Btrfs: kill free_space pointer from inode structure

Inodes always allocate free space with BTRFS_BLOCK_GROUP_DATA type,
which means every inode has the same BTRFS_I(inode)->free_space pointer.

This shrinks struct btrfs_inode by 4 bytes (or 8 bytes on 64 bits).
Signed-off-by: Li Zefan <lizefan@huawei.com>

fs/btrfs/btrfs_inode.h

@@ -87,9 +87,6 @@ struct btrfs_inode {
 	/* node for the red-black tree that links inodes in subvolume root */
 	struct rb_node rb_node;
 
-	/* the space_info for where this inode's data allocations are done */
-	struct btrfs_space_info *space_info;
-
 	unsigned long runtime_flags;
 
 	/* full 64 bit generation number, struct vfs_inode doesn't have a big

fs/btrfs/ctree.h

@@ -1240,6 +1240,8 @@ struct btrfs_fs_info {
 	 */
 	struct list_head space_info;
 
+	struct btrfs_space_info *data_sinfo;
+
 	struct reloc_control *reloc_ctl;
 
 	spinlock_t delalloc_lock;
@@ -2607,7 +2609,6 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root, u64 group_start);
 u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags);
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
-void btrfs_set_inode_space_info(struct btrfs_root *root, struct inode *ionde);
 void btrfs_clear_space_info_full(struct btrfs_fs_info *info);
 int btrfs_check_data_free_space(struct inode *inode, u64 bytes);
 void btrfs_free_reserved_data_space(struct inode *inode, u64 bytes);

fs/btrfs/extent-tree.c

@@ -3139,6 +3139,8 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
 	init_waitqueue_head(&found->wait);
 	*space_info = found;
 	list_add_rcu(&found->list, &info->space_info);
+	if (flags & BTRFS_BLOCK_GROUP_DATA)
+		info->data_sinfo = found;
 	return 0;
 }
 
@@ -3268,12 +3270,6 @@ u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data)
 	return get_alloc_profile(root, flags);
 }
 
-void btrfs_set_inode_space_info(struct btrfs_root *root, struct inode *inode)
-{
-	BTRFS_I(inode)->space_info = __find_space_info(root->fs_info,
-						       BTRFS_BLOCK_GROUP_DATA);
-}
-
 /*
  * This will check the space that the inode allocates from to make sure we have
  * enough space for bytes.
@@ -3282,6 +3278,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes)
 {
 	struct btrfs_space_info *data_sinfo;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_fs_info *fs_info = root->fs_info;
 	u64 used;
 	int ret = 0, committed = 0, alloc_chunk = 1;
 
@@ -3294,7 +3291,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes)
 		committed = 1;
 	}
 
-	data_sinfo = BTRFS_I(inode)->space_info;
+	data_sinfo = fs_info->data_sinfo;
 	if (!data_sinfo)
 		goto alloc;
 
@@ -3335,10 +3332,9 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes)
 					goto commit_trans;
 			}
 
-			if (!data_sinfo) {
-				btrfs_set_inode_space_info(root, inode);
-				data_sinfo = BTRFS_I(inode)->space_info;
-			}
+			if (!data_sinfo)
+				data_sinfo = fs_info->data_sinfo;
+
 			goto again;
 		}
 
@@ -3385,7 +3381,7 @@ void btrfs_free_reserved_data_space(struct inode *inode, u64 bytes)
 	/* make sure bytes are sectorsize aligned */
 	bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
 
-	data_sinfo = BTRFS_I(inode)->space_info;
+	data_sinfo = root->fs_info->data_sinfo;
 	spin_lock(&data_sinfo->lock);
 	data_sinfo->bytes_may_use -= bytes;
 	trace_btrfs_space_reservation(root->fs_info, "space_info",

fs/btrfs/inode.c

@@ -4082,7 +4082,6 @@ static int btrfs_init_locked_inode(struct inode *inode, void *p)
 	struct btrfs_iget_args *args = p;
 	inode->i_ino = args->ino;
 	BTRFS_I(inode)->root = args->root;
-	btrfs_set_inode_space_info(args->root, inode);
 	return 0;
 }
 
@@ -4667,7 +4666,6 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	BTRFS_I(inode)->root = root;
 	BTRFS_I(inode)->generation = trans->transid;
 	inode->i_generation = BTRFS_I(inode)->generation;
-	btrfs_set_inode_space_info(root, inode);
 
 	if (S_ISDIR(mode))
 		owner = 0;
@@ -6944,7 +6942,6 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
 		return NULL;
 
 	ei->root = NULL;
-	ei->space_info = NULL;
 	ei->generation = 0;
 	ei->last_trans = 0;
 	ei->last_sub_trans = 0;