block: remove ->bd_contains

Now that each hd_struct has a reference to the corresponding
block_device, there is no need for the bd_contains pointer.  Add
a bdev_whole() helper to look up the whole device block_device
struture instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1088,7 +1088,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	 * here to avoid changing device under exclusive owner.
 	 */
 	if (!(mode & FMODE_EXCL)) {
-		claimed_bdev = bdev->bd_contains;
+		claimed_bdev = bdev_whole(bdev);
 		error = bd_prepare_to_claim(bdev, claimed_bdev, loop_configure);
 		if (error)
 			goto out_putf;

drivers/scsi/scsicam.c

@@ -32,7 +32,7 @@
  */
 unsigned char *scsi_bios_ptable(struct block_device *dev)
 {
-	struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;
+	struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping;
 	unsigned char *res = NULL;
 	struct page *page;
 

fs/block_dev.c

@@ -119,7 +119,7 @@ int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
 	 * under live filesystem.
 	 */
 	if (!(mode & FMODE_EXCL)) {
-		claimed_bdev = bdev->bd_contains;
+		claimed_bdev = bdev_whole(bdev);
 		err = bd_prepare_to_claim(bdev, claimed_bdev,
 					  truncate_bdev_range);
 		if (err)
@@ -880,7 +880,6 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
 	spin_lock_init(&bdev->bd_size_lock);
 	bdev->bd_disk = disk;
 	bdev->bd_partno = partno;
-	bdev->bd_contains = NULL;
 	bdev->bd_super = NULL;
 	bdev->bd_inode = inode;
 	bdev->bd_part_count = 0;
@@ -1347,9 +1346,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
 	int ret;
 
 	if (!bdev->bd_openers) {
-		bdev->bd_contains = bdev;
-
-		if (!bdev->bd_partno) {
+		if (!bdev_is_partition(bdev)) {
 			ret = -ENXIO;
 			bdev->bd_part = disk_get_part(disk, 0);
 			if (!bdev->bd_part)
@@ -1389,7 +1386,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
 			whole->bd_part_count++;
 			mutex_unlock(&whole->bd_mutex);
 
-			bdev->bd_contains = whole;
 			bdev->bd_part = disk_get_part(disk, bdev->bd_partno);
 			if (!(disk->flags & GENHD_FL_UP) ||
 			    !bdev->bd_part || !bdev->bd_part->nr_sects) {
@@ -1405,7 +1401,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
 		if (bdev->bd_bdi == &noop_backing_dev_info)
 			bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info);
 	} else {
-		if (bdev->bd_contains == bdev) {
+		if (!bdev_is_partition(bdev)) {
 			ret = 0;
 			if (bdev->bd_disk->fops->open)
 				ret = bdev->bd_disk->fops->open(bdev, mode);
@@ -1423,7 +1419,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
  out_clear:
 	disk_put_part(bdev->bd_part);
 	bdev->bd_part = NULL;
-	bdev->bd_contains = NULL;
 	return ret;
 }
 
@@ -1670,8 +1665,7 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 		disk_put_part(bdev->bd_part);
 		bdev->bd_part = NULL;
 		if (bdev_is_partition(bdev))
-			victim = bdev->bd_contains;
-		bdev->bd_contains = NULL;
+			victim = bdev_whole(bdev);
 	} else {
 		if (!bdev_is_partition(bdev) && disk->fops->release)
 			disk->fops->release(disk, mode);
@@ -1690,6 +1684,7 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
 	mutex_lock(&bdev->bd_mutex);
 
 	if (mode & FMODE_EXCL) {
+		struct block_device *whole = bdev_whole(bdev);
 		bool bdev_free;
 
 		/*
@@ -1700,13 +1695,12 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
 		spin_lock(&bdev_lock);
 
 		WARN_ON_ONCE(--bdev->bd_holders < 0);
-		WARN_ON_ONCE(--bdev->bd_contains->bd_holders < 0);
+		WARN_ON_ONCE(--whole->bd_holders < 0);
 
-		/* bd_contains might point to self, check in a separate step */
 		if ((bdev_free = !bdev->bd_holders))
 			bdev->bd_holder = NULL;
-		if (!bdev->bd_contains->bd_holders)
-			bdev->bd_contains->bd_holder = NULL;
+		if (!whole->bd_holders)
+			whole->bd_holder = NULL;
 
 		spin_unlock(&bdev_lock);
 

include/linux/blk_types.h

@@ -32,7 +32,6 @@ struct block_device {
 #ifdef CONFIG_SYSFS
 	struct list_head	bd_holder_disks;
 #endif
-	struct block_device *	bd_contains;
 	u8			bd_partno;
 	struct hd_struct *	bd_part;
 	/* number of times partitions within this device have been opened. */
@@ -49,6 +48,9 @@ struct block_device {
 	struct super_block	*bd_fsfreeze_sb;
 } __randomize_layout;
 
+#define bdev_whole(_bdev) \
+	((_bdev)->bd_disk->part0.bdev)
+
 #define bdev_kobj(_bdev) \
 	(&part_to_dev((_bdev)->bd_part)->kobj)