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Subjectpossible circular locking dependency detected [was: linux-next: Tree for Aug 22]
Hello,

======================================================
WARNING: possible circular locking dependency detected
4.13.0-rc6-next-20170822-dbg-00020-g39758ed8aae0-dirty #1746 Not tainted
------------------------------------------------------
fsck.ext4/148 is trying to acquire lock:
(&bdev->bd_mutex){+.+.}, at: [<ffffffff8116e73e>] __blkdev_put+0x33/0x190

but now in release context of a crosslock acquired at the following:
((complete)&wait#2){+.+.}, at: [<ffffffff812159e0>] blk_execute_rq+0xbb/0xda

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 ((complete)&wait#2){+.+.}:
lock_acquire+0x176/0x19e
__wait_for_common+0x50/0x1e3
blk_execute_rq+0xbb/0xda
scsi_execute+0xc3/0x17d [scsi_mod]
sd_revalidate_disk+0x112/0x1549 [sd_mod]
rescan_partitions+0x48/0x2c4
__blkdev_get+0x14b/0x37c
blkdev_get+0x191/0x2c0
device_add_disk+0x2b4/0x3e5
sd_probe_async+0xf8/0x17e [sd_mod]
async_run_entry_fn+0x34/0xe0
process_one_work+0x2af/0x4d1
worker_thread+0x19a/0x24f
kthread+0x133/0x13b
ret_from_fork+0x27/0x40

-> #0 (&bdev->bd_mutex){+.+.}:
__blkdev_put+0x33/0x190
blkdev_close+0x24/0x27
__fput+0xee/0x18a
task_work_run+0x79/0xa0
prepare_exit_to_usermode+0x9b/0xb5

other info that might help us debug this:
Possible unsafe locking scenario by crosslock:
CPU0 CPU1
---- ----
lock(&bdev->bd_mutex);
lock((complete)&wait#2);
lock(&bdev->bd_mutex);
unlock((complete)&wait#2);

*** DEADLOCK ***
4 locks held by fsck.ext4/148:
#0: (&bdev->bd_mutex){+.+.}, at: [<ffffffff8116e73e>] __blkdev_put+0x33/0x190
#1: (rcu_read_lock){....}, at: [<ffffffff81217f16>] rcu_lock_acquire+0x0/0x20
#2: (&(&host->lock)->rlock){-.-.}, at: [<ffffffffa00e7550>] ata_scsi_queuecmd+0x23/0x74 [libata]
#3: (&x->wait#14){-...}, at: [<ffffffff8106b593>] complete+0x18/0x50

stack backtrace:
CPU: 1 PID: 148 Comm: fsck.ext4 Not tainted 4.13.0-rc6-next-20170822-dbg-00020-g39758ed8aae0-dirty #1746
Call Trace:
dump_stack+0x67/0x8e
print_circular_bug+0x2a1/0x2af
? zap_class+0xc5/0xc5
check_prev_add+0x76/0x20d
? __lock_acquire+0xc27/0xcc8
lock_commit_crosslock+0x327/0x35e
complete+0x24/0x50
scsi_end_request+0x8d/0x176 [scsi_mod]
scsi_io_completion+0x1be/0x423 [scsi_mod]
__blk_mq_complete_request+0x112/0x131
ata_scsi_simulate+0x212/0x218 [libata]
__ata_scsi_queuecmd+0x1be/0x1de [libata]
ata_scsi_queuecmd+0x41/0x74 [libata]
scsi_dispatch_cmd+0x194/0x2af [scsi_mod]
scsi_queue_rq+0x1e0/0x26f [scsi_mod]
blk_mq_dispatch_rq_list+0x193/0x2a7
? _raw_spin_unlock+0x2e/0x40
blk_mq_sched_dispatch_requests+0x132/0x176
__blk_mq_run_hw_queue+0x59/0xc5
__blk_mq_delay_run_hw_queue+0x5f/0xc1
blk_mq_flush_plug_list+0xfc/0x10b
blk_flush_plug_list+0xc6/0x1eb
blk_finish_plug+0x25/0x32
generic_writepages+0x56/0x63
do_writepages+0x36/0x70
__filemap_fdatawrite_range+0x59/0x5f
filemap_write_and_wait+0x19/0x4f
__blkdev_put+0x5f/0x190
blkdev_close+0x24/0x27
__fput+0xee/0x18a
task_work_run+0x79/0xa0
prepare_exit_to_usermode+0x9b/0xb5
entry_SYSCALL_64_fastpath+0xab/0xad
RIP: 0033:0x7ff5755a2f74
RSP: 002b:00007ffe46fce038 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000555ddeddded0 RCX: 00007ff5755a2f74
RDX: 0000000000001000 RSI: 0000555ddede2580 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000555ddede2580 R09: 0000555ddedde080
R10: 0000000108000000 R11: 0000000000000246 R12: 0000555ddedddfa0
R13: 00007ff576523680 R14: 0000000000001000 R15: 0000555ddeddc2b0

-ss

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