Re: [PATCH v2 2/3] btrfs: replace stripe extents

[Naohiro Aota]

On Thu, Jul 11, 2024 at 08:21:31AM GMT, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> 
> Update stripe extents in case a write to an already existing address
> incoming.
> 
> Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> ---
>  fs/btrfs/raid-stripe-tree.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
> index e6f7a234b8f6..fd56535b2289 100644
> --- a/fs/btrfs/raid-stripe-tree.c
> +++ b/fs/btrfs/raid-stripe-tree.c
> @@ -73,6 +73,55 @@ int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start, u64 le
>  	return ret;
>  }
>  
> +static int update_raid_extent_item(struct btrfs_trans_handle *trans,
> +				   struct btrfs_key *key,
> +				   struct btrfs_io_context *bioc)
> +{
> +	struct btrfs_path *path;
> +	struct extent_buffer *leaf;
> +	struct btrfs_stripe_extent *stripe_extent;
> +	int num_stripes;
> +	int ret;
> +	int slot;
> +
> +	path = btrfs_alloc_path();
> +	if (!path)
> +		return -ENOMEM;
> +
> +	ret = btrfs_search_slot(trans, trans->fs_info->stripe_root, key, path,
> +				0, 1);
> +	if (ret)
> +		return ret == 1 ? ret : -EINVAL;
> +
> +	leaf = path->nodes[0];
> +	slot = path->slots[0];
> +
> +	btrfs_item_key_to_cpu(leaf, key, slot);
> +	num_stripes = btrfs_num_raid_stripes(btrfs_item_size(leaf, slot));
> +	stripe_extent = btrfs_item_ptr(leaf, slot, struct btrfs_stripe_extent);
> +
> +	ASSERT(key->offset == bioc->size);
> +
> +	for (int i = 0; i < num_stripes; i++) {
> +		u64 devid = bioc->stripes[i].dev->devid;
> +		u64 physical = bioc->stripes[i].physical;
> +		u64 length = bioc->stripes[i].length;
> +		struct btrfs_raid_stride *raid_stride =
> +			&stripe_extent->strides[i];
> +
> +		if (length == 0)
> +			length = bioc->size;
> +
> +		btrfs_set_raid_stride_devid(leaf, raid_stride, devid);
> +		btrfs_set_raid_stride_physical(leaf, raid_stride, physical);
> +	}

Can we take the "stripe_extent" and item_size and use write_extent_buffer()
to overwrite the item here? Then, we don't need duplicated code.

> +
> +	btrfs_mark_buffer_dirty(trans, leaf);
> +	btrfs_free_path(path);
> +
> +	return ret;
> +}
> +
>  static int btrfs_insert_one_raid_extent(struct btrfs_trans_handle *trans,
>  					struct btrfs_io_context *bioc)
>  {
> @@ -112,6 +161,8 @@ static int btrfs_insert_one_raid_extent(struct btrfs_trans_handle *trans,
>  
>  	ret = btrfs_insert_item(trans, stripe_root, &stripe_key, stripe_extent,
>  				item_size);
> +	if (ret == -EEXIST)
> +		ret = update_raid_extent_item(trans, &stripe_key, bioc);
>  	if (ret)
>  		btrfs_abort_transaction(trans, ret);
>  
> 
> -- 
> 2.43.0
>