0x119/0x1c0 fs/namei.c:3769
[< inline >] SYSC_mkdirat fs/namei.c:3792
[< inline >] SyS_mkdirat fs/namei.c:3776
[< inline >] SYSC_mkdir fs/namei.c:3803
[< none >] SyS_mkdir+0x7a/0xf0 fs/namei.c:3801
[< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:204
-> #0 (&s->s_dquot.dqio_mutex){+.+...}:
[< inline >] check_prev_add kernel/locking/lockdep.c:1830
[< inline >] check_prevs_add kernel/locking/lockdep.c:1940
[< inline >] validate_chain kernel/locking/lockdep.c:2267
[< none >] __lock_acquire+0x12c2/0x1450 kernel/locking/lockdep.c:3347
[< none >] lock_acquire+0xea/0x1f0 kernel/locking/lockdep.c:3762
[< inline >] __mutex_lock_common kernel/locking/mutex.c:756
[< none >] __mutex_lock+0x8d/0xa80 kernel/locking/mutex.c:893
[< none >] mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:908
[< none >] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
[< none >] ext4_write_dquot+0x6f/0xa0 fs/ext4/super.c:5211
[< none >] ext4_mark_dquot_dirty+0x3f/0x60 fs/ext4/super.c:5262
[< inline >] mark_dquot_dirty fs/quota/dquot.c:337
[< inline >] mark_all_dquot_dirty fs/quota/dquot.c:369
[< none >] __dquot_alloc_space+0x275/0x2b0 fs/quota/dquot.c:1693
[< inline >] dquot_alloc_space_nodirty ./include/linux/quotaops.h:284
[< inline >] dquot_alloc_space ./include/linux/quotaops.h:297
[< inline >] dquot_alloc_block ./include/linux/quotaops.h:321
[< none >] ext4_mb_new_blocks+0x113/0x1110 fs/ext4/mballoc.c:4487
[< none >] ext4_ext_map_blocks+0xe2f/0x20d0 fs/ext4/extents.c:4478
[< none >] ext4_map_blocks+0x175/0x5e0 fs/ext4/inode.c:619
[< none >] ext4_getblk+0x51/0x1a0 fs/ext4/inode.c:949
[< none >] ext4_bread+0x22/0xc0 fs/ext4/inode.c:999
[< none >] ext4_append+0x4d/0xe0 fs/ext4/namei.c:64
[< inline >] ext4_init_new_dir fs/ext4/namei.c:2615
[< none >] ext4_mkdir+0x266/0x470 fs/ext4/namei.c:2662
[< none >] vfs_mkdir+0x119/0x1c0 fs/namei.c:3769
[< inline >] SYSC_mkdirat fs/namei.c:3792
[< inline >] SyS_mkdirat fs/namei.c:3776
[< inline >] SYSC_mkdir fs/namei.c:3803
[< none >] SyS_mkdir+0x7a/0xf0 fs/namei.c:3801
[< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:204
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&ei->i_data_sem/2);
lock(&s->s_dquot.dqio_mutex);
lock(&ei->i_data_sem/2);
lock(&s->s_dquot.dqio_mutex);
*** DEADLOCK ***
5 locks held by mkdir/8458:
#0: (sb_writers#14){.+.+.+}, at: [< inline >] sb_start_write ./include/linux/fs.h:1504
#0: (sb_writers#14){.+.+.+}, at: [<ffffffff812e1e24>] mnt_want_write+0x24/0x50 fs/namespace.c:388
#1: (&type->i_mutex_dir_key#5/1){+.+.+.}, at: [< inline >] inode_lock_nested ./include/linux/fs.h:731
#1: (&type->i_mutex_dir_key#5/1){+.+.+.}, at: [<ffffffff812cb5e3>] filename_create+0x83/0x160 fs/namei.c:3594
#2: (jbd2_handle){++++..}, at: [<ffffffff813d31b2>] start_this_handle+0x112/0x450 fs/jbd2/transaction.c:361
#3: (&ei->i_data_sem/2){++++..}, at: [<ffffffff81371ba1>] ext4_map_blocks+0x151/0x5e0 fs/ext4/inode.c:612
#4: (dquot_srcu){......}, at: [< inline >] srcu_read_lock ./include/linux/srcu.h:237
#4: (dquot_srcu){......}, at: [<ffffffff8133c44b>] __dquot_alloc_space+0xbb/0x2b0 fs/quota/dquot.c:1668
stack backtrace:
CPU: 3 PID: 8458 Comm: mkdir Not tainted 4.11.0 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:16
[< none >] dump_stack+0x86/0xc3 lib/dump_stack.c:52
[< none >] print_circular_bug+0x1be/0x210 kernel/locking/lockdep.c:1204
[< inline >] check_prev_add kernel/locking/lockdep.c:1830
[< inline >] check_prevs_add kernel/locking/lockdep.c:1940
[< inline >] validate_chain kernel/locking/lockdep.c:2267
