Re: [Qemu-devel] [PATCH] qemu-img: add conv=notrunc option to dd

[Fam Zheng <famz@redhat.com>]

On Thu, 08/11 05:07, Reda Sallahi wrote:
> This adds the conv=notrunc option to dd which tells dd to not truncate the
> output.
> 
> For the time being we make it mandatory to specify conv=notrunc.
> 
> Signed-off-by: Reda Sallahi <fullmanet@gmail.com>
> ---
>  qemu-img-cmds.hx       |  4 ++--
>  qemu-img.c             | 31 ++++++++++++++++++++++++++++---
>  qemu-img.texi          | 15 +++++++++------
>  tests/qemu-iotests/158 |  2 +-
>  tests/qemu-iotests/159 |  3 ++-
>  tests/qemu-iotests/160 |  7 ++++---
>  6 files changed, 46 insertions(+), 16 deletions(-)
> 
> diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
> index f054599..18685ac 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] [-f fmt] [-O output_fmt] [bs=block_size] [count=blocks] [skip=blocks] [conv=notrunc] 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] [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] [conv=notrunc] if=@var{input} of=@var{output}
>  ETEXI
>  
>  DEF("info", img_info,
> diff --git a/qemu-img.c b/qemu-img.c
> index 3adec86..16b56b8 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -174,7 +174,8 @@ static void QEMU_NORETURN help(void)
>             "  'count=N' copy only N input blocks\n"
>             "  'if=FILE' read from FILE\n"
>             "  'of=FILE' write to FILE\n"
> -           "  'skip=N' skip N bs-sized blocks at the start of input\n";
> +           "  'skip=N' skip N bs-sized blocks at the start of input\n"
> +           "  'conv=notrunc' do not truncate the output file\n";
>  
>      printf("%s\nSupported formats:", help_msg);
>      bdrv_iterate_format(format_print, NULL);
> @@ -3807,10 +3808,12 @@ out:
>  #define C_IF      04
>  #define C_OF      010
>  #define C_SKIP    020
> +#define C_CONV    040
>  
>  struct DdInfo {
>      unsigned int flags;
>      int64_t count;
> +    unsigned int conv;
>  };
>  
>  struct DdIo {
> @@ -3894,6 +3897,21 @@ static int img_dd_skip(const char *arg,
>      return 0;
>  }
>  
> +#define C_NOTRUNC 01
> +
> +static int img_dd_conv(const char *arg,
> +                       struct DdIo *in, struct DdIo *out,
> +                       struct DdInfo *dd)
> +{
> +    if (!strcmp(arg, "notrunc")) {
> +        dd->conv |= C_NOTRUNC;
> +        return 0;
> +    } else {
> +        error_report("invalid conversion: '%s'", arg);
> +        return 1;
> +    }
> +}
> +
>  static int img_dd(int argc, char **argv)
>  {
>      int ret = 0;
> @@ -3909,10 +3927,11 @@ static int img_dd(int argc, char **argv)
>      const char *out_fmt = "raw";
>      const char *fmt = NULL;
>      int64_t size = 0;
> -    int64_t block_count = 0, out_pos, in_pos;
> +    int64_t out_pos, in_pos;

This change is not related to this patch. It should probably done by another
patch, or removed.

>      struct DdInfo dd = {
>          .flags = 0,
>          .count = 0,
> +        .conv = 0
>      };
>      struct DdIo in = {
>          .bsz = 512, /* Block size is by default 512 bytes */
> @@ -3933,6 +3952,7 @@ static int img_dd(int argc, char **argv)
>          { "if", img_dd_if, C_IF },
>          { "of", img_dd_of, C_OF },
>          { "skip", img_dd_skip, C_SKIP },
> +        { "conv", img_dd_conv, C_CONV },
>          { NULL, NULL, 0 }
>      };
>      const struct option long_options[] = {
> @@ -3997,6 +4017,11 @@ static int img_dd(int argc, char **argv)
>          g_free(arg);
>          arg = NULL;
>      }
> +    if (!(dd.conv & C_NOTRUNC)) {
> +        error_report("conv=notrunc not specified");

A comment and/or a more detailed error message explaining the situation why we
do this now would be necessary, so that in the future we'll remember to do the
right thing once it's decided.

