btrfs: drop transaction parameter from btrfs_add_inode_defrag()

There's only one caller inode_should_defrag() that passes NULL to
btrfs_add_inode_defrag() so we can drop it an simplify the code.

Reviewed-by: Qu Wenruo <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/defrag.c

···
  * Insert a defrag record for this inode if auto defrag is enabled. No errors
  * returned as they're not considered fatal.
  */
-void btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
-			    struct btrfs_inode *inode, u32 extent_thresh)
+void btrfs_add_inode_defrag(struct btrfs_inode *inode, u32 extent_thresh)
 {
 	struct btrfs_root *root = inode->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct inode_defrag *defrag;
-	u64 transid;
 	int ret;
 
 	if (!need_auto_defrag(fs_info))
···
 	if (test_bit(BTRFS_INODE_IN_DEFRAG, &inode->runtime_flags))
 		return;
 
-	if (trans)
-		transid = trans->transid;
-	else
-		transid = btrfs_get_root_last_trans(root);
-
 	defrag = kmem_cache_zalloc(btrfs_inode_defrag_cachep, GFP_NOFS);
 	if (!defrag)
 		return;
 
 	defrag->ino = btrfs_ino(inode);
-	defrag->transid = transid;
+	defrag->transid = btrfs_get_root_last_trans(root);
 	defrag->root = btrfs_root_id(root);
 	defrag->extent_thresh = extent_thresh;
 

fs/btrfs/defrag.h

···
 		      u64 newer_than, unsigned long max_to_defrag);
 int __init btrfs_auto_defrag_init(void);
 void __cold btrfs_auto_defrag_exit(void);
-void btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
-			    struct btrfs_inode *inode, u32 extent_thresh);
+void btrfs_add_inode_defrag(struct btrfs_inode *inode, u32 extent_thresh);
 int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info);
 void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info);
 int btrfs_defrag_root(struct btrfs_root *root);

fs/btrfs/inode.c

···
 	/* If this is a small write inside eof, kick off a defrag */
 	if (num_bytes < small_write &&
 	    (start > 0 || end + 1 < inode->disk_i_size))
-		btrfs_add_inode_defrag(NULL, inode, small_write);
+		btrfs_add_inode_defrag(inode, small_write);
 }
 
 static int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)