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Wed, 11 Nov 2026 03:38:27 -0800 (PST) Received: from fedora ([187.120.157.132]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b393426f13sm42133187b3.34.2026.11.11.03.38.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 03:38:27 -0800 (PST) From: Guilherme Giacomo Simoes To: trintaeoitogc@gmail.com Cc: axboe@kernel.dk, bvanassche@acm.org, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org, syzbot+d7d72f3d467710442af0@syzkaller.appspotmail.com Subject: Re: [PATCH] nbd: fix circular lock dependency Date: Wed, 11 Nov 2026 08:38:14 -0300 Message-ID: <20261111113814.221685-1-trintaeoitogc@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20261111101919.215767-1-trintaeoitogc@gmail.com> References: <20261111101919.215767-1-trintaeoitogc@gmail.com> X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Guilherme Giacomo Simoes wrote: > > There is no real circular lock dependency here. This patch addresses a > > lockdep false positive caused by the missing socket reclassification in > > the reconnect path. Please change the subject into something like > > "nbd: Also reclassify sockets in the reconnect path". > > > > > instead of the NBD-specific class leading to a possible lock dependency. > > > > Please change "possible lock dependency" into "lockdep false positive". > > > > > Reported-by: syzbot+d7d72f3d467710442af0@syzkaller.appspotmail.com > > > Link: https://syzkaller.appspot.com/bug?extid=d7d72f3d467710442af0 > > > > Please use Closes: instead of Link: for the syzbot report. > Ok, I will send a V2 What do you think: ``` nbd: must reclassify socket when socket is created When we need to connect or reconnect a new socket, we need to call nbd_reclassify_socket() to ensure that a false positive lock_dep circular warning fires. Inside nbd_add_socket(), after nbd_get_socket() call he already call nbd_reclassify_socket(). However inside nbd_genl_reconnect_sock_cb() the nbd_reclassify_socket() must be called too and this is not doing. To ensure that even when nbd_get_socket() is called the nbd_reclassify_socket() will be called to, put the nbd_reclassify_socket() inside nbd_get_socket(). Move the nbd_get_socket() bellow of nbd_reclassify_socket(). nbd_add_socket() no longer needs to do it. ``` ? > > If the reclassification should happen in nbd_get_socket(), please move > > nbd_reclassify_socket() up instead of moving nbd_get_socket() down. > I was have moved nbd_reclassify_socket up, just like you suggested, but git > don't understanded this very well. But I will find way to get it No , I couldn't do it :( thanks, Guilherme