1 files changed, 415 insertions, 0 deletions
diff --git a/drivers/md/dm-vdo/indexer/io-factory.c b/drivers/md/dm-vdo/indexer/io-factory.c
new file mode 100644
index 000000000000..515765d35794
--- /dev/null
+++ b/drivers/md/dm-vdo/indexer/io-factory.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "io-factory.h"
+
+#include <linux/atomic.h>
+#include <linux/blkdev.h>
+#include <linux/err.h>
+#include <linux/mount.h>
+
+#include "logger.h"
+#include "memory-alloc.h"
+#include "numeric.h"
+
+/*
+ * The I/O factory object manages access to index storage, which is a contiguous range of blocks on
+ * a block device.
+ *
+ * The factory holds the open device and is responsible for closing it. The factory has methods to
+ * make helper structures that can be used to access sections of the index.
+ */
+struct io_factory {
+	struct block_device *bdev;
+	atomic_t ref_count;
+};
+
+/* The buffered reader allows efficient I/O by reading page-sized segments into a buffer. */
+struct buffered_reader {
+	struct io_factory *factory;
+	struct dm_bufio_client *client;
+	struct dm_buffer *buffer;
+	sector_t limit;
+	sector_t block_number;
+	u8 *start;
+	u8 *end;
+};
+
+#define MAX_READ_AHEAD_BLOCKS 4
+
+/*
+ * The buffered writer allows efficient I/O by buffering writes and committing page-sized segments
+ * to storage.
+ */
+struct buffered_writer {
+	struct io_factory *factory;
+	struct dm_bufio_client *client;
+	struct dm_buffer *buffer;
+	sector_t limit;
+	sector_t block_number;
+	u8 *start;
+	u8 *end;
+	int error;
+};
+
+static void uds_get_io_factory(struct io_factory *factory)
+{
+	atomic_inc(&factory->ref_count);
+}
+
+int uds_make_io_factory(struct block_device *bdev, struct io_factory **factory_ptr)
+{
+	int result;
+	struct io_factory *factory;
+
+	result = vdo_allocate(1, struct io_factory, __func__, &factory);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	factory->bdev = bdev;
+	atomic_set_release(&factory->ref_count, 1);
+
+	*factory_ptr = factory;
+	return UDS_SUCCESS;
+}
+
+int uds_replace_storage(struct io_factory *factory, struct block_device *bdev)
+{
+	factory->bdev = bdev;
+	return UDS_SUCCESS;
+}
+
+/* Free an I/O factory once all references have been released. */
+void uds_put_io_factory(struct io_factory *factory)
+{
+	if (atomic_add_return(-1, &factory->ref_count) <= 0)
+		vdo_free(factory);
+}
+
+size_t uds_get_writable_size(struct io_factory *factory)
+{
+	return i_size_read(factory->bdev->bd_inode);
+}
+
+/* Create a struct dm_bufio_client for an index region starting at offset. */
+int uds_make_bufio(struct io_factory *factory, off_t block_offset, size_t block_size,
+		   unsigned int reserved_buffers, struct dm_bufio_client **client_ptr)
+{
+	struct dm_bufio_client *client;
+
+	client = dm_bufio_client_create(factory->bdev, block_size, reserved_buffers, 0,
+					NULL, NULL, 0);
+	if (IS_ERR(client))
+		return -PTR_ERR(client);
+
+	dm_bufio_set_sector_offset(client, block_offset * SECTORS_PER_BLOCK);
+	*client_ptr = client;
+	return UDS_SUCCESS;
+}
+
+static void read_ahead(struct buffered_reader *reader, sector_t block_number)
+{
+	if (block_number < reader->limit) {
+		sector_t read_ahead = min((sector_t) MAX_READ_AHEAD_BLOCKS,
