ublk_drv: add SET_PARAMS/GET_PARAMS control command

Add two commands to set/get parameters generically.

One important goal of ublk is to provide generic framework for making
block device by userspace flexibly.

As one generic block device, there are still lots of block parameters,
such as max_sectors, write_cache/fua, discard related limits,
zoned parameters, ...., so this patch starts to add generic mechanism
for set/get device parameters.

Both generic block parameters(all kinds of queue settings) and ublk
feature parameters can be covered with this way, then it becomes quite
easy to extend in future.

Add two parameter types are used so far: basic(covers basic queue setting
and misc settings which can't be grouped easily) and discard, basic type
must be set, and discard type becomes optional now

This way provides mechanism to simulate any kind of generic block device
from userspace easily, from both block queue setting viewpoint or ublk
feature viewpoint.

The style of putting all parameters together is suggested by Christoph.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220730092750.1118167-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 187 insertions, 18 deletions

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index ae98e81b21ce..20ad83b25318 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -49,6 +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)
 
+/* All UBLK_PARAM_TYPE_* should be included here */
+#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
+
 struct ublk_rq_data {
 	struct callback_head work;
 };
@@ -137,6 +140,8 @@ struct ublk_device {
 	spinlock_t		mm_lock;
 	struct mm_struct	*mm;
 
+	struct ublk_params	params;
+
 	struct completion	completion;
 	unsigned int		nr_queues_ready;
 	atomic_t		nr_aborted_queues;
@@ -149,6 +154,12 @@ struct ublk_device {
 	struct work_struct	stop_work;
 };
 
+/* header of ublk_params */
+struct ublk_params_header {
+	__u32	len;
+	__u32	types;
+};
+
 static dev_t ublk_chr_devt;
 static struct class *ublk_chr_class;
 
@@ -160,6 +171,91 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
 
 static struct miscdevice ublk_misc;
 
+static void ublk_dev_param_basic_apply(struct ublk_device *ub)
+{
+	struct request_queue *q = ub->ub_disk->queue;
+	const struct ublk_param_basic *p = &ub->params.basic;
+
+	blk_queue_logical_block_size(q, 1 << p->logical_bs_shift);
+	blk_queue_physical_block_size(q, 1 << p->physical_bs_shift);
+	blk_queue_io_min(q, 1 << p->io_min_shift);
+	blk_queue_io_opt(q, 1 << p->io_opt_shift);
+
+	blk_queue_write_cache(q, p->attrs & UBLK_ATTR_VOLATILE_CACHE,
+			p->attrs & UBLK_ATTR_FUA);
+	if (p->attrs & UBLK_ATTR_ROTATIONAL)
+		blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
+	else
+		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
+
+	blk_queue_max_hw_sectors(q, p->max_sectors);
+	blk_queue_chunk_sectors(q, p->chunk_sectors);
+	blk_queue_virt_boundary(q, p->virt_boundary_mask);
+
+	if (p->attrs & UBLK_ATTR_READ_ONLY)
+		set_disk_ro(ub->ub_disk, true);
+
+	set_capacity(ub->ub_disk, p->dev_sectors);
+}
+
+static void ublk_dev_param_discard_apply(struct ublk_device *ub)
+{
+	struct request_queue *q = ub->ub_disk->queue;
+	const struct ublk_param_discard *p = &ub->params.discard;
+
+	q->limits.discard_alignment = p->discard_alignment;
+	q->limits.discard_granularity = p->discard_granularity;
+	blk_queue_max_discard_sectors(q, p->max_discard_sectors);
+	blk_queue_max_write_zeroes_sectors(q,
+			p->max_write_zeroes_sectors);
+	blk_queue_max_discard_segments(q, p->max_discard_segments);
+}
+
+static int ublk_validate_params(const struct ublk_device *ub)
+{
+	/* basic param is the only one which must be set */
+	if (ub->params.types & UBLK_PARAM_TYPE_BASIC) {
+		const struct ublk_param_basic *p = &ub->params.basic;
+
+		if (p->logical_bs_shift > PAGE_SHIFT)
+			return -EINVAL;
+
+		if (p->logical_bs_shift > p->physical_bs_shift)
+			return -EINVAL;
+
+		if (p->max_sectors > (ub->dev_info.rq_max_blocks <<
+					(ub->bs_shift - 9)))
+			return -EINVAL;
+	} else
+		return -EINVAL;
+
+	if (ub->params.types & UBLK_PARAM_TYPE_DISCARD) {
+		const struct ublk_param_discard *p = &ub->params.discard;
+
+		/* So far, only support single segment discard */
+		if (p->max_discard_sectors && p->max_discard_segments != 1)
+			return -EINVAL;
+
+		if (!p->discard_granularity)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int ublk_apply_params(struct ublk_device *ub)
+{
+	if (!(ub->params.types & UBLK_PARAM_TYPE_BASIC))
+		return -EINVAL;
+
+	ublk_dev_param_basic_apply(ub);
+
+	if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
+		ublk_dev_param_discard_apply(ub);
+
+	return 0;
+}
+
 static inline bool ublk_can_use_task_work(const struct ublk_queue *ubq)
 {
 	if (IS_BUILTIN(CONFIG_BLK_DEV_UBLK) &&
@@ -1138,7 +1234,6 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
 {
 	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
 	int ublksrv_pid = (int)header->data[0];
-	unsigned long dev_blocks = header->data[1];
 	struct ublk_device *ub;
 	struct gendisk *disk;
 	int ret = -EINVAL;
@@ -1161,10 +1256,6 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
 		goto out_unlock;
 	}
 
