Re: [PATCH 01/15] btrfs: don't do find_extent_buffer in do_walk_down

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2024/4/20 03:46, Josef Bacik 写道:
> We do find_extent_buffer(), and then if we don't find the eb in cache we
> call btrfs_find_create_tree_block(), which calls find_extent_buffer()
> first and then allocates the extent buffer.
>
> The reason we're doing this is because if we don't find the extent
> buffer in cache we set reada = 1.  However this doesn't matter, because
> lower down we only trigger reada if !btrfs_buffer_uptodate(eb), which is
> what the case would be if we didn't find the extent buffer in cache and
> had to allocate it.
>
> Clean this up to simply call btrfs_find_create_tree_block(), and then
> use the fact that we're having to read the extent buffer off of disk to
> go ahead and kick off readahead.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
>   fs/btrfs/extent-tree.c | 16 ++++++----------
>   1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 023920d0d971..64bb8c69e57a 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -5434,7 +5434,6 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
>   	struct btrfs_key key;
>   	struct extent_buffer *next;
>   	int level = wc->level;
> -	int reada = 0;
>   	int ret = 0;
>   	bool need_account = false;
>
> @@ -5460,14 +5459,11 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
>   	btrfs_node_key_to_cpu(path->nodes[level], &check.first_key,
>   			      path->slots[level]);
>
> -	next = find_extent_buffer(fs_info, bytenr);
> -	if (!next) {
> -		next = btrfs_find_create_tree_block(fs_info, bytenr,
> -				btrfs_root_id(root), level - 1);
> -		if (IS_ERR(next))
> -			return PTR_ERR(next);
> -		reada = 1;
> -	}
> +	next = btrfs_find_create_tree_block(fs_info, bytenr,
> +					    btrfs_root_id(root), level - 1);
> +	if (IS_ERR(next))
> +		return PTR_ERR(next);
> +
>   	btrfs_tree_lock(next);
>
>   	ret = btrfs_lookup_extent_info(trans, fs_info, bytenr, level - 1, 1,
> @@ -5518,7 +5514,7 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
>   	}
>
>   	if (!next) {
> -		if (reada && level == 1)
> +		if (level == 1)
>   			reada_walk_down(trans, root, wc, path);
>   		next = read_tree_block(fs_info, bytenr, &check);
>   		if (IS_ERR(next)) {