New qemu-img convert -B option, by Marc Bevand. (f58c7b35) · Commits · SUMMER2020 / students / proj-2021291

block.c

+27 −0

Original line number	Diff line number	Diff line
		@@ -884,6 +884,33 @@ void bdrv_flush(BlockDriverState *bs)
		bdrv_flush(bs->backing_hd);
		}

		/*
		* Returns true iff the specified sector is present in the disk image. Drivers
		* not implementing the functionality are assumed to not support backing files,
		* hence all their sectors are reported as allocated.
		*
		* 'pnum' is set to the number of sectors (including and immediately following
		* the specified sector) that are known to be in the same
		* allocated/unallocated state.
		*
		* 'nb_sectors' is the max value 'pnum' should be set to.
		*/
		int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
		int *pnum)
		{
		int64_t n;
		if (!bs->drv->bdrv_is_allocated) {
		if (sector_num >= bs->total_sectors) {
		*pnum = 0;
		return 0;
		}
		n = bs->total_sectors - sector_num;
		*pnum = (n < nb_sectors) ? (n) : (nb_sectors);
		return 1;
		}
		return bs->drv->bdrv_is_allocated(bs, sector_num, nb_sectors, pnum);
		}

		#ifndef QEMU_IMG
		void bdrv_info(void)
		{

block.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -99,6 +99,8 @@ int qemu_key_check(BlockDriverState bs, const char name);

		/* Ensure contents are flushed to disk. */
		void bdrv_flush(BlockDriverState *bs);
		int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
		int *pnum);

		#define BDRV_TYPE_HD 0
		#define BDRV_TYPE_CDROM 1

qemu-img.c

+41 −6

Original line number	Diff line number	Diff line
		@@ -55,13 +55,17 @@ static void help(void)
		"Command syntax:\n"
		" create [-e] [-6] [-b base_image] [-f fmt] filename [size]\n"
		" commit [-f fmt] filename\n"
		" convert [-c] [-e] [-6] [-f fmt] [-O output_fmt] filename [filename2 [...]] output_filename\n"
		" convert [-c] [-e] [-6] [-f fmt] [-O output_fmt] [-B output_base_image] filename [filename2 [...]] output_filename\n"
		" info [-f fmt] filename\n"
		"\n"
		"Command parameters:\n"
		" 'filename' is a disk image filename\n"
		" 'base_image' is the read-only disk image which is used as base for a copy on\n"
		" write image; the copy on write image only stores the modified data\n"
		" 'output_base_image' forces the output image to be created as a copy on write\n"
		" image of the specified base image; 'output_base_image' should have the same\n"
		" content as the input's base image, however the path, image format, etc may\n"
		" differ\n"
		" 'fmt' is the disk image format. It is guessed automatically in most cases\n"
		" 'size' is the disk image size in kilobytes. Optional suffixes 'M' (megabyte)\n"
		" and 'G' (gigabyte) are supported\n"
		@@ -350,6 +354,13 @@ static int is_not_zero(const uint8_t *sector, int len)
		return 0;
		}

		/*
		* Returns true iff the first sector pointed to by 'buf' contains at least
		* a non-NUL byte.
		*
		* 'pnum' is set to the number of sectors (including and immediately following
		* the first one) that are known to be in the same allocated/unallocated state.
		*/
		static int is_allocated_sectors(const uint8_t buf, int n, int pnum)
		{
		int v, i;
		@@ -373,7 +384,7 @@ static int is_allocated_sectors(const uint8_t buf, int n, int pnum)
		static int img_convert(int argc, char **argv)
		{
		int c, ret, n, n1, bs_n, bs_i, flags, cluster_size, cluster_sectors;
		const char fmt, out_fmt, *out_filename;
		const char fmt, out_fmt, out_baseimg, out_filename;
		BlockDriver *drv;
		BlockDriverState *bs, out_bs;
		int64_t total_sectors, nb_sectors, sector_num, bs_offset;
		@@ -384,9 +395,10 @@ static int img_convert(int argc, char **argv)

