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Josef Bacik
7bf71ecab1
Since commit "ublk: keep a canceled FETCH round canceling until the server is gone", a device whose FETCH round saw a cancel keeps its queues canceling until the server goes away, but START_DEV and END_USER_RECOVERY still bring it up. Without UBLK_F_USER_RECOVERY, or with UBLK_F_USER_RECOVERY_FAIL_IO, every request of the new disk fails. With UBLK_F_USER_RECOVERY, requests are requeued and never kicked: after START_DEV the partition scan hangs under disk->open_mutex, and after END_USER_RECOVERY every read parks while the command returned 0. The server cannot fetch the canceled commands again, so the device can't serve I/O until it restarts anyway. Return -EBUSY from START_DEV and END_USER_RECOVERY while ub->canceling is set. In ublk_ctrl_start_dev() check it and publish ub->ub_disk in one cancel_mutex section, and have ublk_start_cancel() read the disk in its cancel_mutex section. Today ublk_start_cancel() samples the disk before taking the mutex, so a server dying during its own START_DEV can mark the queues without quiescing a disk START_DEV published in between, with its first I/O past the canceling check. Now either START_DEV sees the cancel, or the cancel sees the disk and quiesces it before marking. The END_USER_RECOVERY check is best effort: the disk exists there, and a cancel after it is the ordinary death of the new server, which ublk_start_cancel() handles by quiescing and marking. Assisted-by: LLM Reviewed-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Ming Lei <tom.leiming@gmail.com> Link: https://patch.msgid.link/20261011063555.1142277-9-tom.leiming@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>