[RFC PATCH 7/9] ublk_drv: define macros for recovery feature and check them

ZiyangZhang
2022-08-24T05:49:15Z

Define some macros for recovery feature. Especially define a new state:
UBLK_S_DEV_RECOVERING which implies the ublk_device is recovering.

UBLK_F_USER_RECOVERY implies that:
(1) ublk_drv enables recovery feature. It won't schedule monitor_work to
automatically abort rqs and release the device. Instead, it waits
for user's START_USER_RECOVERY ctrl-cmd.
(2) while re-initing a ubq, ublk_drv ends(aborts) rqs issued to
userspace(ublksrv) before crash.

(3) while re-initing a ubq, ublk_drv requeues rqs dispatched after crash.

UBLK_F_USER_RECOVERY_REISSUE implies that:
(1) everything UBLK_F_USER_RECOVERY implies except
(2) ublk_drv requeues rqs issued to userspace(ublksrv) before crash.

UBLK_F_USER_RECOVERY_REISSUE is designed for backends which:
(1) tolerate double-writes because we may issue the same rq twice.
(2) cannot let frontend users get I/O error, such as a RDONLY system.

For now, we do not allow STOP_DEV while we are in UBLK_S_DEV_RECOVERING.
This means that user must assign a new ubq_daemon for each ubq after
sending START_USER_RECOVERY ctrl-cmd.

Also modify checks on state in START_DEV and SET_PARAMS because now we
have three states.

Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
---
drivers/block/ublk_drv.c | 47 ++++++++++++++++++++++++++++++-----
include/uapi/linux/ublk_cmd.h | 7 ++++++
2 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 4bbd97ccaedf..0ee871fa3f92 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)
@@ -322,6 +324,33 @@ static inline int ublk_queue_cmd_buf_size(struct ublk_device *ub, int q_id)
PAGE_SIZE);
}

+/*
+ * TODO: UBLK_F_USER_RECOVERY should be a flag for device, not for queue,
+ * since "some queues are aborted while others are recovered" is really weird.
+ */
+static inline bool ublk_can_use_recovery(struct ublk_device *ub)
+{
+ struct ublk_queue *ubq = ublk_get_queue(ub, 0);
+
+ if (ubq->flags & UBLK_F_USER_RECOVERY)
+ return true;
+ return false;
+}
+
+/*
+ * TODO: UBLK_F_USER_RECOVERY_REISSUE should be a flag for device, not for queue,
+ * since "some queues are aborted while others are recovered" is really weird.
+ */
+static inline bool ublk_can_use_recovery_reissue(struct ublk_device *ub)
+{
+ struct ublk_queue *ubq = ublk_get_queue(ub, 0);
+
+ if ((ubq->flags & UBLK_F_USER_RECOVERY) &&
+ (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;
@@ -1029,10 +1058,15 @@ static void ublk_stop_dev(struct ublk_device *ub)
{
mutex_lock(&ub->mutex);
/* No gendisk is live. ubq may be ready or not */
- if (ub->dev_info.state == UBLK_S_DEV_DEAD)
+ if (ub->dev_info.state == UBLK_S_DEV_DEAD) {
goto out_cancel_dev;
-
- mod_delayed_work(system_wq, &ub->monitor_work, 0);
+ /* TODO: support stop_dev just after start_recovery */
+ } else if (ub->dev_info.state == UBLK_S_DEV_RECOVERING) {
+ goto out_unlock;
+ /* schedule monitor_work to abort any dying queue */
+ } else {
+ mod_delayed_work(system_wq, &ub->monitor_work, 0);
+ }
pr_devel("%s: Wait for all requests ended...\n", __func__);
blk_mq_freeze_queue(ub->ub_disk->queue);
ub->dev_info.state = UBLK_S_DEV_DEAD;
@@ -1044,6 +1078,7 @@ static void ublk_stop_dev(struct ublk_device *ub)
ub->ub_disk = NULL;
out_cancel_dev:
ublk_cancel_dev(ub);
+ out_unlock:
mutex_unlock(&ub->mutex);
}

@@ -1403,7 +1438,7 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
schedule_delayed_work(&ub->monitor_work, UBLK_DAEMON_MONITOR_PERIOD);

mutex_lock(&ub->mutex);
- if (ub->dev_info.state == UBLK_S_DEV_LIVE ||
+ if (ub->dev_info.state != UBLK_S_DEV_DEAD ||
test_bit(UB_STATE_USED, &ub->state)) {
ret = -EEXIST;
goto out_unlock;
@@ -1746,7 +1781,7 @@ static int ublk_ctrl_set_params(struct io_uring_cmd *cmd)

/* parameters can only be changed when device isn't live */
mutex_lock(&ub->mutex);
- if (ub->dev_info.state == UBLK_S_DEV_LIVE) {
+ if (ub->dev_info.state != UBLK_S_DEV_DEAD) {
ret = -EACCES;
} else if (copy_from_user(&ub->params, argp, ph.len)) {
ret = -EFAULT;
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 677edaab2b66..7f7e6f44cec5 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)
+
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
+#define UBLK_S_DEV_RECOVERING 2

/* shipped via sqe->cmd of io_uring command */
struct ublksrv_ctrl_cmd {
--
2.27.0