Applied without the code which prints warning.
Please try current git.

On Wed, Jan 24, 2018 at 7:05 PM, Nicholas Clark
<[email protected]> wrote:
> Adds a fullblock iflag for improved compatibility with GNU dd.
> The new iflag can be used to ensure that dd calls retrieve the
> expected amount of data when reading from pipes or unusual
> filesystems.
>
> Signed-off-by: Nicholas Clark <[email protected]>
> ---
>  coreutils/dd.c             | 64 
> +++++++++++++++++++++++++++++++++++++++-------
>  docs/posix_conformance.txt |  5 ++--
>  2 files changed, 58 insertions(+), 11 deletions(-)
>
> diff --git a/coreutils/dd.c b/coreutils/dd.c
> index d302f35d3..760420687 100644
> --- a/coreutils/dd.c
> +++ b/coreutils/dd.c
> @@ -37,7 +37,7 @@
>  //config:      elapsed time and speed.
>  //config:
>  //config:config FEATURE_DD_IBS_OBS
> -//config:      bool "Enable ibs, obs and conv options"
> +//config:      bool "Enable ibs, obs, iflag and conv options"
>  //config:      default y
>  //config:      depends on DD
>  //config:      help
> @@ -57,7 +57,7 @@
>
>  //usage:#define dd_trivial_usage
>  //usage:       "[if=FILE] [of=FILE] " IF_FEATURE_DD_IBS_OBS("[ibs=N] [obs=N] 
> ") "[bs=N] [count=N] [skip=N]\n"
> -//usage:       "       [seek=N]" IF_FEATURE_DD_IBS_OBS(" 
> [conv=notrunc|noerror|sync|fsync] [iflag=skip_bytes]")
> +//usage:       "       [seek=N]" IF_FEATURE_DD_IBS_OBS(" 
> [conv=notrunc|noerror|sync|fsync] [iflag=skip_bytes|fullblock]")
>  //usage:#define dd_full_usage "\n\n"
>  //usage:       "Copy a file with converting and formatting\n"
>  //usage:     "\n       if=FILE         Read from FILE instead of stdin"
> @@ -79,6 +79,7 @@
>  //usage:     "\n       conv=fsync      Physically write data out before 
> finishing"
>  //usage:     "\n       conv=swab       Swap every pair of bytes"
>  //usage:     "\n       iflag=skip_bytes        skip=N is in bytes"
> +//usage:     "\n       iflag=fullblock Try to read full blocks from input"
>  //usage:       )
>  //usage:       IF_FEATURE_DD_STATUS(
>  //usage:     "\n       status=noxfer   Suppress rate output"
> @@ -110,6 +111,10 @@ struct globals {
>         unsigned long long begin_time_us;
>  #endif
>         int flags;
> +#if ENABLE_FEATURE_DD_IBS_OBS
> +       char warn_en;
> +       char previous_partial;
> +#endif
>  } FIX_ALIASING;
>  #define G (*(struct globals*)bb_common_bufsiz1)
>  #define INIT_G() do { \
> @@ -130,11 +135,13 @@ enum {
>         /* start of input flags */
>         FLAG_IFLAG_SHIFT = 5,
>         FLAG_SKIP_BYTES = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
> +       FLAG_FULLBLOCK = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
>         /* end of input flags */
> -       FLAG_TWOBUFS = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
> -       FLAG_COUNT   = 1 << 7,
> -       FLAG_STATUS_NONE = 1 << 8,
> -       FLAG_STATUS_NOXFER = 1 << 9,
> +       FLAG_TWOBUFS = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
> +       FLAG_COUNT   = 1 << 8,
> +       FLAG_BS   = 1 << 9,
> +       FLAG_STATUS_NONE = 1 << 10,
> +       FLAG_STATUS_NOXFER = 1 << 11,
>  };
>
>  static void dd_output_status(int UNUSED_PARAM cur_signal)
> @@ -189,6 +196,25 @@ static ssize_t full_write_or_warn(const void *buf, 
> size_t len,
>         return n;
>  }
>
> +#if ENABLE_FEATURE_DD_IBS_OBS
> +static ssize_t read_and_warn(int fd, void *buf, size_t count)
> +{
> +       ssize_t result = safe_read(fd, buf, count);
> +
> +       if (result <= 0) {
> +               return result;
> +       }
> +
> +       if (G.previous_partial && G.warn_en) {
