Re: [PATCH 2/3] btrfs-progs: Allow tree to be printed without an fs_info

[Su Yue <suy.fnst@cn.fujitsu.com>]

On 04/30/2018 11:15 AM, Qu Wenruo wrote:
> For btrfs_print_tree() and btrfs_print_leaf(), the usage of fs_info is
> mainly for nodesize and sectorsize.
> 
> However for nodesize, we can get it from @eb->len without the need for
> fs_info at all.
> 
> For nodesize, introduce new helper BTRFS_NODEPTR_PER_EXTENT_BUFFER() to
> get nodesize from @eb directly.
> And with the help of previous modified btrfs_leaf_free_space(),
> btrfs_print_tree() can live without fs_info at all.
> 
> For btrfs_print_leaf(), we modify print_extent_csum() to accept NULL
> fs_info by skipping csum length calculation.
> 
> With all these modification, btrfs_print_tree/leaf() can be called
> without accessing @fs_info at all, and make it more flex to handle
> binary tree block dump, or inside gdb.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>

> ---
>   ctree.h      |  7 +++++++
>   print-tree.c | 15 +++++++++++++--
>   2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/ctree.h b/ctree.h
> index e291a7d48d14..80fd19612434 100644
> --- a/ctree.h
> +++ b/ctree.h
> @@ -1202,6 +1202,13 @@ static inline u32 BTRFS_NODEPTRS_PER_BLOCK(const struct btrfs_fs_info *info)
>   	return BTRFS_LEAF_DATA_SIZE(info) / sizeof(struct btrfs_key_ptr);
>   }
>   
> +static inline u32
> +BTRFS_NODEPTRS_PER_EXTENT_BUFFER(const struct extent_buffer *eb)
> +{
> +	BUG_ON(eb->fs_info && eb->fs_info->nodesize != eb->len);
> +	return __BTRFS_LEAF_DATA_SIZE(eb->len) / sizeof(struct btrfs_key_ptr);
> +}
> +
>   #define BTRFS_FILE_EXTENT_INLINE_DATA_START		\
>   	(offsetof(struct btrfs_file_extent_item, disk_bytenr))
>   static inline u32 BTRFS_MAX_INLINE_DATA_SIZE(const struct btrfs_fs_info *info)
> diff --git a/print-tree.c b/print-tree.c
> index 34a724d5f7ef..31a851ef4413 100644
> --- a/print-tree.c
> +++ b/print-tree.c
> @@ -1150,6 +1150,14 @@ static void print_extent_csum(struct extent_buffer *eb,
>   {
>   	u32 size;
>   
> +	/*
> +	 * If we don't have fs_info, only output its start position as we
> +	 * don't have sectorsize for the calculation
> +	 */
> +	if (!fs_info) {
> +		printf("\t\trange start %llu\n", (unsigned long long)start);
> +		return;
> +	}
>   	size = (item_size / btrfs_super_csum_size(fs_info->super_copy)) *
>   			fs_info->sectorsize;
>   	printf("\t\trange start %llu end %llu length %u\n",
> @@ -1371,7 +1379,7 @@ void btrfs_print_tree(struct extent_buffer *eb, int follow)
>   	printf("node %llu level %d items %d free %u generation %llu owner ",
>   	       (unsigned long long)eb->start,
>   	        btrfs_header_level(eb), nr,
> -		(u32)BTRFS_NODEPTRS_PER_BLOCK(fs_info) - nr,
> +		(u32)BTRFS_NODEPTRS_PER_EXTENT_BUFFER(eb) - nr,
>   		(unsigned long long)btrfs_header_generation(eb));
>   	print_objectid(stdout, btrfs_header_owner(eb), 0);
>   	printf("\n");
> @@ -1385,13 +1393,16 @@ void btrfs_print_tree(struct extent_buffer *eb, int follow)
>   		btrfs_print_key(&disk_key);
>   		printf(" block %llu (%llu) gen %llu\n",
>   		       (unsigned long long)blocknr,
> -		       (unsigned long long)blocknr / fs_info->nodesize,
> +		       (unsigned long long)blocknr / eb->len,
>   		       (unsigned long long)btrfs_node_ptr_generation(eb, i));
>   		fflush(stdout);
>   	}
>   	if (!follow)
>   		return;
>   
> +	if (follow && !fs_info)
> +		return;
> +
>   	for (i = 0; i < nr; i++) {
>   		next = read_tree_block(fs_info,
>   				btrfs_node_blockptr(eb, i),
>