+					  reader->limit - block_number);
+
+		dm_bufio_prefetch(reader->client, block_number, read_ahead);
+	}
+}
+
+void uds_free_buffered_reader(struct buffered_reader *reader)
+{
+	if (reader == NULL)
+		return;
+
+	if (reader->buffer != NULL)
+		dm_bufio_release(reader->buffer);
+
+	dm_bufio_client_destroy(reader->client);
+	uds_put_io_factory(reader->factory);
+	vdo_free(reader);
+}
+
+/* Create a buffered reader for an index region starting at offset. */
+int uds_make_buffered_reader(struct io_factory *factory, off_t offset, u64 block_count,
+			     struct buffered_reader **reader_ptr)
+{
+	int result;
+	struct dm_bufio_client *client = NULL;
+	struct buffered_reader *reader = NULL;
+
+	result = uds_make_bufio(factory, offset, UDS_BLOCK_SIZE, 1, &client);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	result = vdo_allocate(1, struct buffered_reader, "buffered reader", &reader);
+	if (result != VDO_SUCCESS) {
+		dm_bufio_client_destroy(client);
+		return result;
+	}
+
+	*reader = (struct buffered_reader) {
+		.factory = factory,
+		.client = client,
+		.buffer = NULL,
+		.limit = block_count,
+		.block_number = 0,
+		.start = NULL,
+		.end = NULL,
+	};
+
+	read_ahead(reader, 0);
+	uds_get_io_factory(factory);
+	*reader_ptr = reader;
+	return UDS_SUCCESS;
+}
+
+static int position_reader(struct buffered_reader *reader, sector_t block_number,
+			   off_t offset)
+{
+	struct dm_buffer *buffer = NULL;
+	void *data;
+
+	if ((reader->end == NULL) || (block_number != reader->block_number)) {
+		if (block_number >= reader->limit)
+			return UDS_OUT_OF_RANGE;
+
+		if (reader->buffer != NULL)
+			dm_bufio_release(vdo_forget(reader->buffer));
+
+		data = dm_bufio_read(reader->client, block_number, &buffer);
+		if (IS_ERR(data))
+			return -PTR_ERR(data);
+
+		reader->buffer = buffer;
+		reader->start = data;
+		if (block_number == reader->block_number + 1)
+			read_ahead(reader, block_number + 1);
+	}
+
+	reader->block_number = block_number;
+	reader->end = reader->start + offset;
+	return UDS_SUCCESS;
+}
+
+static size_t bytes_remaining_in_read_buffer(struct buffered_reader *reader)
+{
+	return (reader->end == NULL) ? 0 : reader->start + UDS_BLOCK_SIZE - reader->end;
+}
+
+static int reset_reader(struct buffered_reader *reader)
+{
+	sector_t block_number;
+
+	if (bytes_remaining_in_read_buffer(reader) > 0)
+		return UDS_SUCCESS;
+
+	block_number = reader->block_number;
+	if (reader->end != NULL)
+		block_number++;
+
+	return position_reader(reader, block_number, 0);
+}
+
+int uds_read_from_buffered_reader(struct buffered_reader *reader, u8 *data,
+				  size_t length)
+{
+	int result = UDS_SUCCESS;
+	size_t chunk_size;
+
+	while (length > 0) {
+		result = reset_reader(reader);
+		if (result != UDS_SUCCESS)
+			return result;
+
+		chunk_size = min(length, bytes_remaining_in_read_buffer(reader));
+		memcpy(data, reader->end, chunk_size);
+		length -= chunk_size;
+		data += chunk_size;
+		reader->end += chunk_size;
+	}
+
+	return UDS_SUCCESS;
+}
+
+/*
+ * Verify that the next data on the reader matches the required value. If the value matches, the
+ * matching contents are consumed. If the value does not match, the reader state is unchanged.
