btrfs: introduce btrfs_is_data_reloc_root

There are several places in our codebase where we check if a root is the
root of the data reloc tree and subsequent patches will introduce more.

Factor out the check into a small helper function instead of open coding
it multiple times.

Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3846,6 +3846,11 @@ static inline bool btrfs_is_zoned(const struct btrfs_fs_info *fs_info)
 	return fs_info->zoned != 0;
 }
 
+static inline bool btrfs_is_data_reloc_root(const struct btrfs_root *root)
+{
+	return root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID;
+}
+
 /*
  * We use page status Private2 to indicate there is an ordered extent with
  * unfinished IO.

fs/btrfs/disk-io.c

@@ -1500,7 +1500,7 @@ static int btrfs_init_fs_root(struct btrfs_root *root, dev_t anon_dev)
 		goto fail;
 
 	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID &&
-	    root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID) {
+	    !btrfs_is_data_reloc_root(root)) {
 		set_bit(BTRFS_ROOT_SHAREABLE, &root->state);
 		btrfs_check_and_init_root_item(&root->root_item);
 	}

fs/btrfs/extent-tree.c

@@ -2376,7 +2376,7 @@ int btrfs_cross_ref_exist(struct btrfs_root *root, u64 objectid, u64 offset,
 
 out:
 	btrfs_free_path(path);
-	if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
+	if (btrfs_is_data_reloc_root(root))
 		WARN_ON(ret > 0);
 	return ret;
 }

fs/btrfs/inode.c

@@ -1150,7 +1150,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 	 * fails during the stage where it updates the bytenr of file extent
 	 * items.
 	 */
-	if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
+	if (btrfs_is_data_reloc_root(root))
 		min_alloc_size = num_bytes;
 	else
 		min_alloc_size = fs_info->sectorsize;
@@ -1186,8 +1186,7 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 		if (ret)
 			goto out_drop_extent_cache;
 
-		if (root->root_key.objectid ==
-		    BTRFS_DATA_RELOC_TREE_OBJECTID) {
+		if (btrfs_is_data_reloc_root(root)) {
 			ret = btrfs_reloc_clone_csums(inode, start,
 						      cur_alloc_size);
 			/*
@@ -1503,8 +1502,7 @@ static int fallback_to_cow(struct btrfs_inode *inode, struct page *locked_page,
 			   int *page_started, unsigned long *nr_written)
 {
 	const bool is_space_ino = btrfs_is_free_space_inode(inode);
-	const bool is_reloc_ino = (inode->root->root_key.objectid ==
-				   BTRFS_DATA_RELOC_TREE_OBJECTID);
+	const bool is_reloc_ino = btrfs_is_data_reloc_root(inode->root);
 	const u64 range_bytes = end + 1 - start;
 	struct extent_io_tree *io_tree = &inode->io_tree;
 	u64 range_start = start;
@@ -1866,8 +1864,7 @@ out_check:
 			btrfs_dec_nocow_writers(fs_info, disk_bytenr);
 		nocow = false;
 
-		if (root->root_key.objectid ==
-		    BTRFS_DATA_RELOC_TREE_OBJECTID)
+		if (btrfs_is_data_reloc_root(root))
 			/*
 			 * Error handled later, as we must prevent
 			 * extent_clear_unlock_delalloc() in error handler
@@ -2206,7 +2203,7 @@ void btrfs_clear_delalloc_extent(struct inode *vfs_inode,
 		if (btrfs_is_testing(fs_info))
 			return;
 
-		if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID &&
+		if (!btrfs_is_data_reloc_root(root) &&
 		    do_list && !(state->state & EXTENT_NORESERVE) &&
 		    (*bits & EXTENT_CLEAR_DATA_RESV))
 			btrfs_free_reserved_data_space_noquota(fs_info, len);
@@ -2531,7 +2528,7 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 		goto mapit;
 	} else if (async && !skip_sum) {
 		/* csum items have already been cloned */
-		if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
+		if (btrfs_is_data_reloc_root(root))
 			goto mapit;
 		/* we're doing a write, do the async checksumming */
 		ret = btrfs_wq_submit_bio(inode, bio, mirror_num, bio_flags,
@@ -3307,7 +3304,7 @@ unsigned int btrfs_verify_data_csum(struct btrfs_io_bio *io_bio, u32 bio_offset,
 		u64 file_offset = pg_off + page_offset(page);
 		int ret;
 
-		if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID &&
+		if (btrfs_is_data_reloc_root(root) &&
 		    test_range_bit(io_tree, file_offset,
 				   file_offset + sectorsize - 1,
 				   EXTENT_NODATASUM, 1, NULL)) {
@@ -4008,7 +4005,7 @@ noinline int btrfs_update_inode(struct btrfs_trans_handle *trans,
 	 * without delay
 	 */
 	if (!btrfs_is_free_space_inode(inode)
-	    && root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
+	    && !btrfs_is_data_reloc_root(root)
 	    && !test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags)) {
 		btrfs_update_root_times(trans, root);
 

fs/btrfs/relocation.c

@@ -4390,8 +4390,7 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
 	if (!rc)
 		return 0;
 
-	BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
-	       root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
+	BUG_ON(rc->stage == UPDATE_DATA_PTRS && btrfs_is_data_reloc_root(root));
 
 	level = btrfs_header_level(buf);
 	if (btrfs_header_generation(buf) <=