> +        ret = -1;
> +        goto out;
> +    }
>  
>      if (!(dd.flags & C_IF && dd.flags & C_OF)) {
>          error_report("Must specify both input and output files");
> @@ -4091,7 +4116,7 @@ static int img_dd(int argc, char **argv)
>  
>      in.buf = g_new(uint8_t, in.bsz);
>  
> -    for (out_pos = 0; in_pos < size; block_count++) {
> +    for (out_pos = 0; in_pos < size; ) {
>          int in_ret, out_ret;
>  
>          if (in_pos + in.bsz > size) {
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 174aae3..891af14 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -144,15 +144,18 @@ Parameters to dd subcommand:
>  @table @option
>  
>  @item bs=@var{block_size}
> -defines the block size
> +Defines the block size.
>  @item count=@var{blocks}
> -sets the number of input blocks to copy
> +Sets the number of input blocks to copy.
>  @item if=@var{input}
> -sets the input file
> +Sets the input file.
>  @item of=@var{output}
> -sets the output file
> +Sets the output file. dd truncates the output file to zero if 'conv=notrunc'
> +is not specified.
>  @item skip=@var{blocks}
> -sets the number of input blocks to skip
> +Sets the number of input blocks to skip.
> +@item conv=notrunc
> +Makes dd not truncate output file to zero.

Capitalizing other sentences should go as a sepearte patch.

>  @end table
>  
>  Command description:
> @@ -326,7 +329,7 @@ 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 [-f @var{fmt}] [-O @var{output_fmt}] [bs=@var{block_size}] [count=@var{blocks}] [skip=@var{blocks}] [conv=notrunc] 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.
> diff --git a/tests/qemu-iotests/158 b/tests/qemu-iotests/158
> index 5b335db..63e2a10 100755
> --- a/tests/qemu-iotests/158
> +++ b/tests/qemu-iotests/158
> @@ -53,7 +53,7 @@ $QEMU_IO -c "write -P 0xa 0 $size" "$TEST_IMG" | _filter_qemu_io
>  echo
>  echo "== Converting the image with dd =="
>  
> -$QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" -O "$IMGFMT"
> +$QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" conv=notrunc -O "$IMGFMT"
>  TEST_IMG="$TEST_IMG.out" _check_test_img
>  
>  echo
> diff --git a/tests/qemu-iotests/159 b/tests/qemu-iotests/159
> index 825f05f..d68a19f 100755
> --- a/tests/qemu-iotests/159
> +++ b/tests/qemu-iotests/159
> @@ -55,7 +55,8 @@ for bs in $TEST_SIZES; do
>      echo
>      echo "== Converting the image with dd with a block size of $bs =="
>  
> -    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" bs=$bs -O "$IMGFMT"
> +    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" bs=$bs conv=notrunc \
> +        -O "$IMGFMT"
>      TEST_IMG="$TEST_IMG.out" _check_test_img
>  
>      echo
> diff --git a/tests/qemu-iotests/160 b/tests/qemu-iotests/160
> index 5c910e5..53b3c30 100755
> --- a/tests/qemu-iotests/160
> +++ b/tests/qemu-iotests/160
> @@ -55,10 +55,11 @@ for skip in $TEST_SKIP_BLOCKS; do
>      echo
>      echo "== Converting the image with dd with skip=$skip =="
>  
> -    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" skip="$skip" -O "$IMGFMT" \
> -        2> /dev/null
> +    $QEMU_IMG dd if="$TEST_IMG" of="$TEST_IMG.out" skip="$skip" conv=notrunc  \
> +        -O "$IMGFMT" 2> /dev/null
>      TEST_IMG="$TEST_IMG.out" _check_test_img
> -    dd if="$TEST_IMG" of="$TEST_IMG.out.dd" skip="$skip" status=none
> +    dd if="$TEST_IMG" of="$TEST_IMG.out.dd" skip="$skip" conv=notrunc \
> +        status=none
>  
>      echo
>      echo "== Compare the images with qemu-img compare =="
> -- 
> 2.9.2
> 

Apart from above, the conv=notrunc code looks good to me. Thanks!

Fam