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ublk: scan partition in async way

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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: 71f28f3136 ("ublk_drv: add io_uring based userspace block driver")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei
2025-12-23 11:27:40 +08:00
committed by Jens Axboe
parent 04bdb1a04d
commit 7fc4da6a30
1 changed files with 32 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
drivers/block/ublk_drv.c
View File

@@ -237,6 +237,7 @@ struct ublk_device {
bool canceling;
pid_t ublksrv_tgid;
struct delayed_work exit_work;
struct work_struct partition_scan_work;
struct ublk_queue *queues[];
};
@@ -254,6 +255,20 @@ static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
u16 q_id, u16 tag, struct ublk_io *io, size_t offset);
static inline unsigned int ublk_req_build_flags(struct request *req);
static void ublk_partition_scan_work(struct work_struct *work)
{
struct ublk_device *ub =
container_of(work, struct ublk_device, partition_scan_work);
if (WARN_ON_ONCE(!test_and_clear_bit(GD_SUPPRESS_PART_SCAN,
&ub->ub_disk->state)))
return;
mutex_lock(&ub->ub_disk->open_mutex);
bdev_disk_changed(ub->ub_disk, false);
mutex_unlock(&ub->ub_disk->open_mutex);
}
static inline struct ublksrv_io_desc *
ublk_get_iod(const struct ublk_queue *ubq, unsigned tag)
{
@@ -2026,6 +2041,7 @@ static void ublk_stop_dev(struct ublk_device *ub)
mutex_lock(&ub->mutex);
ublk_stop_dev_unlocked(ub);
mutex_unlock(&ub->mutex);
flush_work(&ub->partition_scan_work);
ublk_cancel_dev(ub);
}
@@ -2954,9 +2970,17 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
ublk_apply_params(ub);
/* don't probe partitions if any daemon task is un-trusted */
if (ub->unprivileged_daemons)
set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
/*
* Suppress partition scan to avoid potential IO hang.
*
* If ublk server error occurs during partition scan, the IO may
* wait while holding ub->mutex, which can deadlock with other
* operations that need the mutex. Defer partition scan to async
* work.
* For unprivileged daemons, keep GD_SUPPRESS_PART_SCAN set
* permanently.
*/
set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
ublk_get_device(ub);
ub->dev_info.state = UBLK_S_DEV_LIVE;
@@ -2973,6 +2997,10 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
set_bit(UB_STATE_USED, &ub->state);
/* Schedule async partition scan for trusted daemons */
if (!ub->unprivileged_daemons)
schedule_work(&ub->partition_scan_work);
out_put_cdev:
if (ret) {
ublk_detach_disk(ub);
@@ -3138,6 +3166,7 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
mutex_init(&ub->mutex);
spin_lock_init(&ub->lock);
mutex_init(&ub->cancel_mutex);
INIT_WORK(&ub->partition_scan_work, ublk_partition_scan_work);
ret = ublk_alloc_dev_number(ub, header->dev_id);
if (ret < 0)