Re: [PATCH] block: Do not reread partition table on exclusively open device

[Christoph Hellwig <hch@infradead.org>]

It might be easier to just move the check into blkdev_get_whole,
which also ensures that non-excluisve openers don't cause a partition
scan while someone else has the device exclusively open.

diff --git a/block/bdev.c b/block/bdev.c
index edc110d90df404..a831b6c9c627d7 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -666,25 +666,28 @@ static void blkdev_flush_mapping(struct block_device *bdev)
 static int blkdev_get_whole(struct block_device *bdev, fmode_t mode)
 {
 	struct gendisk *disk = bdev->bd_disk;
-	int ret;
+	int ret = 0;
 
-	if (disk->fops->open) {
+	if (disk->fops->open)
 		ret = disk->fops->open(bdev, mode);
-		if (ret) {
-			/* avoid ghost partitions on a removed medium */
-			if (ret == -ENOMEDIUM &&
-			     test_bit(GD_NEED_PART_SCAN, &disk->state))
-				bdev_disk_changed(disk, true);
+
+	if (ret) {
+		/* avoid ghost partitions on a removed medium */
+		if (ret != -ENOMEDIUM)
 			return ret;
-		}
+	} else {
+		if (!atomic_read(&bdev->bd_openers))
+			set_init_blocksize(bdev);
+		atomic_inc(&bdev->bd_openers);
 	}
 
-	if (!atomic_read(&bdev->bd_openers))
-		set_init_blocksize(bdev);
-	if (test_bit(GD_NEED_PART_SCAN, &disk->state))
+	/*
+	 * Skip the partition scan if someone else has the device exclusively
+	 * open.
+	 */
+	if (test_bit(GD_NEED_PART_SCAN, &disk->state) && !bdev->bd_holder)
 		bdev_disk_changed(disk, false);
-	atomic_inc(&bdev->bd_openers);
-	return 0;
+	return ret;
 }
 
 static void blkdev_put_whole(struct block_device *bdev, fmode_t mode)
diff --git a/block/genhd.c b/block/genhd.c
index 23cf83b3331cde..4a7b1b8b9efdb5 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -366,9 +366,6 @@ int disk_scan_partitions(struct gendisk *disk, fmode_t mode, void *owner)
 		return -EINVAL;
 	if (disk->open_partitions)
 		return -EBUSY;
-	/* Someone else has bdev exclusively open? */
-	if (disk->part0->bd_holder && disk->part0->bd_holder != owner)
-		return -EBUSY;
 
 	set_bit(GD_NEED_PART_SCAN, &disk->state);
 	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL);