bcachefs-tools/c_src/qcow2.c

#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

#include "qcow2.h"
#include "tools-util.h"

#define QCOW_MAGIC		(('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
#define QCOW_VERSION		2
#define QCOW_OFLAG_COPIED	(1LL << 63)

struct qcow2_hdr {
	u32			magic;
	u32			version;

	u64			backing_file_offset;
	u32			backing_file_size;

	u32			block_bits;
	u64			size;
	u32			crypt_method;

	u32			l1_size;
	u64			l1_table_offset;

	u64			refcount_table_offset;
	u32			refcount_table_blocks;

	u32			nb_snapshots;
	u64			snapshots_offset;
};

static void __qcow2_write_buf(struct qcow2_image *img, void *buf, unsigned len)
{
	assert(!(len % img->block_size));

	xpwrite(img->outfd, buf, len, img->offset, "qcow2 data");
	img->offset += len;
}

static void flush_l2(struct qcow2_image *img)
{
	if (img->l1_index != -1) {
		img->l1_table[img->l1_index] =
			cpu_to_be64(img->offset|QCOW_OFLAG_COPIED);

		__qcow2_write_buf(img, img->l2_table, img->block_size);

		memset(img->l2_table, 0, img->block_size);
		img->l1_index = -1;
	}
}

static void add_l2(struct qcow2_image *img, u64 src_blk, u64 dst_offset)
{
	unsigned l2_size = img->block_size / sizeof(u64);
	u64 l1_index = src_blk / l2_size;
	u64 l2_index = src_blk & (l2_size - 1);

	if (img->l1_index != l1_index) {
		flush_l2(img);
		img->l1_index = l1_index;
	}

	img->l2_table[l2_index] = cpu_to_be64(dst_offset|QCOW_OFLAG_COPIED);
}

void qcow2_write_buf(struct qcow2_image *img, void *buf, unsigned len, u64 src_offset)
{
	u64 dst_offset = img->offset;
	__qcow2_write_buf(img, buf, len);

	while (len) {
		add_l2(img, src_offset / img->block_size, dst_offset);
		dst_offset += img->block_size;
		src_offset += img->block_size;
		len -= img->block_size;
	}
}

void qcow2_write_ranges(struct qcow2_image *img, ranges *data)
{
	ranges_roundup(data, img->block_size);
	ranges_sort_merge(data);

	char *buf = xmalloc(img->block_size);

	/* Write data: */
	darray_for_each(*data, r)
		for (u64 src_offset = r->start;
		     src_offset < r->end;
		     src_offset += img->block_size) {
			xpread(img->infd, buf, img->block_size, src_offset);
			qcow2_write_buf(img, buf, img->block_size, src_offset);
		}

	free(buf);
}

void qcow2_image_init(struct qcow2_image *img, int infd, int outfd, unsigned block_size)
{
	assert(is_power_of_2(block_size));

	u64 image_size = get_size(infd);
	unsigned l2_size = block_size / sizeof(u64);
	unsigned l1_size = DIV_ROUND_UP(image_size, (u64) block_size * l2_size);

	*img = (struct qcow2_image) {
		.infd		= infd,
		.outfd		= outfd,
		.image_size	= image_size,
		.block_size	= block_size,
		.l1_size	= l1_size,
		.l1_table	= xcalloc(l1_size, sizeof(u64)),
		.l1_index	= -1,
		.l2_table	= xcalloc(l2_size, sizeof(u64)),
		.offset		= round_up(sizeof(struct qcow2_hdr), block_size),
	};
}

void qcow2_image_finish(struct qcow2_image *img)
{
	char *buf = xmalloc(img->block_size);

	flush_l2(img);

	/* Write L1 table: */
	u64 dst_offset		= img->offset;
	img->offset		+= round_up(img->l1_size * sizeof(u64), img->block_size);
	xpwrite(img->outfd, img->l1_table, img->l1_size * sizeof(u64), dst_offset,
		"qcow2 l1 table");

	/* Write header: */
	struct qcow2_hdr hdr = {
		.magic			= cpu_to_be32(QCOW_MAGIC),
		.version		= cpu_to_be32(QCOW_VERSION),
		.block_bits		= cpu_to_be32(ilog2(img->block_size)),
		.size			= cpu_to_be64(img->image_size),
		.l1_size		= cpu_to_be32(img->l1_size),
		.l1_table_offset	= cpu_to_be64(dst_offset),
	};

	memset(buf, 0, img->block_size);
	memcpy(buf, &hdr, sizeof(hdr));
	xpwrite(img->outfd, buf, img->block_size, 0, "qcow2 header");

	free(img->l2_table);
	free(img->l1_table);
	free(buf);
}

void qcow2_write_image(int infd, int outfd, ranges *data,
		       unsigned block_size)
{
	struct qcow2_image img;

	qcow2_image_init(&img, infd, outfd, block_size);
	qcow2_write_ranges(&img, data);
	qcow2_image_finish(&img);
}

void qcow2_to_raw(int infd, int outfd)
{
	struct qcow2_hdr hdr;

	xpread(infd, &hdr, sizeof(hdr), 0);

	if (hdr.magic != cpu_to_be32(QCOW_MAGIC))
		die("not a qcow2 image");

	if (hdr.version != cpu_to_be32(QCOW_VERSION))
		die("incorrect qcow2 version");

	ftruncate(outfd, be64_to_cpu(hdr.size));

	unsigned block_size = 1U << be32_to_cpu(hdr.block_bits);

	unsigned l1_size = be32_to_cpu(hdr.l1_size);
	unsigned l2_size = block_size / sizeof(u64);

	__be64 *l1_table	= xcalloc(l1_size, sizeof(u64));
	__be64 *l2_table	= xmalloc(block_size);
	void *data_buf		= xmalloc(block_size);

	xpread(infd, l1_table, l1_size * sizeof(u64), be64_to_cpu(hdr.l1_table_offset));

	for (u64 i = 0; i < l1_size; i++) {
		if (!l1_table[i])
			continue;

		xpread(infd, l2_table, block_size, be64_to_cpu(l1_table[i]) & ~QCOW_OFLAG_COPIED);

		for (unsigned j = 0; j < l2_size; j++) {
			u64 src_offset = be64_to_cpu(l2_table[j]) & ~QCOW_OFLAG_COPIED;
			if (!src_offset)
				continue;

			u64 dst_offset = (i * l2_size + j) * block_size;

			xpread(infd,	data_buf, block_size, src_offset);
			xpwrite(outfd,	data_buf, block_size, dst_offset, "qcow2 data");
		}
	}

	free(data_buf);
	free(l2_table);
	free(l1_table);
}