ublk: scan partition in async way #431
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added 3 commits
December 28, 2025 17:35
Implement async partition scan to avoid IO hang when reading partition tables. Similar to nvme_partition_scan_work(), partition scanning is deferred to a work queue to prevent deadlocks. When partition scan happens synchronously during add_disk(), IO errors can cause the partition scan to wait while holding ub->mutex, which can deadlock with other operations that need the mutex. Changes: - Add partition_scan_work to ublk_device structure - Implement ublk_partition_scan_work() to perform async scan - Always suppress sync partition scan during add_disk() - Schedule async work after add_disk() for trusted daemons - Add flush_work() in ublk_stop_dev() before grabbing ub->mutex Reviewed-by: Caleb Sander Mateos <csander@purestorage.com> Reported-by: Yoav Cohen <yoav@nvidia.com> Closes: https://lore.kernel.org/linux-block/DM4PR12MB63280C5637917C071C2F0D65A9A8A@DM4PR12MB6328.namprd12.prod.outlook.com/ Fixes: 71f28f3 ("ublk_drv: add io_uring based userspace block driver") Signed-off-by: Ming Lei <ming.lei@redhat.com>
Add test_generic_15.sh to verify that async partition scan prevents IO hang when reading partition tables. The test creates ublk devices with fault_inject target and very large delay (60s) to simulate blocked partition table reads, then kills the daemon to verify proper state transitions without hanging: 1. Without recovery support: - Create device with fault_inject and 60s delay - Kill daemon while partition scan may be blocked - Verify device transitions to DEAD state 2. With recovery support (-r 1): - Create device with fault_inject, 60s delay, and recovery - Kill daemon while partition scan may be blocked - Verify device transitions to QUIESCED state Before the async partition scan fix, killing the daemon during partition scan would cause deadlock as partition scan held ub->mutex while waiting for IO. With the async fix, partition scan happens in a work function and flush_work() ensures proper synchronization. Add _add_ublk_dev_no_settle() helper function to skip udevadm settle, which would otherwise hang waiting for partition scan events to complete when partition table read is delayed. Signed-off-by: Ming Lei <ming.lei@redhat.com>
Add header dependencies to kublk build rule so that changes to kublk.h, ublk_dep.h, or utils.h trigger a rebuild. Signed-off-by: Ming Lei <ming.lei@redhat.com>
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Upstream branch: d26143b |
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Pull request for series with
subject: ublk: scan partition in async way
version: 2
url: https://patchwork.kernel.org/project/linux-block/list/?series=1035886