On Thu, 01/26 11:04, Daniel P. Berrange wrote: > The -n arg to the convert command allows use of a pre-existing image, > rather than creating a new image. This adds a -n arg to the dd command > to get feature parity.
I remember there was a discussion about changing qemu-img dd's default to a "conv=nocreat" semantic, if so, "-n" might not be that useful. But that part hasn't made it into the tree, and I'm not sure which direction we should take. (Personally I think default to nocreat is a good idea). Fam > > Signed-off-by: Daniel P. Berrange <berra...@redhat.com> > --- > qemu-img-cmds.hx | 4 +-- > qemu-img.c | 79 > ++++++++++++++++++++++++++++++++++++-------------------- > qemu-img.texi | 7 ++++- > 3 files changed, 59 insertions(+), 31 deletions(-) > > diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx > index f054599..6732713 100644 > --- a/qemu-img-cmds.hx > +++ b/qemu-img-cmds.hx > @@ -46,9 +46,9 @@ STEXI > ETEXI > > DEF("dd", img_dd, > - "dd [--image-opts] [-f fmt] [-O output_fmt] [bs=block_size] > [count=blocks] [skip=blocks] if=input of=output") > + "dd [--image-opts] [-n] [-f fmt] [-O output_fmt] [bs=block_size] > [count=blocks] [skip=blocks] if=input of=output") > STEXI > -@item dd [--image-opts] [-f @var{fmt}] [-O @var{output_fmt}] > [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} > of=@var{output} > +@item dd [--image-opts] [-n] [-f @var{fmt}] [-O @var{output_fmt}] > [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} > of=@var{output} > ETEXI > > DEF("info", img_info, > diff --git a/qemu-img.c b/qemu-img.c > index 629f9e9..4d8d041 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -3917,10 +3917,10 @@ static int img_dd(int argc, char **argv) > QemuOptsList *create_opts = NULL; > Error *local_err = NULL; > bool image_opts = false; > - int c, i; > + int c, i, skip_create = 0; > const char *out_fmt = "raw"; > const char *fmt = NULL; > - int64_t size = 0; > + int64_t size = 0, out_size; > int64_t block_count = 0, out_pos, in_pos; > struct DdInfo dd = { > .flags = 0, > @@ -3954,7 +3954,7 @@ static int img_dd(int argc, char **argv) > { 0, 0, 0, 0 } > }; > > - while ((c = getopt_long(argc, argv, "hf:O:", long_options, NULL))) { > + while ((c = getopt_long(argc, argv, "hnf:O:", long_options, NULL))) { > if (c == EOF) { > break; > } > @@ -3965,6 +3965,9 @@ static int img_dd(int argc, char **argv) > case 'f': > fmt = optarg; > break; > + case 'n': > + skip_create = 1; > + break; > case '?': > error_report("Try 'qemu-img --help' for more information."); > ret = -1; > @@ -4051,22 +4054,25 @@ static int img_dd(int argc, char **argv) > ret = -1; > goto out; > } > - if (!drv->create_opts) { > - error_report("Format driver '%s' does not support image creation", > - drv->format_name); > - ret = -1; > - goto out; > - } > - if (!proto_drv->create_opts) { > - error_report("Protocol driver '%s' does not support image creation", > - proto_drv->format_name); > - ret = -1; > - goto out; > - } > - create_opts = qemu_opts_append(create_opts, drv->create_opts); > - create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); > > - opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); > + if (!skip_create) { > + if (!drv->create_opts) { > + error_report("Format driver '%s' does not support image > creation", > + drv->format_name); > + ret = -1; > + goto out; > + } > + if (!proto_drv->create_opts) { > + error_report("Protocol driver '%s' does not support image > creation", > + proto_drv->format_name); > + ret = -1; > + goto out; > + } > + create_opts = qemu_opts_append(create_opts, drv->create_opts); > + create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); > + > + opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); > + } > > size = blk_getlength(blk1); > if (size < 0) { > @@ -4083,19 +4089,22 @@ static int img_dd(int argc, char **argv) > /* Overflow means the specified offset is beyond input image's size */ > if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz || > size < in.bsz * in.offset)) { > - qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort); > + out_size = 0; > } else { > - qemu_opt_set_number(opts, BLOCK_OPT_SIZE, > - size - in.bsz * in.offset, &error_abort); > + out_size = size - in.bsz * in.offset; > } > > - ret = bdrv_create(drv, out.filename, opts, &local_err); > - if (ret < 0) { > - error_reportf_err(local_err, > - "%s: error while creating output image: ", > - out.filename); > - ret = -1; > - goto out; > + if (!skip_create) { > + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, out_size, &error_abort); > + > + ret = bdrv_create(drv, out.filename, opts, &local_err); > + if (ret < 0) { > + error_reportf_err(local_err, > + "%s: error while creating output image: ", > + out.filename); > + ret = -1; > + goto out; > + } > } > > /* TODO, we can't honour --image-opts for the target, > @@ -4111,6 +4120,20 @@ static int img_dd(int argc, char **argv) > goto out; > } > > + if (skip_create) { > + int64_t existing_size = blk_getlength(blk2); > + if (existing_size < 0) { > + error_report("unable to get output image length: %s", > + strerror(-existing_size)); > + ret = -1; > + goto out; > + } else if (existing_size < out_size) { > + error_report("output file is smaller than input data length"); > + ret = -1; > + goto out; > + } > + } > + > if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz || > size < in.offset * in.bsz)) { > /* We give a warning if the skip option is bigger than the input > diff --git a/qemu-img.texi b/qemu-img.texi > index 174aae3..b952d6a 100644 > --- a/qemu-img.texi > +++ b/qemu-img.texi > @@ -326,7 +326,7 @@ skipped. This is useful for formats such as @code{rbd} if > the target > volume has already been created with site specific options that cannot > be supplied through qemu-img. > > -@item dd [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] > [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output} > +@item dd [-n] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] > [count=@var{blocks}] [skip=@var{blocks}] if=@var{input} of=@var{output} > > Dd copies from @var{input} file to @var{output} file converting it from > @var{fmt} format to @var{output_fmt} format. > @@ -337,6 +337,11 @@ dd will stop reading input after reading @var{blocks} > input blocks. > > The size syntax is similar to dd(1)'s size syntax. > > +If the @code{-n} option is specified, the target volume creation will be > +skipped. This is useful for formats such as @code{rbd} if the target > +volume has already been created with site specific options that cannot > +be supplied through qemu-img. > + > @item info [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] > @var{filename} > > Give information about the disk image @var{filename}. Use it in > -- > 2.9.3 > >