Re: [PATCH 1/5] btrfs: factor init_extent_buffer from __alloc_extent_buffer

On 6/24/26 12:35 AM, Boris Burkov wrote:
> In preparation for preallocating extent_buffer data, factor eb
> initialization away from specifically allocating it. This allows us to
> allocate the eb, bfs, folios, etc. together in the main search_slot code
> paths, but still share initialization code with the dummy/test/clone
> allocation paths.
>
> Signed-off-by: Boris Burkov <[email protected]>
> ---
>   fs/btrfs/extent_io.c | 20 ++++++++++++--------
>   1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 0edd532174fa..fa4cc8bcd1af 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3054,12 +3054,9 @@ void btrfs_uninhibit_all_eb_writeback(struct btrfs_trans_handle *trans)
>   	xa_destroy(&trans->writeback_inhibited_ebs);
>   }
>   
> -static struct extent_buffer *__alloc_extent_buffer(struct btrfs_fs_info *fs_info,
> -						   u64 start)
> +static void init_extent_buffer(struct btrfs_fs_info *fs_info,
> +			       struct extent_buffer *eb, u64 start)
>   {
> -	struct extent_buffer *eb = NULL;
> -
> -	eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
>   	eb->start = start;
>   	eb->len = fs_info->nodesize;
>   	eb->fs_info = fs_info;
> @@ -3072,7 +3069,15 @@ static struct extent_buffer *__alloc_extent_buffer(struct btrfs_fs_info *fs_info
>   	refcount_set(&eb->refs, 1);
>   
>   	ASSERT(eb->len <= BTRFS_MAX_METADATA_BLOCKSIZE);
> +}
> +
> +static struct extent_buffer *__alloc_extent_buffer(struct btrfs_fs_info *fs_info,
> +						   u64 start)
> +{
> +	struct extent_buffer *eb;
>   
> +	eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS | __GFP_NOFAIL);
> +	init_extent_buffer(fs_info, eb, start);
>   	return eb;
>   }
>   
> @@ -3476,9 +3481,8 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
>   	if (eb)
>   		return eb;
>   
> -	eb = __alloc_extent_buffer(fs_info, start);
> -	if (!eb)
> -		return ERR_PTR(-ENOMEM);
> +	eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS | __GFP_NOFAIL);
> +	init_extent_buffer(fs_info, eb, start);
>   
>   	/*
>   	 * The reloc trees are just snapshots, so we need them to appear to be

This looks wrong to me. Not the split out code, but how it is used in 
alloc_extent_buffer(). Either you keep calling __alloc_extent_buffer() 
in alloc_extent_buffer() OR don't call init_extent_buffer() in 
__alloc_extent_buffer(). I see this is an intermediate step (and I 
haven't looked at the rest of the series yet) but it looks wrong.