+ */
+int uds_verify_buffered_data(struct buffered_reader *reader, const u8 *value,
+			     size_t length)
+{
+	int result = UDS_SUCCESS;
+	size_t chunk_size;
+	sector_t start_block_number = reader->block_number;
+	int start_offset = reader->end - reader->start;
+
+	while (length > 0) {
+		result = reset_reader(reader);
+		if (result != UDS_SUCCESS) {
+			result = UDS_CORRUPT_DATA;
+			break;
+		}
+
+		chunk_size = min(length, bytes_remaining_in_read_buffer(reader));
+		if (memcmp(value, reader->end, chunk_size) != 0) {
+			result = UDS_CORRUPT_DATA;
+			break;
+		}
+
+		length -= chunk_size;
+		value += chunk_size;
+		reader->end += chunk_size;
+	}
+
+	if (result != UDS_SUCCESS)
+		position_reader(reader, start_block_number, start_offset);
+
+	return result;
+}
+
+/* Create a buffered writer for an index region starting at offset. */
+int uds_make_buffered_writer(struct io_factory *factory, off_t offset, u64 block_count,
+			     struct buffered_writer **writer_ptr)
+{
+	int result;
+	struct dm_bufio_client *client = NULL;
+	struct buffered_writer *writer;
+
+	result = uds_make_bufio(factory, offset, UDS_BLOCK_SIZE, 1, &client);
+	if (result != UDS_SUCCESS)
+		return result;
+
+	result = vdo_allocate(1, struct buffered_writer, "buffered writer", &writer);
+	if (result != VDO_SUCCESS) {
+		dm_bufio_client_destroy(client);
+		return result;
+	}
+
+	*writer = (struct buffered_writer) {
+		.factory = factory,
+		.client = client,
+		.buffer = NULL,
+		.limit = block_count,
+		.start = NULL,
+		.end = NULL,
+		.block_number = 0,
+		.error = UDS_SUCCESS,
+	};
+
+	uds_get_io_factory(factory);
+	*writer_ptr = writer;
+	return UDS_SUCCESS;
+}
+
+static size_t get_remaining_write_space(struct buffered_writer *writer)
+{
+	return writer->start + UDS_BLOCK_SIZE - writer->end;
+}
+
+static int __must_check prepare_next_buffer(struct buffered_writer *writer)
+{
+	struct dm_buffer *buffer = NULL;
+	void *data;
+
+	if (writer->block_number >= writer->limit) {
+		writer->error = UDS_OUT_OF_RANGE;
+		return UDS_OUT_OF_RANGE;
+	}
+
+	data = dm_bufio_new(writer->client, writer->block_number, &buffer);
+	if (IS_ERR(data)) {
+		writer->error = -PTR_ERR(data);
+		return writer->error;
+	}
+
+	writer->buffer = buffer;
+	writer->start = data;
+	writer->end = data;
+	return UDS_SUCCESS;
+}
+
+static int flush_previous_buffer(struct buffered_writer *writer)
+{
+	size_t available;
+
+	if (writer->buffer == NULL)
+		return writer->error;
+
+	if (writer->error == UDS_SUCCESS) {
+		available = get_remaining_write_space(writer);
+
+		if (available > 0)
+			memset(writer->end, 0, available);
+
+		dm_bufio_mark_buffer_dirty(writer->buffer);
+	}
+
+	dm_bufio_release(writer->buffer);
+	writer->buffer = NULL;
+	writer->start = NULL;
+	writer->end = NULL;
+	writer->block_number++;
+	return writer->error;
+}
+
+void uds_free_buffered_writer(struct buffered_writer *writer)
+{
+	int result;
+
+	if (writer == NULL)
+		return;
+
+	flush_previous_buffer(writer);
+	result = -dm_bufio_write_dirty_buffers(writer->client);
+	if (result != UDS_SUCCESS)
+		vdo_log_warning_strerror(result, "%s: failed to sync storage", __func__);
+
+	dm_bufio_client_destroy(writer->client);
+	uds_put_io_factory(writer->factory);
+	vdo_free(writer);
+}
+
+/*
+ * Append data to the buffer, writing as needed. If no data is provided, zeros are written instead.
+ * If a write error occurs, it is recorded and returned on every subsequent write attempt.
+ */
+int uds_write_to_buffered_writer(struct buffered_writer *writer, const u8 *data,
+				 size_t length)
+{
+	int result = writer->error;
+	size_t chunk_size;
+
+	while ((length > 0) && (result == UDS_SUCCESS)) {
+		if (writer->buffer == NULL) {
+			result = prepare_next_buffer(writer);
+			continue;
+		}
+
+		chunk_size = min(length, get_remaining_write_space(writer));
+		if (data == NULL) {
+			memset(writer->end, 0, chunk_size);
+		} else {
+			memcpy(writer->end, data, chunk_size);
+			data += chunk_size;
+		}
+
+		length -= chunk_size;
+		writer->end += chunk_size;
+
+		if (get_remaining_write_space(writer) == 0)
+			result = uds_flush_buffered_writer(writer);
+	}
+
+	return result;
+}
+
+int uds_flush_buffered_writer(struct buffered_writer *writer)
+{
+	if (writer->error != UDS_SUCCESS)
+		return writer->error;
+
+	return flush_previous_buffer(writer);
+}