======================================================
WARNING: possible circular locking dependency detected
4.14.131+ #13 Not tainted
------------------------------------------------------
syz-executor.2/18125 is trying to acquire lock:
 (cpu_hotplug_lock.rw_sem){++++}, at: [<00000000b889ece6>] get_online_cpus include/linux/cpu.h:140 [inline]
 (cpu_hotplug_lock.rw_sem){++++}, at: [<00000000b889ece6>] lru_add_drain_all+0xa/0x20 mm/swap.c:729

but task is already holding lock:
 (&sb->s_type->i_mutex_key#10){+.+.}, at: [<000000008607751a>] inode_lock include/linux/fs.h:718 [inline]
 (&sb->s_type->i_mutex_key#10){+.+.}, at: [<000000008607751a>] shmem_add_seals+0x12b/0x1150 mm/shmem.c:2829

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&sb->s_type->i_mutex_key#10){+.+.}:

-> #4 (ashmem_mutex){+.+.}:

-> #3 (&mm->mmap_sem){++++}:

-> #2 (&cpuctx_mutex){+.+.}:

-> #1 (pmus_lock){+.+.}:

-> #0 (cpu_hotplug_lock.rw_sem){++++}:

other info that might help us debug this:

Chain exists of:
  cpu_hotplug_lock.rw_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#10

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#10);
                               lock(ashmem_mutex);
                               lock(&sb->s_type->i_mutex_key#10);
  lock(cpu_hotplug_lock.rw_sem);

 *** DEADLOCK ***

1 lock held by syz-executor.2/18125:
 #0:  (&sb->s_type->i_mutex_key#10){+.+.}, at: [<000000008607751a>] inode_lock include/linux/fs.h:718 [inline]
 #0:  (&sb->s_type->i_mutex_key#10){+.+.}, at: [<000000008607751a>] shmem_add_seals+0x12b/0x1150 mm/shmem.c:2829

stack backtrace:
CPU: 1 PID: 18125 Comm: syz-executor.2 Not tainted 4.14.131+ #13
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258
print_req_error: I/O error, dev loop4, sector 0
print_req_error: I/O error, dev loop4, sector 392
Buffer I/O error on dev loop4, logical block 49, lost async page write
print_req_error: I/O error, dev loop4, sector 256
Buffer I/O error on dev loop4, logical block 32, lost async page write
print_req_error: I/O error, dev loop4, sector 136
Buffer I/O error on dev loop4, logical block 17, lost async page write
print_req_error: I/O error, dev loop4, sector 304
Buffer I/O error on dev loop4, logical block 38, lost async page write
print_req_error: I/O error, dev loop4, sector 208
Buffer I/O error on dev loop4, logical block 26, lost async page write
print_req_error: I/O error, dev loop4, sector 384
Buffer I/O error on dev loop4, logical block 48, lost async page write
print_req_error: I/O error, dev loop4, sector 256
Buffer I/O error on dev loop4, logical block 32, lost async page write
print_req_error: I/O error, dev loop4, sector 768
Buffer I/O error on dev loop4, logical block 96, lost async page write
print_req_error: I/O error, dev loop4, sector 256
Buffer I/O error on dev loop4, logical block 32, lost async page write
print_req_error: I/O error, dev loop4, sector 256
Buffer I/O error on dev loop4, logical block 32, lost async page write