[PATCH V2 4/6] ublk_drv: add device parameter UBLK_PARAM_TYPE_DEVT

Ming Lei
2022-11-24T03:06:36Z

Userspace side only knows device ID, but the associated path of ublkc* and
ublkb* could be changed by udev, and that depends on userspace's policy, so
add parameter of UBLK_PARAM_TYPE_DEVT for retrieving major/minor of the
ublkc* and ublkb*, then user may figure out major/minor of the ublk disks
he/she owns. With major/minor, it is easy to find the device node path.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/block/ublk_drv.c | 24 +++++++++++++++++++++++-
include/uapi/linux/ublk_cmd.h | 13 +++++++++++++
2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 9d1578384cba..04a28a2f2e1f 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -54,7 +54,8 @@
| 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)
+#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | \
+ UBLK_PARAM_TYPE_DISCARD | UBLK_PARAM_TYPE_DEVT)

struct ublk_rq_data {
struct llist_node node;
@@ -255,6 +256,10 @@ static int ublk_validate_params(const struct ublk_device *ub)
return -EINVAL;
}

+ /* dev_t is read-only */
+ if (ub->params.types & UBLK_PARAM_TYPE_DEVT)
+ WARN_ON_ONCE(1);
+
return 0;
}

@@ -1777,6 +1782,22 @@ static int ublk_ctrl_get_dev_info(struct ublk_device *ub,
return 0;
}

+/* TYPE_DEVT is readonly, so fill it up before returning to userspace */
+static void ublk_ctrl_fill_params_devt(struct ublk_device *ub)
+{
+ ub->params.devt.char_major = MAJOR(ub->cdev_dev.devt);
+ ub->params.devt.char_minor = MINOR(ub->cdev_dev.devt);
+
+ if (ub->ub_disk) {
+ ub->params.devt.disk_major = MAJOR(disk_devt(ub->ub_disk));
+ ub->params.devt.disk_minor = MINOR(disk_devt(ub->ub_disk));
+ } else {
+ ub->params.devt.disk_major = 0;
+ ub->params.devt.disk_minor = 0;
+ }
+ ub->params.types |= UBLK_PARAM_TYPE_DEVT;
+}
+
static int ublk_ctrl_get_params(struct ublk_device *ub,
struct io_uring_cmd *cmd)
{
@@ -1798,6 +1819,7 @@ static int ublk_ctrl_get_params(struct ublk_device *ub,
ph.len = sizeof(struct ublk_params);

mutex_lock(&ub->mutex);
+ ublk_ctrl_fill_params_devt(ub);
if (copy_to_user(argp, &ub->params, ph.len))
ret = -EFAULT;
else
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 8f88e3a29998..4e38b9aa0293 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -214,6 +214,17 @@ struct ublk_param_discard {
__u16 reserved0;
};

+/*
+ * read-only, can't set via UBLK_CMD_SET_PARAMS, disk_devt is available
+ * after device is started
+ */
+struct ublk_param_devt {
+ __u32 char_major;
+ __u32 char_minor;
+ __u32 disk_major;
+ __u32 disk_minor;
+};
+
struct ublk_params {
/*
* Total length of parameters, userspace has to set 'len' for both
@@ -224,10 +235,12 @@ struct ublk_params {
__u32 len;
#define UBLK_PARAM_TYPE_BASIC (1 << 0)
#define UBLK_PARAM_TYPE_DISCARD (1 << 1)
+#define UBLK_PARAM_TYPE_DEVT (1 << 2)
__u32 types; /* types of parameter included */

struct ublk_param_basic basic;
struct ublk_param_discard discard;
+ struct ublk_param_devt devt;
};

#endif
--
2.31.1