Re: [PATCH v2 16/17] btrfs: explicitly track file extent length and encryption

[Josef Bacik <josef@toxicpanda.com>]

On Sun, Jul 16, 2023 at 11:52:47PM -0400, Sweet Tea Dorminy wrote:
> With the advent of storing fscrypt contexts with each encrypted extent,
> extents will have a variable length depending on encryption status.
> Add accessors for the encryption field, and update all the checks for
> file extents.
> 
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
>  fs/btrfs/ctree.h                | 2 ++
>  fs/btrfs/file.c                 | 4 ++--
>  fs/btrfs/inode.c                | 9 +++++++--
>  fs/btrfs/reflink.c              | 1 +
>  fs/btrfs/tree-log.c             | 2 +-
>  include/uapi/linux/btrfs_tree.h | 5 +++++
>  6 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index f2d2b313bde5..b1afcfc62f75 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -364,6 +364,8 @@ struct btrfs_replace_extent_info {
>  	u64 file_offset;
>  	/* Pointer to a file extent item of type regular or prealloc. */
>  	char *extent_buf;
> +	/* The length of @extent_buf */
> +	u32 extent_buf_size;
>  	/*
>  	 * Set to true when attempting to replace a file range with a new extent
>  	 * described by this structure, set to false when attempting to clone an
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 73038908876a..4988c9317234 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -2246,14 +2246,14 @@ static int btrfs_insert_replace_extent(struct btrfs_trans_handle *trans,
>  	key.type = BTRFS_EXTENT_DATA_KEY;
>  	key.offset = extent_info->file_offset;
>  	ret = btrfs_insert_empty_item(trans, root, path, &key,
> -				      sizeof(struct btrfs_file_extent_item));
> +				      extent_info->extent_buf_size);
>  	if (ret)
>  		return ret;
>  	leaf = path->nodes[0];
>  	slot = path->slots[0];
>  	write_extent_buffer(leaf, extent_info->extent_buf,
>  			    btrfs_item_ptr_offset(leaf, slot),
> -			    sizeof(struct btrfs_file_extent_item));
> +			    extent_info->extent_buf_size);
>  	extent = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
>  	ASSERT(btrfs_file_extent_type(leaf, extent) != BTRFS_FILE_EXTENT_INLINE);
>  	btrfs_set_file_extent_offset(leaf, extent, extent_info->data_offset);
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index f68d74dec5ed..83098779dad2 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3036,6 +3036,9 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
>  	u64 num_bytes = btrfs_stack_file_extent_num_bytes(stack_fi);
>  	u64 ram_bytes = btrfs_stack_file_extent_ram_bytes(stack_fi);
>  	struct btrfs_drop_extents_args drop_args = { 0 };
> +	size_t fscrypt_context_size =
> +		btrfs_stack_file_extent_encryption(stack_fi) ?
> +			FSCRYPT_SET_CONTEXT_MAX_SIZE : 0;
>  	int ret;
>  
>  	path = btrfs_alloc_path();
> @@ -3055,7 +3058,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
>  	drop_args.start = file_pos;
>  	drop_args.end = file_pos + num_bytes;
>  	drop_args.replace_extent = true;
> -	drop_args.extent_item_size = sizeof(*stack_fi);
> +	drop_args.extent_item_size = sizeof(*stack_fi) + fscrypt_context_size;
>  	ret = btrfs_drop_extents(trans, root, inode, &drop_args);
>  	if (ret)
>  		goto out;
> @@ -3066,7 +3069,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
>  		ins.type = BTRFS_EXTENT_DATA_KEY;
>  
>  		ret = btrfs_insert_empty_item(trans, root, path, &ins,
> -					      sizeof(*stack_fi));
> +					      sizeof(*stack_fi) + fscrypt_context_size);
>  		if (ret)
>  			goto out;
>  	}
> @@ -9770,6 +9773,7 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
>  	u64 len = ins->offset;
>  	int qgroup_released;
>  	int ret;
> +	size_t fscrypt_context_size = 0;
>  
>  	memset(&stack_fi, 0, sizeof(stack_fi));
>  
> @@ -9802,6 +9806,7 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
>  	extent_info.data_len = len;
>  	extent_info.file_offset = file_offset;
>  	extent_info.extent_buf = (char *)&stack_fi;
> +	extent_info.extent_buf_size = sizeof(stack_fi) + fscrypt_context_size;
>  	extent_info.is_new_extent = true;
>  	extent_info.update_times = true;
>  	extent_info.qgroup_reserved = qgroup_released;
> diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
> index ad722f495c9b..9f3b5748f39b 100644
> --- a/fs/btrfs/reflink.c
> +++ b/fs/btrfs/reflink.c
> @@ -502,6 +502,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
>  			clone_info.data_len = datal;
>  			clone_info.file_offset = new_key.offset;
>  			clone_info.extent_buf = buf;
> +			clone_info.extent_buf_size = size;
>  			clone_info.is_new_extent = false;
>  			clone_info.update_times = !no_time_update;
>  			ret = btrfs_replace_file_extents(BTRFS_I(inode), path,
> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> index a49a05cfbac4..82c91097672b 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -4689,7 +4689,7 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
>  		key.offset = em->start;
>  
>  		ret = btrfs_insert_empty_item(trans, log, path, &key,
> -					      sizeof(fi));
> +					      sizeof(fi) + fscrypt_context_size);
>  		if (ret)
>  			return ret;
>  	}
> diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
> index 029af0aeb65d..ea4903cfd926 100644
> --- a/include/uapi/linux/btrfs_tree.h
> +++ b/include/uapi/linux/btrfs_tree.h
> @@ -1048,6 +1048,11 @@ struct btrfs_file_extent_item {
>  	 * but not for stat.
>  	 */
>  	__u8 compression;
> +
> +	/*
> +	 * 2 bits of encryption type in the lower bits, 6 bits of context size
> +	 * in the upper bits. Unencrypted value is 0.
> +	 */

Additionally this comment needed to be in the patch changing the format.
Thanks,

Josef