dm-vdo/indexer/io-factory.c

29 /* The buffered reader allows efficient I/O by reading page-sized segments into a buffer. */
112 static void read_ahead(struct buffered_reader *reader, sector_t block_number)
114 	if (block_number < reader->limit) {
116 					  reader->limit - block_number);
118 		dm_bufio_prefetch(reader->client, block_number, read_ahead);
122 void uds_free_buffered_reader(struct buffered_reader *reader)
124 	if (reader == NULL)
127 	if (reader->buffer != NULL)
128 		dm_bufio_release(reader->buffer);
130 	dm_bufio_client_destroy(reader->client);
131 	uds_put_io_factory(reader->factory);
132 	vdo_free(reader);
135 /* Create a buffered reader for an index region starting at offset. */
141 	struct buffered_reader *reader = NULL;
147 	result = vdo_allocate(1, struct buffered_reader, "buffered reader", &reader);
153 	*reader = (struct buffered_reader) {
163 	read_ahead(reader, 0);
165 	*reader_ptr = reader;
169 static int position_reader(struct buffered_reader *reader, sector_t block_number,
175 	if ((reader->end == NULL) || (block_number != reader->block_number)) {
176 		if (block_number >= reader->limit)
179 		if (reader->buffer != NULL)
180 			dm_bufio_release(vdo_forget(reader->buffer));
182 		data = dm_bufio_read(reader->client, block_number, &buffer);
186 		reader->buffer = buffer;
187 		reader->start = data;
188 		if (block_number == reader->block_number + 1)
189 			read_ahead(reader, block_number + 1);
192 	reader->block_number = block_number;
193 	reader->end = reader->start + offset;
197 static size_t bytes_remaining_in_read_buffer(struct buffered_reader *reader)
199 	return (reader->end == NULL) ? 0 : reader->start + UDS_BLOCK_SIZE - reader->end;
202 static int reset_reader(struct buffered_reader *reader)
206 	if (bytes_remaining_in_read_buffer(reader) > 0)
209 	block_number = reader->block_number;
210 	if (reader->end != NULL)
213 	return position_reader(reader, block_number, 0);
216 int uds_read_from_buffered_reader(struct buffered_reader *reader, u8 *data,
223 		result = reset_reader(reader);
227 		chunk_size = min(length, bytes_remaining_in_read_buffer(reader));
228 		memcpy(data, reader->end, chunk_size);
231 		reader->end += chunk_size;
238  * Verify that the next data on the reader matches the required value. If the value matches, the
239  * matching contents are consumed. If the value does not match, the reader state is unchanged.
241 int uds_verify_buffered_data(struct buffered_reader *reader, const u8 *value,
246 	sector_t start_block_number = reader->block_number;
247 	int start_offset = reader->end - reader->start;
250 		result = reset_reader(reader);
256 		chunk_size = min(length, bytes_remaining_in_read_buffer(reader));
257 		if (memcmp(value, reader->end, chunk_size) != 0) {
264 		reader->end += chunk_size;
268 		position_reader(reader, start_block_number, start_offset);