		fmt = NULL;
		out_fmt = "raw";
		out_baseimg = NULL;
		flags = 0;
		for(;;) {
		c = getopt(argc, argv, "f:O:hce6");
		c = getopt(argc, argv, "f:O:B:hce6");
		if (c == -1)
		break;
		switch(c) {
		@@ -399,6 +411,9 @@ static int img_convert(int argc, char **argv)
		case 'O':
		out_fmt = optarg;
		break;
		case 'B':
		out_baseimg = optarg;
		break;
		case 'c':
		flags \|= BLOCK_FLAG_COMPRESS;
		break;
		@@ -416,6 +431,9 @@ static int img_convert(int argc, char **argv)

		out_filename = argv[argc - 1];

		if (bs_n > 1 && out_baseimg)
		error("-B makes no sense when concatenating multiple input images");

		bs = calloc(bs_n, sizeof(BlockDriverState *));
		if (!bs)
		error("Out of memory");
		@@ -441,7 +459,7 @@ static int img_convert(int argc, char **argv)
		if (flags & BLOCK_FLAG_ENCRYPT && flags & BLOCK_FLAG_COMPRESS)
		error("Compression and encryption not supported at the same time");

		ret = bdrv_create(drv, out_filename, total_sectors, NULL, flags);
		ret = bdrv_create(drv, out_filename, total_sectors, out_baseimg, flags);
		if (ret < 0) {
		if (ret == -ENOTSUP) {
		error("Formatting not supported for file format '%s'", fmt);
		@@ -520,7 +538,7 @@ static int img_convert(int argc, char **argv)
		/* signal EOF to align */
		bdrv_write_compressed(out_bs, 0, NULL, 0);
		} else {
		sector_num = 0;
		sector_num = 0; // total number of sectors converted so far
		for(;;) {
		nb_sectors = total_sectors - sector_num;
		if (nb_sectors <= 0)
		@@ -543,6 +561,20 @@ static int img_convert(int argc, char **argv)
		if (n > bs_offset + bs_sectors - sector_num)
		n = bs_offset + bs_sectors - sector_num;

		/* If the output image is being created as a copy on write image,
		assume that sectors which are unallocated in the input image
		are present in both the output's and input's base images (no
		need to copy them). */
		if (out_baseimg) {
		if (!bdrv_is_allocated(bs[bs_i], sector_num - bs_offset, n, &n1)) {
		sector_num += n1;
		continue;
		}
		/* The next 'n1' sectors are allocated in the input image. Copy
		only those as they may be followed by unallocated sectors. */
		n = n1;
		}

		if (bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n) < 0)
		error("error while reading");
		/* NOTE: at the same time we convert, we do not write zero
		@@ -550,7 +582,10 @@ static int img_convert(int argc, char **argv)
		should add a specific call to have the info to go faster */
		buf1 = buf;
		while (n > 0) {
		if (is_allocated_sectors(buf1, n, &n1)) {
		/* If the output image is being created as a copy on write image,
		copy all sectors even the ones containing only NUL bytes,
		because they may differ from the sectors in the base image. */
		if (out_baseimg \|\| is_allocated_sectors(buf1, n, &n1)) {
		if (bdrv_write(out_bs, sector_num, buf1, n1) < 0)
		error("error while writing");
		}

qemu-img.texi

+6 −2

Original line number	Diff line number	Diff line
		@@ -10,7 +10,7 @@ The following commands are supported:
		@table @option
		@item create [-e] [-6] [-b @var{base_image}] [-f @var{fmt}] @var{filename} [@var{size}]
		@item commit [-f @var{fmt}] @var{filename}
		@item convert [-c] [-e] [-6] [-f @var{fmt}] [-O @var{output_fmt}] @var{filename} [@var{filename2} [...]] @var{output_filename}
		@item convert [-c] [-e] [-6] [-f @var{fmt}] [-O @var{output_fmt}] [-B @var{output_base_image}] @var{filename} [@var{filename2} [...]] @var{output_filename}
		@item info [-f @var{fmt}] @var{filename}
		@end table

		@@ -21,7 +21,11 @@ Command parameters:
		@item base_image
		is the read-only disk image which is used as base for a copy on
		write image; the copy on write image only stores the modified data

		@item output_base_image
		forces the output image to be created as a copy on write
		image of the specified base image; @code{output_base_image} should have the same
		content as the input's base image, however the path, image format, etc may
		differ
		@item fmt
		is the disk image format. It is guessed automatically in most cases. The following formats are supported: