Re: [PATCH v11 06/10] btrfs-progs: receive: encoded_write fallback to explicit decode and write

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On 1.09.21 г. 20:01, Omar Sandoval wrote:
> From: Boris Burkov <boris@xxxxxx>
> 

<snip>

> @@ -79,6 +83,12 @@ struct btrfs_receive
>  	struct subvol_uuid_search sus;
>  
>  	int honor_end_cmd;
> +
> +	int force_decompress;

Make it bool

> +
> +	/* Reuse stream objects for encoded_write decompression fallback */
> +	ZSTD_DStream *zstd_dstream;
> +	z_stream *zlib_stream;
>  };
>  
>  static int finish_subvol(struct btrfs_receive *rctx)
> @@ -989,9 +999,222 @@ static int process_update_extent(const char *path, u64 offset, u64 len,
>  	return 0;
>  }
>  

<snip>

> +
> +static int decompress_lzo(const char *encoded_data, u64 encoded_len,
> +			  char *unencoded_data, u64 unencoded_len,
> +			  unsigned int page_size)
> +{
> +	uint32_t total_len;
> +	size_t in_pos, out_pos;
> +
> +	if (encoded_len < 4) {
> +		error("lzo header is truncated");
> +		return -EIO;
> +	}
> +	memcpy(&total_len, encoded_data, 4);
> +	total_len = le32toh(total_len);
> +	if (total_len > encoded_len) {
> +		error("lzo header is invalid");
> +		return -EIO;
> +	}
> +
> +	in_pos = 4;
> +	out_pos = 0;
> +	while (in_pos < total_len && out_pos < unencoded_len) {
> +		size_t page_remaining;
> +		uint32_t src_len;
> +		lzo_uint dst_len;
> +		int ret;
> +
> +		page_remaining = -in_pos % page_size;

Why the -in_pos?

> +		if (page_remaining < 4) {
> +			if (total_len - in_pos <= page_remaining)
> +				break;
> +			in_pos += page_remaining;
> +		}
> +
> +		if (total_len - in_pos < 4) {
> +			error("lzo segment header is truncated");
> +			return -EIO;
> +		}
> +
> +		memcpy(&src_len, encoded_data + in_pos, 4);
> +		src_len = le32toh(src_len);
> +		in_pos += 4;
> +		if (src_len > total_len - in_pos) {
> +			error("lzo segment header is invalid");
> +			return -EIO;
> +		}
> +
> +		dst_len = page_size;
> +		ret = lzo1x_decompress_safe((void *)(encoded_data + in_pos),
> +					    src_len,
> +					    (void *)(unencoded_data + out_pos),
> +					    &dst_len, NULL);
> +		if (ret != LZO_E_OK) {
> +			error("lzo1x_decompress_safe failed: %d", ret);
> +			return -EIO;
> +		}
> +
> +		in_pos += src_len;
> +		out_pos += dst_len;
> +	}
> +	return 0;
> +}
> +
> +static int decompress_and_write(struct btrfs_receive *rctx,
> +				const char *encoded_data, u64 offset,
> +				u64 encoded_len, u64 unencoded_file_len,
> +				u64 unencoded_len, u64 unencoded_offset,
> +				u32 compression)
> +{
> +	int ret = 0;
> +	size_t pos;
> +	ssize_t w;
> +	char *unencoded_data;
> +	int page_shift;
> +
> +	unencoded_data = calloc(unencoded_len, 1);
> +	if (!unencoded_data) {
> +		error("allocating space for unencoded data failed: %m");
> +		return -errno;
> +	}
> +
> +	switch (compression) {
> +	case BTRFS_ENCODED_IO_COMPRESSION_ZLIB:
> +		ret = decompress_zlib(rctx, encoded_data, encoded_len,
> +				      unencoded_data, unencoded_len);
> +		if (ret)
> +			goto out;
> +		break;
> +	case BTRFS_ENCODED_IO_COMPRESSION_ZSTD:
> +		ret = decompress_zstd(rctx, encoded_data, encoded_len,
> +				      unencoded_data, unencoded_len);
> +		if (ret)
> +			goto out;
> +		break;
> +	case BTRFS_ENCODED_IO_COMPRESSION_LZO_4K:
> +	case BTRFS_ENCODED_IO_COMPRESSION_LZO_8K:
> +	case BTRFS_ENCODED_IO_COMPRESSION_LZO_16K:
> +	case BTRFS_ENCODED_IO_COMPRESSION_LZO_32K:
> +	case BTRFS_ENCODED_IO_COMPRESSION_LZO_64K:
> +		page_shift = compression - BTRFS_ENCODED_IO_COMPRESSION_LZO_4K + 12;

