possible circular lock dependency

possible circular lock dependency

[Steve French]

Saw possible lock dependency problem (once) running cifs/102 test -
ran multiple times but only saw once.  It may be fixed by later
patches from Shyam, but I was doing some tests with only his first
two.

This is on on 5.17-rc3 + the 3 patches below.
52492ff5c583 cifs: call helper functions for marking channels for reconnect
a81da65fbae6 cifs: call cifs_reconnect when a connection is marked
d0cbe56a7d5a [smb3] improve error message when mount options conflict with posix
dfd42facf1e4 (tag: v5.17-rc3, origin/master, origin/HEAD,
linus/master, master) Linux 5.17-rc3

[ 6566.222316] run fstests cifs/102 at 2022-02-12 02:27:53

[ 6567.213971] ======================================================
[ 6567.214280] WARNING: possible circular locking dependency detected
[ 6567.214496] 5.17.0-rc3 #1 Not tainted
[ 6567.214851] ------------------------------------------------------
[ 6567.214851] cifsd/5791 is trying to acquire lock:
[ 6567.214851] ffffffffc0b296f8 (&cifs_tcp_ses_lock){+.+.}-{2:2}, at:
smb2_find_smb_tcon+0x24/0xc0 [cifs]
[ 6567.215501]
               but task is already holding lock:
[ 6567.215501] ffffffffc0b29698 (&GlobalMid_Lock){+.+.}-{2:2}, at:
cifs_mid_q_entry_release+0x22/0x610 [cifs]
[ 6567.216247]
               which lock already depends on the new lock.

[ 6567.216661]
               the existing dependency chain (in reverse order) is:
[ 6567.217496]
               -> #1 (&GlobalMid_Lock){+.+.}-{2:2}:
[ 6567.217991]        _raw_spin_lock+0x2f/0x40
[ 6567.217991]        cifs_debug_data_proc_show+0x50c/0x9b0 [cifs]
[ 6567.217991]        seq_read_iter+0xd3/0x440
[ 6567.217991]        proc_reg_read_iter+0x46/0x60
[ 6567.219094]        new_sync_read+0x10e/0x180
[ 6567.219094]        vfs_read+0x171/0x1a0
[ 6567.219560]        ksys_read+0x87/0xc0
[ 6567.219585]        do_syscall_64+0x3a/0x80
[ 6567.219585]        entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 6567.219585]
               -> #0 (&cifs_tcp_ses_lock){+.+.}-{2:2}:
[ 6567.220786]        __lock_acquire+0x1302/0x18d0
[ 6567.220786]        lock_acquire+0x267/0x330
[ 6567.221479]        _raw_spin_lock+0x2f/0x40
[ 6567.221479]        smb2_find_smb_tcon+0x24/0xc0 [cifs]
[ 6567.221479]        smb2_handle_cancelled_mid+0x3e/0x90 [cifs]
[ 6567.221479]        cifs_mid_q_entry_release+0x28a/0x610 [cifs]
[ 6567.223102]        cifs_demultiplex_thread+0x848/0xf70 [cifs]
[ 6567.223102]        kthread+0xe8/0x110
[ 6567.223642]        ret_from_fork+0x22/0x30
[ 6567.223642]
               other info that might help us debug this:

[ 6567.223642]  Possible unsafe locking scenario:

[ 6567.225550]        CPU0                    CPU1
[ 6567.225550]        ----                    ----
[ 6567.225550]   lock(&GlobalMid_Lock);
[ 6567.225550]                                lock(&cifs_tcp_ses_lock);
[ 6567.228648]                                lock(&GlobalMid_Lock);
[ 6567.228648]   lock(&cifs_tcp_ses_lock);
[ 6567.229647]
                *** DEADLOCK ***

[ 6567.230447] 1 lock held by cifsd/5791:
[ 6567.231573]  #0: ffffffffc0b29698 (&GlobalMid_Lock){+.+.}-{2:2},
at: cifs_mid_q_entry_release+0x22/0x610 [cifs]
[ 6567.232498]
               stack backtrace:
[ 6567.232630] CPU: 3 PID: 5791 Comm: cifsd Not tainted 5.17.0-rc3 #1
[ 6567.232630] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 6567.234451] Call Trace:
[ 6567.234451]  <TASK>
[ 6567.234451]  dump_stack_lvl+0x58/0x71
[ 6567.234451]  check_noncircular+0xe7/0x100
[ 6567.234451]  ? __lock_acquire+0xb7e/0x18d0
[ 6567.234451]  ? __lock_acquire+0x1302/0x18d0
[ 6567.234451]  __lock_acquire+0x1302/0x18d0
[ 6567.234451]  lock_acquire+0x267/0x330
[ 6567.234451]  ? smb2_find_smb_tcon+0x24/0xc0 [cifs]
[ 6567.234451]  _raw_spin_lock+0x2f/0x40
[ 6567.234451]  ? smb2_find_smb_tcon+0x24/0xc0 [cifs]
[ 6567.234451]  smb2_find_smb_tcon+0x24/0xc0 [cifs]
[ 6567.240749]  smb2_handle_cancelled_mid+0x3e/0x90 [cifs]
[ 6567.240749]  ? _raw_spin_lock+0x2f/0x40
[ 6567.240749]  cifs_mid_q_entry_release+0x28a/0x610 [cifs]
[ 6567.240749]  ? lock_release+0x1db/0x2b0
[ 6567.240749]  cifs_demultiplex_thread+0x848/0xf70 [cifs]
[ 6567.240749]  ? cifs_handle_standard+0x210/0x210 [cifs]
[ 6567.240749]  kthread+0xe8/0x110
[ 6567.240749]  ? kthread_complete_and_exit+0x20/0x20
[ 6567.240749]  ret_from_fork+0x22/0x30
[ 6567.240749]  </TASK>
[ 6567.252563] CIFS: VFS: \\win16.vm.test\Share Close unmatched open for MID:404
[ 6567.256753] CIFS: VFS: \\win16.vm.test\Share Close unmatched open for MID:405
[ 6567.269283] CIFS: VFS: \\win16.vm.test\Share Close unmatched open for MID:407
[ 6567.271962] CIFS: VFS: \\win16.vm.test\Share Close unmatched open for MID:408


-- 
Thanks,

Steve