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[71.43.216.131]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-56ae35d455fsm6387070e0c.4.2026.03.05.03.08.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Mar 2026 03:08:51 -0800 (PST) Message-ID: <6d40385d-e447-4cb4-b327-bb10aa6a8563@kernel.dk> Date: Thu, 5 Mar 2026 04:08:50 -0700 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Jens Axboe Subject: Re: [PATCH] block: use trylock to avoid lockdep circular dependency in sysfs To: Ming Lei , linux-block@vger.kernel.org Cc: Yi Zhang References: <20260305031550.1161328-1-ming.lei@redhat.com> Content-Language: en-US In-Reply-To: <20260305031550.1161328-1-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/4/26 8:15 PM, Ming Lei wrote: > Use trylock instead of blocking lock acquisition for update_nr_hwq_lock > in queue_requests_store() and elv_iosched_store() to avoid circular lock > dependency with kernfs active reference during concurrent disk deletion: > > update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del) > kn->active -> update_nr_hwq_lock (via sysfs write path) > > Return -EBUSY when the lock is not immediately available. This does mean that scripts can get spurious -EBUSY they now need to handle. Which probably isn't a big real world problem. While it isn't a hard thing to fix up in a script, it can potentially break existing setups. Not sure I see a good way around that however, without queueing these to a clean context and having the store helpers wait on eg work item being processed and completed. Hopefully this will never be a thing and we'll never need to discuss this issue, I'll get this one applied for now. -- Jens Axboe