Re: [PATCH] btrfs: simplify dir item location setup in btrfs_insert_xattr_item()

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

在 2026/9/26 02:22, fdmanana@kernel.org 写道:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The location (a btrfs_disk_key) of a btrfs_dir_item used for a xattr is
> always zeroed and we have a complex setup in btrfs_insert_xattr_item()
> where we declare an on stack btrfs_key, zero it out, convert it into a
> btrfs_disk_key, also declared on stack, and then pass that btrfs_disk_key
> to a btrfs_set_dir_item_key() call.
> 
> We can simplify this, and save stack space (one btrfs_disk_key and one
> btrfs_key), by simply using memzero_extent_buffer().
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

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

Thanks,
Qu

> ---
>   fs/btrfs/dir-item.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
> index 3a90736915af..d39f85035b43 100644
> --- a/fs/btrfs/dir-item.c
> +++ b/fs/btrfs/dir-item.c
> @@ -62,8 +62,7 @@ int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
>   	int ret = 0;
>   	struct btrfs_dir_item *dir_item;
>   	unsigned long name_ptr, data_ptr;
> -	struct btrfs_key key, location;
> -	struct btrfs_disk_key disk_key;
> +	struct btrfs_key key;
>   	struct extent_buffer *leaf;
>   	u32 data_size;
>   
> @@ -79,11 +78,11 @@ int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
>   					name, name_len);
>   	if (IS_ERR(dir_item))
>   		return PTR_ERR(dir_item);
> -	memset(&location, 0, sizeof(location));
>   
>   	leaf = path->nodes[0];
> -	btrfs_cpu_key_to_disk(&disk_key, &location);
> -	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
> +	memzero_extent_buffer(leaf, (unsigned long)dir_item +
> +			      offsetof(struct btrfs_dir_item, location),
> +			      sizeof(struct btrfs_disk_key));
>   	btrfs_set_dir_flags(leaf, dir_item, BTRFS_FT_XATTR);
>   	btrfs_set_dir_name_len(leaf, dir_item, name_len);
>   	btrfs_set_dir_transid(leaf, dir_item, trans->transid);