-	/* We may get disk size updated */
-	if (dev_blocks)
-		ub->dev_info.dev_blocks = dev_blocks;
-
 	disk = blk_mq_alloc_disk(&ub->tag_set, ub);
 	if (IS_ERR(disk)) {
 		ret = PTR_ERR(disk);
@@ -1174,19 +1265,13 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
 	disk->fops = &ub_fops;
 	disk->private_data = ub;
 
-	blk_queue_logical_block_size(disk->queue, ub->dev_info.block_size);
-	blk_queue_physical_block_size(disk->queue, ub->dev_info.block_size);
-	blk_queue_io_min(disk->queue, ub->dev_info.block_size);
-	blk_queue_max_hw_sectors(disk->queue,
-		ub->dev_info.rq_max_blocks << (ub->bs_shift - 9));
-	disk->queue->limits.discard_granularity = PAGE_SIZE;
-	blk_queue_max_discard_sectors(disk->queue, UINT_MAX >> 9);
-	blk_queue_max_write_zeroes_sectors(disk->queue, UINT_MAX >> 9);
-
-	set_capacity(disk, ub->dev_info.dev_blocks << (ub->bs_shift - 9));
-
 	ub->dev_info.ublksrv_pid = ublksrv_pid;
 	ub->ub_disk = disk;
+
+	ret = ublk_apply_params(ub);
+	if (ret)
+		goto out_put_disk;
+
 	get_device(&ub->cdev_dev);
 	ret = add_disk(disk);
 	if (ret) {
@@ -1195,11 +1280,13 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
 		 * called in case of add_disk failure.
 		 */
 		ublk_put_device(ub);
-		put_disk(disk);
-		goto out_unlock;
+		goto out_put_disk;
 	}
 	set_bit(UB_STATE_USED, &ub->state);
 	ub->dev_info.state = UBLK_S_DEV_LIVE;
+out_put_disk:
+	if (ret)
+		put_disk(disk);
 out_unlock:
 	mutex_unlock(&ub->mutex);
 	ublk_put_device(ub);
@@ -1447,6 +1534,82 @@ static int ublk_ctrl_get_dev_info(struct io_uring_cmd *cmd)
 	return ret;
 }
 
+static int ublk_ctrl_get_params(struct io_uring_cmd *cmd)
+{
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	void __user *argp = (void __user *)(unsigned long)header->addr;
+	struct ublk_params_header ph;
+	struct ublk_device *ub;
+	int ret;
+
+	if (header->len <= sizeof(ph) || !header->addr)
+		return -EINVAL;
+
+	if (copy_from_user(&ph, argp, sizeof(ph)))
+		return -EFAULT;
+
+	if (ph.len > header->len || !ph.len)
+		return -EINVAL;
+
+	if (ph.len > sizeof(struct ublk_params))
+		ph.len = sizeof(struct ublk_params);
+
+	ub = ublk_get_device_from_id(header->dev_id);
+	if (!ub)
+		return -EINVAL;
+
+	mutex_lock(&ub->mutex);
+	if (copy_to_user(argp, &ub->params, ph.len))
+		ret = -EFAULT;
+	else
+		ret = 0;
+	mutex_unlock(&ub->mutex);
+
+	ublk_put_device(ub);
+	return ret;
+}
+
+static int ublk_ctrl_set_params(struct io_uring_cmd *cmd)
+{
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	void __user *argp = (void __user *)(unsigned long)header->addr;
+	struct ublk_params_header ph;
+	struct ublk_device *ub;
+	int ret = -EFAULT;
+
+	if (header->len <= sizeof(ph) || !header->addr)
+		return -EINVAL;
+
+	if (copy_from_user(&ph, argp, sizeof(ph)))
+		return -EFAULT;
+
+	if (ph.len > header->len || !ph.len || !ph.types)
+		return -EINVAL;
+
+	if (ph.len > sizeof(struct ublk_params))
+		ph.len = sizeof(struct ublk_params);
+
+	ub = ublk_get_device_from_id(header->dev_id);
+	if (!ub)
+		return -EINVAL;
+
+	/* parameters can only be changed when device isn't live */
+	mutex_lock(&ub->mutex);
+	if (ub->dev_info.state == UBLK_S_DEV_LIVE) {
+		ret = -EACCES;
+	} else if (copy_from_user(&ub->params, argp, ph.len)) {
+		ret = -EFAULT;
+	} else {
+		/* clear all we don't support yet */
+		ub->params.types &= UBLK_PARAM_TYPE_ALL;
+		ret = ublk_validate_params(ub);
+	}
+	mutex_unlock(&ub->mutex);
+	ublk_put_device(ub);
+
+	return ret;
+}
+
 static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
@@ -1482,6 +1645,12 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
 	case UBLK_CMD_GET_QUEUE_AFFINITY:
 		ret = ublk_ctrl_get_queue_affinity(cmd);
 		break;
+	case UBLK_CMD_GET_PARAMS:
+		ret = ublk_ctrl_get_params(cmd);
+		break;
+	case UBLK_CMD_SET_PARAMS:
+		ret = ublk_ctrl_set_params(cmd);
+		break;
 	default:
 		break;
 	}