[PATCH 2/2] block: loop: delete partitions after clearing & changing fd

[Ming Lei <ming.lei@xxxxxxxxxx>]

After clearing fd or changing fd, we have to delete old partitions,
otherwise they may become ghost partitions.

Fix this issue by clearing GENHD_FL_NO_PART_SCAN during calling
bdev_disk_changed() which won't drop old partitions if GENHD_FL_NO_PART_SCAN
isn't set.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 drivers/block/loop.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0e08468b9ce0..cf71a1bbcd45 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -650,17 +650,26 @@ static inline void loop_update_dio(struct loop_device *lo)
 }
 
 static void loop_reread_partitions(struct loop_device *lo,
-				   struct block_device *bdev, bool locked)
+				   struct block_device *bdev, bool locked,
+				   bool force_scan)
 {
 	int rc;
+	bool no_scan;
 
-	if (locked) {
-		rc = bdev_disk_changed(bdev, false);
-	} else {
+	if (!locked)
 		mutex_lock(&bdev->bd_mutex);
-		rc = bdev_disk_changed(bdev, false);
+
+	no_scan = lo->lo_disk->flags & GENHD_FL_NO_PART_SCAN;
+	if (force_scan && no_scan)
+		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
+
+	rc = bdev_disk_changed(bdev, false);
+
+	if (force_scan && no_scan)
+		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
+
+	if (!locked)
 		mutex_unlock(&bdev->bd_mutex);
-	}
 	if (rc)
 		pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
 			__func__, lo->lo_number, lo->lo_file_name, rc);
@@ -758,7 +767,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	 */
 	fput(old_file);
 	if (partscan)
-		loop_reread_partitions(lo, bdev, false);
+		loop_reread_partitions(lo, bdev, false, true);
 	return 0;
 
 out_err:
@@ -1183,7 +1192,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	bdgrab(bdev);
 	mutex_unlock(&loop_ctl_mutex);
 	if (partscan)
-		loop_reread_partitions(lo, bdev, false);
+		loop_reread_partitions(lo, bdev, false, false);
 	if (claimed_bdev)
 		bd_abort_claiming(bdev, claimed_bdev, loop_configure);
 	return 0;
@@ -1274,7 +1283,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 		 * must be at least one and it can only become zero when the
 		 * current holder is released.
 		 */
-		loop_reread_partitions(lo, bdev, release);
+		loop_reread_partitions(lo, bdev, release, true);
 	}
 
 	/*
@@ -1415,7 +1424,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 out_unlock:
 	mutex_unlock(&loop_ctl_mutex);
 	if (partscan)
-		loop_reread_partitions(lo, bdev, false);
+		loop_reread_partitions(lo, bdev, false, false);
 
 	return err;
 }
-- 
2.25.2