[PATCH V2 2/9] ublk: add UBLK_F_NO_AUTO_PART_SCAN feature flag

[Ming Lei <ming.lei@redhat.com>]

Add a new feature flag UBLK_F_NO_AUTO_PART_SCAN to allow users to suppress
automatic partition scanning when starting a ublk device.

This is useful for some cases in which user don't want to scan
partitions.

Users still can manually trigger partition scanning later when appropriate
using standard tools (e.g., partprobe, blockdev --rereadpt).

Reported-by: Yoav Cohen <yoav@nvidia.com>
Link: https://lore.kernel.org/linux-block/DM4PR12MB63280C5637917C071C2F0D65A9A8A@DM4PR12MB6328.namprd12.prod.outlook.com/
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/block/ublk_drv.c      | 14 ++++++++++----
 include/uapi/linux/ublk_cmd.h |  3 +++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 94470a2ec05e..aa9ea39249b0 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -80,7 +80,8 @@
 		| UBLK_F_BUF_REG_OFF_DAEMON \
 		| (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) ? UBLK_F_INTEGRITY : 0) \
 		| UBLK_F_SAFE_STOP_DEV \
-		| UBLK_F_BATCH_IO)
+		| UBLK_F_BATCH_IO \
+		| UBLK_F_NO_AUTO_PART_SCAN)
 
 #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
 		| UBLK_F_USER_RECOVERY_REISSUE \
@@ -4430,9 +4431,14 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
 
 	set_bit(UB_STATE_USED, &ub->state);
 
-	/* Schedule async partition scan for trusted daemons */
-	if (!ub->unprivileged_daemons)
-		schedule_work(&ub->partition_scan_work);
+	/* Skip partition scan if disabled by user */
+	if (ub->dev_info.flags & UBLK_F_NO_AUTO_PART_SCAN) {
+		clear_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
+	} else {
+		/* Schedule async partition scan for trusted daemons */
+		if (!ub->unprivileged_daemons)
+			schedule_work(&ub->partition_scan_work);
+	}
 
 out_put_cdev:
 	if (ret) {
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 743d31491387..a88876756805 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -367,6 +367,9 @@
  */
 #define UBLK_F_SAFE_STOP_DEV	(1ULL << 17)
 
+/* Disable automatic partition scanning when device is started */
+#define UBLK_F_NO_AUTO_PART_SCAN (1ULL << 18)
+
 /* device state */
 #define UBLK_S_DEV_DEAD	0
 #define UBLK_S_DEV_LIVE	1
-- 
2.47.0