Doesn't this calculation assume page size is 4k, what about arches with
larger page size (ppc/aarch64), shouldn't that '12' be adjusted?

> +		ret = decompress_lzo(encoded_data, encoded_len, unencoded_data,
> +				     unencoded_len, 1U << page_shift);
> +		if (ret)
> +			goto out;
> +		break;
> +	default:
> +		error("unknown compression: %d", compression);
> +		ret = -EOPNOTSUPP;
> +		goto out;
> +	}
> +
> +	pos = unencoded_offset;
> +	while (pos < unencoded_file_len) {
> +		w = pwrite(rctx->write_fd, unencoded_data + pos,
> +			   unencoded_file_len - pos, offset);
> +		if (w < 0) {
> +			ret = -errno;
> +			error("writing unencoded data failed: %m");
> +			goto out;
> +		}
> +		pos += w;
> +		offset += w;
> +	}
> +out:
> +	free(unencoded_data);
> +	return ret;
> +}
> +
>  static int process_encoded_write(const char *path, const void *data, u64 offset,
> -	u64 len, u64 unencoded_file_len, u64 unencoded_len,
> -	u64 unencoded_offset, u32 compression, u32 encryption, void *user)
> +				 u64 len, u64 unencoded_file_len,
> +				 u64 unencoded_len, u64 unencoded_offset,
> +				 u32 compression, u32 encryption, void *user)

That's irrelevant change for this patch,  it should be squashed in the
previous patch which introduces process_encoded_write.

>  {
>  	int ret;
>  	struct btrfs_receive *rctx = user;
> @@ -1007,6 +1230,7 @@ static int process_encoded_write(const char *path, const void *data, u64 offset,
>  		.compression = compression,
>  		.encryption = encryption,
>  	};
> +	bool encoded_write = !rctx->force_decompress;

No point in the local variable simply use !rctx->force_decompress in the
condition below.

>  
>  	if (encryption) {
>  		error("encoded_write: encryption not supported");
> @@ -1023,13 +1247,21 @@ static int process_encoded_write(const char *path, const void *data, u64 offset,
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = ioctl(rctx->write_fd, BTRFS_IOC_ENCODED_WRITE, &encoded);
> -	if (ret < 0) {
> -		ret = -errno;
> -		error("encoded_write: writing to %s failed: %m", path);
> -		return ret;
> +	if (encoded_write) {
> +		ret = ioctl(rctx->write_fd, BTRFS_IOC_ENCODED_WRITE, &encoded);
> +		if (ret >= 0)
> +			return 0;
> +		/* Fall back for these errors, fail hard for anything else. */
> +		if (errno != ENOSPC && errno != ENOTTY && errno != EINVAL) {
> +			ret = -errno;
> +			error("encoded_write: writing to %s failed: %m", path);
> +			return ret;
> +		}
>  	}
> -	return 0;
> +
> +	return decompress_and_write(rctx, data, offset, len, unencoded_file_len,
> +				    unencoded_len, unencoded_offset,
> +				    compression);
>  }
>  
>  static struct btrfs_send_ops send_ops = {

<snip>




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