[< none >] __lock_acquire+0x12c2/0x1450 kernel/locking/lockdep.c:3347
[< none >] lock_acquire+0xea/0x1f0 kernel/locking/lockdep.c:3762
?[< none >] lock_acquire+0xea/0x1f0 kernel/locking/lockdep.c:3762
?[< none >] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
?[< none >] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
[< inline >] __mutex_lock_common kernel/locking/mutex.c:756
[< none >] __mutex_lock+0x8d/0xa80 kernel/locking/mutex.c:893
?[< none >] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
?[< inline >] spin_unlock ./include/linux/spinlock.h:339
?[< none >] dquot_mark_dquot_dirty+0x57/0xc0 fs/quota/dquot.c:355
?[< inline >] __ext4_journal_start fs/ext4/ext4_jbd2.h:318
?[< none >] ext4_write_dquot+0x5c/0xa0 fs/ext4/super.c:5207
?[< inline >] __ext4_journal_start fs/ext4/ext4_jbd2.h:318
?[< none >] ext4_write_dquot+0x5c/0xa0 fs/ext4/super.c:5207
[< none >] mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:908
?[< none >] mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:908
[< none >] dquot_commit+0x2b/0xd0 fs/quota/dquot.c:453
[< none >] ext4_write_dquot+0x6f/0xa0 fs/ext4/super.c:5211
[< none >] ext4_mark_dquot_dirty+0x3f/0x60 fs/ext4/super.c:5262
[< inline >] mark_dquot_dirty fs/quota/dquot.c:337
[< inline >] mark_all_dquot_dirty fs/quota/dquot.c:369
[< none >] __dquot_alloc_space+0x275/0x2b0 fs/quota/dquot.c:1693
?[< none >] __this_cpu_preempt_check+0x13/0x20 lib/smp_processor_id.c:62
?[< none >] __percpu_counter_add+0x85/0xb0 lib/percpu_counter.c:90
[< inline >] dquot_alloc_space_nodirty ./include/linux/quotaops.h:284
[< inline >] dquot_alloc_space ./include/linux/quotaops.h:297
[< inline >] dquot_alloc_block ./include/linux/quotaops.h:321
[< none >] ext4_mb_new_blocks+0x113/0x1110 fs/ext4/mballoc.c:4487
?[< inline >] lock_is_held ./include/linux/lockdep.h:348
?[< none >] rcu_read_lock_sched_held+0x4a/0x80 kernel/rcu/update.c:114
?[< inline >] trace_kmalloc ./include/trace/events/kmem.h:45
?[< none >] __kmalloc+0x2ce/0x300 mm/slub.c:3743
?[< inline >] kmalloc ./include/linux/slab.h:495
?[< inline >] kzalloc ./include/linux/slab.h:663
?[< none >] ext4_find_extent+0x295/0x2d0 fs/ext4/extents.c:894
?[< inline >] kmalloc ./include/linux/slab.h:495
?[< inline >] kzalloc ./include/linux/slab.h:663
?[< none >] ext4_find_extent+0x295/0x2d0 fs/ext4/extents.c:894
[< none >] ext4_ext_map_blocks+0xe2f/0x20d0 fs/ext4/extents.c:4478
?[< none >] ext4_map_blocks+0x331/0x5e0 fs/ext4/inode.c:571
?[< none >] ext4_map_blocks+0x331/0x5e0 fs/ext4/inode.c:571
[< none >] ext4_map_blocks+0x175/0x5e0 fs/ext4/inode.c:619
[< none >] ext4_getblk+0x51/0x1a0 fs/ext4/inode.c:949
[< none >] ext4_bread+0x22/0xc0 fs/ext4/inode.c:999
[< none >] ext4_append+0x4d/0xe0 fs/ext4/namei.c:64
[< inline >] ext4_init_new_dir fs/ext4/namei.c:2615
[< none >] ext4_mkdir+0x266/0x470 fs/ext4/namei.c:2662
[< none >] vfs_mkdir+0x119/0x1c0 fs/namei.c:3769
[< inline >] SYSC_mkdirat fs/namei.c:3792
[< inline >] SyS_mkdirat fs/namei.c:3776
[< inline >] SYSC_mkdir fs/namei.c:3803
[< none >] SyS_mkdir+0x7a/0xf0 fs/namei.c:3801
[< none >] entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:204
RIP: 0033:0x7fb614c15947
RSP: 002b:00007fff31be4938 EFLAGS: 00000216 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007fff31be4c48 RCX: 00007fb614c15947
RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007fff31be6aa5
RBP: 0000000000000003 R08: 00000000000001ff R09: 0000564258eadac0
R10: 000056425b0a4060 R11: 0000000000000216 R12: 0000000000000000
R13: 0000564258eadb00 R14: 0000000000000000 R15: 0000000000000000
