[dm-devel] [PATCH stable 5.10 1/3] block: look up holders by bdev

[Yu Kuai]

From: Christoph Hellwig <hch at lst.de>

commit 0dbcfe247f22a6d73302dfa691c48b3c14d31c4c upstream.

Invert they way the holder relations are tracked.  This very
slightly reduces the memory overhead for partitioned devices.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Yu Kuai <yukuai3 at huawei.com>
---
 block/genhd.c             |  3 +++
 fs/block_dev.c            | 31 +++++++++++++++++++------------
 include/linux/blk_types.h |  3 ---
 include/linux/genhd.h     |  4 +++-
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 796baf761202..2b11a2735285 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1760,6 +1760,9 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
 	disk_to_dev(disk)->class = &block_class;
 	disk_to_dev(disk)->type = &disk_type;
 	device_initialize(disk_to_dev(disk));
+#ifdef CONFIG_SYSFS
+	INIT_LIST_HEAD(&disk->slave_bdevs);
+#endif
 	return disk;
 
 out_free_part0:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 29f020c4b2d0..a202c76fcf7f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -823,9 +823,6 @@ static void init_once(void *foo)
 
 	memset(bdev, 0, sizeof(*bdev));
 	mutex_init(&bdev->bd_mutex);
-#ifdef CONFIG_SYSFS
-	INIT_LIST_HEAD(&bdev->bd_holder_disks);
-#endif
 	bdev->bd_bdi = &noop_backing_dev_info;
 	inode_init_once(&ei->vfs_inode);
 	/* Initialize mutex for freeze. */
@@ -1188,7 +1185,7 @@ EXPORT_SYMBOL(bd_abort_claiming);
 #ifdef CONFIG_SYSFS
 struct bd_holder_disk {
 	struct list_head	list;
-	struct gendisk		*disk;
+	struct block_device	*bdev;
 	int			refcnt;
 };
 
@@ -1197,8 +1194,8 @@ static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
 {
 	struct bd_holder_disk *holder;
 
-	list_for_each_entry(holder, &bdev->bd_holder_disks, list)
-		if (holder->disk == disk)
+	list_for_each_entry(holder, &disk->slave_bdevs, list)
+		if (holder->bdev == bdev)
 			return holder;
 	return NULL;
 }
@@ -1244,9 +1241,13 @@ static void del_symlink(struct kobject *from, struct kobject *to)
 int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 {
 	struct bd_holder_disk *holder;
+	struct block_device *bdev_holder = bdget_disk(disk, 0);
 	int ret = 0;
 
-	mutex_lock(&bdev->bd_mutex);
+	if (WARN_ON_ONCE(!bdev_holder))
+		return -ENOENT;
+
+	mutex_lock(&bdev_holder->bd_mutex);
 
 	WARN_ON_ONCE(!bdev->bd_holder);
 
@@ -1267,7 +1268,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	}
 
 	INIT_LIST_HEAD(&holder->list);
-	holder->disk = disk;
+	holder->bdev = bdev;
 	holder->refcnt = 1;
 
 	ret = add_symlink(disk->slave_dir, &part_to_dev(bdev->bd_part)->kobj);
@@ -1283,7 +1284,7 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	 */
 	kobject_get(bdev->bd_part->holder_dir);
 
-	list_add(&holder->list, &bdev->bd_holder_disks);
+	list_add(&holder->list, &disk->slave_bdevs);
 	goto out_unlock;
 
 out_del:
@@ -1291,7 +1292,8 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 out_free:
 	kfree(holder);
 out_unlock:
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&bdev_holder->bd_mutex);
+	bdput(bdev_holder);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
@@ -1309,8 +1311,12 @@ EXPORT_SYMBOL_GPL(bd_link_disk_holder);
 void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 {
 	struct bd_holder_disk *holder;
+	struct block_device *bdev_holder = bdget_disk(disk, 0);
 
-	mutex_lock(&bdev->bd_mutex);
+	if (WARN_ON_ONCE(!bdev_holder))
+		return;
+
+	mutex_lock(&bdev_holder->bd_mutex);
 
 	holder = bd_find_holder_disk(bdev, disk);
 
@@ -1323,7 +1329,8 @@ void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
 		kfree(holder);
 	}
 
-	mutex_unlock(&bdev->bd_mutex);
+	mutex_unlock(&bdev_holder->bd_mutex);
+	bdput(bdev_holder);
 }
 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
 #endif
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d9b69bbde5cc..1b84ecb34c18 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -29,9 +29,6 @@ struct block_device {
 	void *			bd_holder;
 	int			bd_holders;
 	bool			bd_write_holder;
-#ifdef CONFIG_SYSFS
-	struct list_head	bd_holder_disks;
-#endif
 	struct block_device *	bd_contains;
 	u8			bd_partno;
 	struct hd_struct *	bd_part;
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 03da3f603d30..3e5049a527e6 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -195,7 +195,9 @@ struct gendisk {
 #define GD_NEED_PART_SCAN		0
 	struct rw_semaphore lookup_sem;
 	struct kobject *slave_dir;
-
+#ifdef CONFIG_SYSFS
+	struct list_head	slave_bdevs;
+#endif
 	struct timer_rand_state *random;
 	atomic_t sync_io;		/* RAID */
 	struct disk_events *ev;
-- 
2.31.1