On 5.09.2018 09:29, Qu Wenruo wrote:
> btrfs_print_tree() uses depth-first search to print a subtree, it works
> fine until we have 3 level tree.
>
> In that case, leaves and nodes will be printed in a depth-first order,
> making it pretty hard to locate level 1 nodes.
>
> This patch will use breadth-first search for btrfs_print_tree().
> It will use btrfs_path::lowest_level to indicate current level, and
> print out tree blocks level by level (breadth-first).
>
> Signed-off-by: Qu Wenruo <w...@suse.com>
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
> ---
> print-tree.c | 99 ++++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 73 insertions(+), 26 deletions(-)
>
> diff --git a/print-tree.c b/print-tree.c
> index 31f6fa12522f..0509ec3da46e 100644
> --- a/print-tree.c
> +++ b/print-tree.c
> @@ -1381,6 +1381,78 @@ void btrfs_print_leaf(struct extent_buffer *eb)
> }
> }
>
> +/* Helper function to reach the most left tree block at @path->lowest_level
> */
> +static int search_leftmost_tree_block(struct btrfs_fs_info *fs_info,
> + struct btrfs_path *path, int root_level)
> +{
> + int i;
> + int ret = 0;
> +
> + /* Release all nodes expect path->nodes[root_level] */
> + for (i = 0; i < root_level; i++) {
> + path->slots[i] = 0;
> + if (!path->nodes[i])
> + continue;
> + free_extent_buffer(path->nodes[i]);
> + }
> +
> + /* Reach the leftmost tree block by always reading out slot 0 */
> + for (i = root_level; i > path->lowest_level; i--) {
> + struct extent_buffer *eb;
> +
> + path->slots[i] = 0;
> + eb = read_node_slot(fs_info, path->nodes[i], 0);
> + if (!extent_buffer_uptodate(eb)) {
> + ret = -EIO;
> + goto out;
> + }
> + path->nodes[i - 1] = eb;
> + }
> +out:
> + return ret;
> +}
> +
> +static void bfs_print_children(struct extent_buffer *root_eb)
> +{
> + struct btrfs_fs_info *fs_info = root_eb->fs_info;
> + struct btrfs_path path;
> + int root_level = btrfs_header_level(root_eb);
> + int cur_level;
> + int ret;
> +
> + if (root_level < 1)
> + return;
> +
> + btrfs_init_path(&path);
> + /* For path */
> + extent_buffer_get(root_eb);
> + path.nodes[root_level] = root_eb;
> +
> + for (cur_level = root_level - 1; cur_level >= 0; cur_level--) {
> + path.lowest_level = cur_level;
> +
> + /* Use the leftmost tree block as start point */
> + ret = search_leftmost_tree_block(fs_info, &path, root_level);
So what you do here is really get the leftmost item at until level
'cur_level'.
> + if (ret < 0)
> + goto out;
> +
> + /* Print all sibling tree blocks */
> + while (1) {
> + btrfs_print_tree(path.nodes[cur_level], 0);
Then you print the block.
> + ret = btrfs_next_sibling_tree_block(fs_info, &path);
And this just loads the next block at level 'cur_level', representing
the "breadth" portion.
> + if (ret < 0)
> + goto out;
> + if (ret > 0) {
> + ret = 0;
> + break;
> + }
> + }
> + }
> +out:
> + btrfs_release_path(&path);
> + return;
> +}
> +
> void btrfs_print_tree(struct extent_buffer *eb, int follow)
> {
> u32 i;
> @@ -1389,7 +1461,6 @@ void btrfs_print_tree(struct extent_buffer *eb, int
> follow)
> struct btrfs_fs_info *fs_info = eb->fs_info;
> struct btrfs_disk_key disk_key;
> struct btrfs_key key;
> - struct extent_buffer *next;
>
> if (!eb)
> return;
> @@ -1431,30 +1502,6 @@ void btrfs_print_tree(struct extent_buffer *eb, int
> follow)
> if (follow && !fs_info)
> return;
>
> - for (i = 0; i < nr; i++) {
> - next = read_tree_block(fs_info,
> - btrfs_node_blockptr(eb, i),
> - btrfs_node_ptr_generation(eb, i));
> - if (!extent_buffer_uptodate(next)) {
> - fprintf(stderr, "failed to read %llu in tree %llu\n",
> - (unsigned long long)btrfs_node_blockptr(eb, i),
> - (unsigned long long)btrfs_header_owner(eb));
> - continue;
> - }
> - if (btrfs_header_level(next) != btrfs_header_level(eb) - 1) {
> - warning(
> -"eb corrupted: parent bytenr %llu slot %d level %d child bytenr %llu level
> has %d expect %d, skipping the slot",
> - btrfs_header_bytenr(eb), i,
> - btrfs_header_level(eb),
> - btrfs_header_bytenr(next),
> - btrfs_header_level(next),
> - btrfs_header_level(eb) - 1);
> - free_extent_buffer(next);
> - continue;
> - }
> - btrfs_print_tree(next, 1);
> - free_extent_buffer(next);
> - }
> -
> + bfs_print_children(eb);
> return;
> }
>
