[PATCH block/for-next v2 01/16] block: add a new helper to get inode from block_device

[Yu Kuai <yukuai1@huaweicloud.com>]

From: Yu Kuai <yukuai3@huawei.com>

block_devcie is allocated from bdev_alloc() by bdev_alloc_inode(), and
currently block_device contains a pointer that point to the address of
inode, while such inode is allocated together:

bdev_alloc
 inode = new_inode()
  // inode is &bdev_inode->vfs_inode
 bdev = I_BDEV(inode)
  // bdev is &bdev_inode->bdev
 bdev->inode = inode

Add a new helper to get address of inode from bdev by add operation
instead of memory access, which is more efficiency.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/bdev.c              |  5 -----
 include/linux/blk_types.h | 12 ++++++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index e4cfb7adb645..7509389095b7 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -30,11 +30,6 @@
 #include "../fs/internal.h"
 #include "blk.h"
 
-struct bdev_inode {
-	struct block_device bdev;
-	struct inode vfs_inode;
-};
-
 static inline struct bdev_inode *BDEV_I(struct inode *inode)
 {
 	return container_of(inode, struct bdev_inode, vfs_inode);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d5c5e59ddbd2..06de8393dcd1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -85,6 +85,18 @@ struct block_device {
 #define bdev_kobj(_bdev) \
 	(&((_bdev)->bd_device.kobj))
 
+struct bdev_inode {
+	struct block_device bdev;
+	struct inode vfs_inode;
+};
+
+static inline struct inode *bdev_inode(struct block_device *bdev)
+{
+	struct bdev_inode *bi = container_of(bdev, struct bdev_inode, bdev);
+
+	return &bi->vfs_inode;
+}
+
 /*
  * Block error status values.  See block/blk-core:blk_errors for the details.
  * Alpha cannot write a byte atomically, so we need to use 32-bit value.
-- 
2.39.2