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Fri, 06 Nov 2026 06:48:57 -0800 (PST) Received: from fedora-laptop ([120.229.31.43]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b25e4879adsm7528337c88.6.2026.11.06.06.48.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2026 06:48:56 -0800 (PST) Date: Fri, 6 Nov 2026 08:48:52 -0600 From: Ming Lei To: socketpair@gmail.com Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] ublk: publish a new device by its id only once it is set up Message-ID: References: <20261105-ublk-del-gendisk-hang-v1-0-913a91a4314d@gmail.com> <20261105-ublk-del-gendisk-hang-v1-1-913a91a4314d@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105-ublk-del-gendisk-hang-v1-1-913a91a4314d@gmail.com> On Thu, Nov 05, 2026 at 12:25:05AM +0500, Mark Korenberg via B4 Relay wrote: > From: Mark Korenberg > > ADD_DEV stores the device in ublk_index_idr when it allocates the id, > and control commands find it there as soon as ublk_add_chdev() has > initialized its struct device, before the char device is added. If > dev_set_name() or cdev_device_add() then fails, ublk_add_chdev() drops > the initial reference to free the device. A DEL_DEV that found the > device meanwhile waits for ublk_ctl_mutex, then calls ublk_remove(): > cdev_device_del() of a device that was never added, and a second put of > the initial reference, which frees the device under the callers still > holding references. > > Reserve the id with a NULL entry, which idr_find() and the idr iterators > skip, and store the device once ublk_add_chdev() succeeded. > > Fixes: 71f28f3136af ("ublk_drv: add io_uring based userspace block driver") > Signed-off-by: Mark Korenberg Reviewed-by: Ming Lei Thanks, Ming