Re: [PATCH v3 4/5] ublk: support device recovery without I/O queueing

[Ming Lei <ming.lei@redhat.com>]

On Wed, Oct 02, 2024 at 04:09:48PM -0600, Uday Shankar wrote:
> ublk currently supports the following behaviors on ublk server exit:
> 
> A: outstanding I/Os get errors, subsequently issued I/Os get errors
> B: outstanding I/Os get errors, subsequently issued I/Os queue
> C: outstanding I/Os get reissued, subsequently issued I/Os queue
> 
> and the following behaviors for recovery of preexisting block devices by
> a future incarnation of the ublk server:
> 
> 1: ublk devices stopped on ublk server exit (no recovery possible)
> 2: ublk devices are recoverable using start/end_recovery commands
> 
> The userspace interface allows selection of combinations of these
> behaviors using flags specified at device creation time, namely:
> 
> default behavior: A + 1
> UBLK_F_USER_RECOVERY: B + 2
> UBLK_F_USER_RECOVERY|UBLK_F_USER_RECOVERY_REISSUE: C + 2
> 
> The behavior A + 2 is currently unsupported. Add support for this
> behavior under the new flag combination
> UBLK_F_USER_RECOVERY|UBLK_F_USER_RECOVERY_FAIL_IO.
> 
> Signed-off-by: Uday Shankar <ushankar@purestorage.com>
> ---
> Changes since v2 (https://lore.kernel.org/linux-block/20240917002155.2044225-5-ushankar@purestorage.com/):
> - Clean up logic in ublk_ctrl_end_recovery
> 
>  drivers/block/ublk_drv.c      | 78 ++++++++++++++++++++++++++++-------
>  include/uapi/linux/ublk_cmd.h | 18 ++++++++
>  2 files changed, 81 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index d5edef7bde43..f2a05dcbc58b 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -60,10 +60,12 @@
>  		| UBLK_F_UNPRIVILEGED_DEV \
>  		| UBLK_F_CMD_IOCTL_ENCODE \
>  		| UBLK_F_USER_COPY \
> -		| UBLK_F_ZONED)
> +		| UBLK_F_ZONED \
> +		| UBLK_F_USER_RECOVERY_FAIL_IO)
>  
>  #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
> -		| UBLK_F_USER_RECOVERY_REISSUE)
> +		| UBLK_F_USER_RECOVERY_REISSUE \
> +		| UBLK_F_USER_RECOVERY_FAIL_IO)
>  
>  /* All UBLK_PARAM_TYPE_* should be included here */
>  #define UBLK_PARAM_TYPE_ALL                                \
> @@ -146,6 +148,7 @@ struct ublk_queue {
>  	bool force_abort;
>  	bool timeout;
>  	bool canceling;
> +	bool fail_io; /* copy of dev->state == UBLK_S_DEV_FAIL_IO */
>  	unsigned short nr_io_ready;	/* how many ios setup */
>  	spinlock_t		cancel_lock;
>  	struct ublk_device *dev;
> @@ -690,7 +693,8 @@ static inline bool ublk_nosrv_should_reissue_outstanding(struct ublk_device *ub)
>   */
>  static inline bool ublk_nosrv_dev_should_queue_io(struct ublk_device *ub)
>  {
> -	return ub->dev_info.flags & UBLK_F_USER_RECOVERY;
> +	return (ub->dev_info.flags & UBLK_F_USER_RECOVERY) &&
> +	       !(ub->dev_info.flags & UBLK_F_USER_RECOVERY_FAIL_IO);
>  }
>  
>  /*
> @@ -700,7 +704,8 @@ static inline bool ublk_nosrv_dev_should_queue_io(struct ublk_device *ub)
>   */
>  static inline bool ublk_nosrv_should_queue_io(struct ublk_queue *ubq)
>  {
> -	return ubq->flags & UBLK_F_USER_RECOVERY;
> +	return (ubq->flags & UBLK_F_USER_RECOVERY) &&
> +	       !(ubq->flags & UBLK_F_USER_RECOVERY_FAIL_IO);
>  }
>  
>  /*
> @@ -714,6 +719,12 @@ static inline bool ublk_nosrv_should_stop_dev(struct ublk_device *ub)
>  	return !(ub->dev_info.flags & UBLK_F_USER_RECOVERY);
>  }
>  
> +static inline bool ublk_dev_in_recoverable_state(struct ublk_device *ub)
> +{
> +	return ub->dev_info.state == UBLK_S_DEV_QUIESCED ||
> +	       ub->dev_info.state == UBLK_S_DEV_FAIL_IO;
> +}
> +
>  static void ublk_free_disk(struct gendisk *disk)
>  {
>  	struct ublk_device *ub = disk->private_data;
> @@ -1275,6 +1286,10 @@ static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx,
>  	struct request *rq = bd->rq;
>  	blk_status_t res;
>  
> +	if (unlikely(ubq->fail_io)) {
> +		return BLK_STS_TARGET;
> +	}
> +
>  	/* fill iod to slot in io cmd buffer */
>  	res = ublk_setup_iod(ubq, rq);
>  	if (unlikely(res != BLK_STS_OK))
> @@ -1625,6 +1640,7 @@ static void ublk_nosrv_work(struct work_struct *work)
>  {
>  	struct ublk_device *ub =
>  		container_of(work, struct ublk_device, nosrv_work);
> +	int i;
>  
>  	if (ublk_nosrv_should_stop_dev(ub)) {
>  		ublk_stop_dev(ub);
> @@ -1634,7 +1650,18 @@ static void ublk_nosrv_work(struct work_struct *work)
>  	mutex_lock(&ub->mutex);
>  	if (ub->dev_info.state != UBLK_S_DEV_LIVE)
>  		goto unlock;
> -	__ublk_quiesce_dev(ub);
> +
> +	if (ublk_nosrv_dev_should_queue_io(ub)) {
> +		__ublk_quiesce_dev(ub);
> +	} else {
> +		blk_mq_quiesce_queue(ub->ub_disk->queue);
> +		for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
> +			ublk_get_queue(ub, i)->fail_io = true;
> +		}
> +		blk_mq_unquiesce_queue(ub->ub_disk->queue);
> +		ub->dev_info.state = UBLK_S_DEV_FAIL_IO;

The above state update should be moved before blk_mq_unquiesce_queue().

Otherwise, this patch is fine.

Thanks, 
Ming