Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <d5b65b01-62a9-e483-dea8-5e2bb65be278@redhat.com>
Date:   Tue, 9 May 2023 16:27:46 -0400
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: [PATCH 03/32] locking/lockdep: lockdep_set_no_check_recursion()
Content-Language: en-US
To:     Kent Overstreet <kent.overstreet@linux.dev>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-bcachefs@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Will Deacon <will@kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>
References: <20230509165657.1735798-1-kent.overstreet@linux.dev>
 <20230509165657.1735798-4-kent.overstreet@linux.dev>
 <20230509193147.GC2148518@hirez.programming.kicks-ass.net>
 <ZFqqsyDpatgb77Vh@moria.home.lan>
From:   Waiman Long <longman@redhat.com>
In-Reply-To: <ZFqqsyDpatgb77Vh@moria.home.lan>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 5/9/23 16:18, Kent Overstreet wrote:
> On Tue, May 09, 2023 at 09:31:47PM +0200, Peter Zijlstra wrote:
>> On Tue, May 09, 2023 at 12:56:28PM -0400, Kent Overstreet wrote:
>>> This adds a method to tell lockdep not to check lock ordering within a
>>> lock class - but to still check lock ordering w.r.t. other lock types.
>>>
>>> This is for bcachefs, where for btree node locks we have our own
>>> deadlock avoidance strategy w.r.t. other btree node locks (cycle
>>> detection), but we still want lockdep to check lock ordering w.r.t.
>>> other lock types.
>>>
>> ISTR you had a much nicer version of this where you gave a custom order
>> function -- what happend to that?
> Actually, I spoke too soon; this patch and the other series with the
> comparison function solve different problems.
>
> For bcachefs btree node locks, we don't have a defined lock ordering at
> all - we do full runtime cycle detection, so we don't want lockdep
> checking for self deadlock because we're handling that but we _do_ want
> lockdep checking lock ordering of btree node locks w.r.t. other locks in
> the system.

Maybe you can use lock_set_novalidate_class() instead.

Cheers,
Longman