On Tue, Sep 13, 2022 at 12:17:03PM +0800, ZiyangZhang wrote:
> Define some macros for recovery feature. Especially define a new state:
> UBLK_S_DEV_QUIESCED which implies that ublk_device is quiesced
> and is ready for recovery. This state can be observed by userspace.
>
> UBLK_F_USER_RECOVERY implies that:
> (1) ublk_drv enables recovery feature. It won't let monitor_work to
> automatically abort rqs and release the device.
> (2) With a dying ubq_daemon, ublk_drv ends(aborts) rqs issued to
> userspace(ublksrv) before crash.
> (3) With a dying ubq_daemon, in task work and ublk_queue_rq(),
> ublk_drv requeues rqs.
>
> UBLK_F_USER_RECOVERY_REISSUE implies that:
> (1) everything UBLK_F_USER_RECOVERY implies except
> (2) With a dying ubq_daemon, ublk_drv requeues rqs issued to
> userspace(ublksrv) before crash.
>
> UBLK_F_USER_RECOVERY_REISSUE is designed for backends which:
> (1) tolerates double-writes because ublk_drv may issue the same rq
> twice.
> (2) does not let frontend users get I/O error. such as read-only FS
> and VM backend.
>
> Signed-off-by: ZiyangZhang <ZiyangZhang@xxxxxxxxxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 45 ++++++++++++++++++++++++++++++++++-
> include/uapi/linux/ublk_cmd.h | 7 ++++++
> 2 files changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 0c6db0978ed0..23337bd7c105 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -49,7 +49,9 @@
> /* All UBLK_F_* have to be included into UBLK_F_ALL */
> #define UBLK_F_ALL (UBLK_F_SUPPORT_ZERO_COPY \
> | UBLK_F_URING_CMD_COMP_IN_TASK \
> - | UBLK_F_NEED_GET_DATA)
> + | UBLK_F_NEED_GET_DATA \
> + | UBLK_F_USER_RECOVERY \
> + | UBLK_F_USER_RECOVERY_REISSUE)
>
> /* All UBLK_PARAM_TYPE_* should be included here */
> #define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
> @@ -323,6 +325,47 @@ static inline int ublk_queue_cmd_buf_size(struct ublk_device *ub, int q_id)
> PAGE_SIZE);
> }
>
> +static inline bool ublk_queue_can_use_recovery(
> + struct ublk_queue *ubq)
> +{
> + if (ubq->flags & UBLK_F_USER_RECOVERY)
> + return true;
> + return false;
> +}
> +
> +static inline void ublk_disable_recovery(struct ublk_device *ub)
> +{
> + int i;
> +
> + for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
> + struct ublk_queue *ubq = ublk_get_queue(ub, i);
> +
> + ubq->flags &= ~UBLK_F_USER_RECOVERY;
> + }
> +}
Flags is supposed to not changed, especially ublk_disable_recovery
isn't necessary with my suggestion in the following link:
https://lore.kernel.org/linux-block/YylEjEply6y+bs0B@T590/T/#u
> +
> +static inline bool ublk_can_use_recovery(struct ublk_device *ub)
> +{
> + int i;
> +
> + for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
> + struct ublk_queue *ubq = ublk_get_queue(ub, i);
> +
> + if (!ublk_queue_can_use_recovery(ubq))
> + return false;
> + }
> + return true;
> +}
The above is too tricky, why can't check ub->dev_info &
UBLK_F_USER_RECOVERY directly?
> +
> +static inline bool ublk_queue_can_use_recovery_reissue(
> + struct ublk_queue *ubq)
> +{
> + if (ublk_queue_can_use_recovery(ubq) &&
> + (ubq->flags & UBLK_F_USER_RECOVERY_REISSUE))
> + return true;
> + return false;
> +}
> +
> static void ublk_free_disk(struct gendisk *disk)
> {
> struct ublk_device *ub = disk->private_data;
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index 677edaab2b66..87204c39f1ee 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -17,6 +17,8 @@
> #define UBLK_CMD_STOP_DEV 0x07
> #define UBLK_CMD_SET_PARAMS 0x08
> #define UBLK_CMD_GET_PARAMS 0x09
> +#define UBLK_CMD_START_USER_RECOVERY 0x10
> +#define UBLK_CMD_END_USER_RECOVERY 0x11
>
> /*
> * IO commands, issued by ublk server, and handled by ublk driver.
> @@ -74,9 +76,14 @@
> */
> #define UBLK_F_NEED_GET_DATA (1UL << 2)
>
> +#define UBLK_F_USER_RECOVERY (1UL << 3)
> +
> +#define UBLK_F_USER_RECOVERY_REISSUE (1UL << 4)
The above are two features. I'd suggest to add UBLK_F_USER_RECOVERY
and its implementation first, then add one delta patch for supporting
the new feature of UBLK_F_USER_RECOVERY_REISSUE.
Not only it is more helpful for reviewing, but also easier to understand
the two's difference.
thanks,
Ming
