6.18-stable review patch. If anyone has any objections, please let me know.
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From: Ming Lei ming.lei@redhat.com
[ Upstream commit 7fc4da6a304bdcd3de14fc946dc2c19437a9cc5a ]
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@D... Fixes: 71f28f3136af ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/ublk_drv.c | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 796035891888..23aba73d24dc 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -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) { @@ -2092,6 +2107,7 @@ 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); }
@@ -3023,9 +3039,17 @@ 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; @@ -3042,6 +3066,10 @@ 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); @@ -3207,6 +3235,7 @@ 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)