diff options
| -rw-r--r-- | block.c | 27 | ||||
| -rw-r--r-- | block.h | 2 | ||||
| -rw-r--r-- | qemu-img.c | 47 | ||||
| -rw-r--r-- | qemu-img.texi | 8 |
4 files changed, 76 insertions, 8 deletions
@@ -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) { @@ -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 diff --git a/qemu-img.c b/qemu-img.c index 309a746da7..f9d8b7d99b 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -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; @@ -415,6 +430,9 @@ static int img_convert(int argc, char **argv) if (bs_n < 1) help(); 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) @@ -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"); } diff --git a/qemu-img.texi b/qemu-img.texi index 44c4de8743..1c0504bcfa 100644 --- a/qemu-img.texi +++ b/qemu-img.texi @@ -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: |