Re: [PATCH 13/14] cifs: display the endpoint IP details in DebugData

[Paulo Alcantara <pc@manguebit.com>]

Hi Shyam,

Shyam Prasad N <nspmangalore@gmail.com> writes:

> On Wed, Nov 1, 2023 at 7:42 PM Paulo Alcantara <pc@manguebit.com> wrote:
>>
>> Paulo Alcantara <pc@manguebit.com> writes:
>>
>> >> @@ -515,7 +573,18 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
>> >>                              seq_printf(m, "\n\n\tExtra Channels: %zu ",
>> >>                                         ses->chan_count-1);
>> >>                              for (j = 1; j < ses->chan_count; j++) {
>> >> +                                    /*
>> >> +                                     * kernel_getsockname can block inside
>> >> +                                     * cifs_dump_channel. so drop the lock first
>> >> +                                     */
>> >> +                                    server->srv_count++;
>> >> +                                    spin_unlock(&cifs_tcp_ses_lock);
>> >> +
>> >>                                      cifs_dump_channel(m, j, &ses->chans[j]);
>> >> +
>> >> +                                    cifs_put_tcp_session(server, 0);
>> >> +                                    spin_lock(&cifs_tcp_ses_lock);
>> >
>> > Here you are re-acquiring @cifs_tcp_ses_lock spinlock under
>> > @ses->chan_lock, which will introduce deadlocks in threads calling
>> > cifs_match_super(), cifs_signal_cifsd_for_reconnect(),
>> > cifs_mark_tcp_ses_conns_for_reconnect(), cifs_find_smb_ses(), ...
>>
>
> Good points.
> I'm just wondering why I'm unable to repro the same though.
> I have lockdep enabled on my kernel too. But the same steps do not
> throw this warning.

That's weird as I can always reproduce it when mounting a Windows Server
2022 share with 'username=foo,password=bar,multichannel' options
followed by `cat /proc/fs/cifs/DebugData`.

Here is the relevant part of my .config

#
# Lock Debugging (spinlocks, mutexes, etc...)
#
CONFIG_LOCK_DEBUGGING_SUPPORT=y
CONFIG_PROVE_LOCKING=y
# CONFIG_PROVE_RAW_LOCK_NESTING is not set
CONFIG_LOCK_STAT=y
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y
CONFIG_DEBUG_RWSEMS=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_LOCKDEP=y
CONFIG_LOCKDEP_BITS=15
CONFIG_LOCKDEP_CHAINS_BITS=16
CONFIG_LOCKDEP_STACK_TRACE_BITS=19
CONFIG_LOCKDEP_STACK_TRACE_HASH_BITS=14
CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12
# CONFIG_DEBUG_LOCKDEP is not set
CONFIG_DEBUG_ATOMIC_SLEEP=y
# CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
# CONFIG_LOCK_TORTURE_TEST is not set
# CONFIG_WW_MUTEX_SELFTEST is not set
# CONFIG_SCF_TORTURE_TEST is not set
# CONFIG_CSD_LOCK_WAIT_DEBUG is not set
# end of Lock Debugging (spinlocks, mutexes, etc...)