[PATCH] ublk: consolidate nr_io_ready and nr_queues_ready

Caleb Sander Mateos
2025-09-08T18:45:45Z

ublk_mark_io_ready() tracks whether all the ublk_device's I/Os have been
fetched by incrementing ublk_queue's nr_io_ready count and incrementing
ublk_device's nr_queues_ready count if the whole queue is ready.
Simplify the logic by just tracking the total number of fetched I/Os on
each ublk_device. When this count reaches nr_hw_queues * queue_depth,
the ublk_device is ready to receive I/O.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
drivers/block/ublk_drv.c | 28 ++++++++++++----------------
1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 3cf6d344d1c0..aa64f530d5e9 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -199,11 +199,10 @@ struct ublk_queue {
struct ublksrv_io_desc *io_cmd_buf;

bool force_abort;
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;
struct ublk_io ios[];
};

@@ -232,11 +231,11 @@ struct ublk_device {
struct mm_struct *mm;

struct ublk_params params;

struct completion completion;
- unsigned int nr_queues_ready;
+ u32 nr_io_ready;
bool unprivileged_daemons;
struct mutex cancel_mutex;
bool canceling;
pid_t ublksrv_tgid;
};
@@ -1497,13 +1496,10 @@ static const struct blk_mq_ops ublk_mq_ops = {

static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
{
int i;

- /* All old ioucmds have to be completed */
- ubq->nr_io_ready = 0;
-
for (i = 0; i < ubq->q_depth; i++) {
struct ublk_io *io = &ubq->ios[i];

/*
* UBLK_IO_FLAG_CANCELED is kept for avoiding to touch
@@ -1548,11 +1544,11 @@ static void ublk_reset_ch_dev(struct ublk_device *ub)
for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
ublk_queue_reinit(ub, ublk_get_queue(ub, i));

/* set to NULL, otherwise new tasks cannot mmap io_cmd_buf */
ub->mm = NULL;
- ub->nr_queues_ready = 0;
+ ub->nr_io_ready = 0;
ub->unprivileged_daemons = false;
ub->ublksrv_tgid = -1;
}

static struct gendisk *ublk_get_disk(struct ublk_device *ub)
@@ -1846,13 +1842,15 @@ static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd,

WARN_ON_ONCE(io->cmd != cmd);
ublk_cancel_cmd(ubq, pdu->tag, issue_flags);
}

-static inline bool ublk_queue_ready(struct ublk_queue *ubq)
+static inline bool ublk_dev_ready(const struct ublk_device *ub)
{
- return ubq->nr_io_ready == ubq->q_depth;
+ u32 total = (u32)ub->dev_info.nr_hw_queues * ub->dev_info.queue_depth;
+
+ return ub->nr_io_ready == total;
}

static void ublk_cancel_queue(struct ublk_queue *ubq)
{
int i;
@@ -1972,20 +1970,18 @@ static void ublk_reset_io_flags(struct ublk_device *ub)
ublk_set_canceling(ub, false);
mutex_unlock(&ub->cancel_mutex);
}

/* device can only be started after all IOs are ready */
-static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
+static void ublk_mark_io_ready(struct ublk_device *ub)
__must_hold(&ub->mutex)
{
- ubq->nr_io_ready++;
- if (ublk_queue_ready(ubq))
- ub->nr_queues_ready++;
if (!ub->unprivileged_daemons && !capable(CAP_SYS_ADMIN))
ub->unprivileged_daemons = true;

- if (ub->nr_queues_ready == ub->dev_info.nr_hw_queues) {
+ ub->nr_io_ready++;
+ if (ublk_dev_ready(ub)) {
/* now we are ready for handling ublk io request */
ublk_reset_io_flags(ub);
complete_all(&ub->completion);
}
}
@@ -2187,12 +2183,12 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
* When handling FETCH command for setting up ublk uring queue,
* ub->mutex is the innermost lock, and we won't block for handling
* FETCH, so it is fine even for IO_URING_F_NONBLOCK.
*/
mutex_lock(&ub->mutex);
- /* UBLK_IO_FETCH_REQ is only allowed before queue is setup */
- if (ublk_queue_ready(ubq)) {
+ /* UBLK_IO_FETCH_REQ is only allowed before dev is setup */
+ if (ublk_dev_ready(ub)) {
ret = -EBUSY;
goto out;
}

/* allow each command to be FETCHed at most once */
@@ -2207,11 +2203,11 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
ret = ublk_config_io_buf(ubq, io, cmd, buf_addr, NULL);
if (ret)
goto out;

WRITE_ONCE(io->task, get_task_struct(current));
- ublk_mark_io_ready(ub, ubq);
+ ublk_mark_io_ready(ub);
out:
mutex_unlock(&ub->mutex);
return ret;
}

--
2.45.2