> +               G.warn_en = 0;
> +               bb_error_msg("warn: partial read; suggest iflag=fullblock");
> +       }
> +
> +       G.previous_partial = (result < count);
> +       return result;
> +}
> +#endif
> +
>  static bool write_and_stats(const void *buf, size_t len, size_t obs,
>         const char *filename)
>  {
> @@ -251,7 +277,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>         static const char conv_words[] ALIGN1 =
>                 "notrunc\0""sync\0""noerror\0""fsync\0""swab\0";
>         static const char iflag_words[] ALIGN1 =
> -               "skip_bytes\0";
> +               "skip_bytes\0""fullblock\0";
>  #endif
>  #if ENABLE_FEATURE_DD_STATUS
>         static const char status_words[] ALIGN1 =
> @@ -290,6 +316,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>         /* Partially implemented: */
>         //swab          swap every pair of input bytes: will abort on 
> non-even reads
>                 OP_iflag_skip_bytes,
> +               OP_iflag_fullblock,
>  #endif
>         };
>         smallint exitcode = EXIT_FAILURE;
> @@ -347,6 +374,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>                 if (what == OP_ibs) {
>                         /* Must fit into positive ssize_t */
>                         ibs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, 
> cwbkMG_suffixes);
> +                       G.flags |= FLAG_BS;
>                         /*continue;*/
>                 }
>                 if (what == OP_obs) {
> @@ -365,6 +393,9 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>                 if (what == OP_bs) {
>                         ibs = xatoul_range_sfx(val, 1, ((size_t)-1L)/2, 
> cwbkMG_suffixes);
>                         obs = ibs;
> +#if ENABLE_FEATURE_DD_IBS_OBS
> +                       G.flags |= FLAG_BS;
> +#endif
>                         /*continue;*/
>                 }
>                 /* These can be large: */
> @@ -405,6 +436,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>         ibuf = xmalloc(ibs);
>         obuf = ibuf;
>  #if ENABLE_FEATURE_DD_IBS_OBS
> +       G.warn_en = (G.flags & (FLAG_BS + FLAG_COUNT)) == (FLAG_BS + 
> FLAG_COUNT);
>         if (ibs != obs) {
>                 G.flags |= FLAG_TWOBUFS;
>                 obuf = xmalloc(obs);
> @@ -450,7 +482,15 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>                 size_t blocksz = (G.flags & FLAG_SKIP_BYTES) ? 1 : ibs;
>                 if (lseek(ifd, skip * blocksz, SEEK_CUR) < 0) {
>                         do {
> -                               ssize_t n = safe_read(ifd, ibuf, blocksz);
> +                               ssize_t n;
> +#if ENABLE_FEATURE_DD_IBS_OBS
> +                               if (G.flags & FLAG_FULLBLOCK)
> +                                       n = full_read(ifd, ibuf, blocksz);
> +                               else
> +                                       n = read_and_warn(ifd, ibuf, blocksz);
> +#else
> +                               n = safe_read(ifd, ibuf, blocksz);
> +#endif
>                                 if (n < 0)
>                                         goto die_infile;
>                                 if (n == 0)
> @@ -465,8 +505,14 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
>
>         while (!(G.flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
>                 ssize_t n;
> -
> +#if ENABLE_FEATURE_DD_IBS_OBS
> +               if (G.flags & FLAG_FULLBLOCK)
> +                       n = full_read(ifd, ibuf, ibs);
> +               else
> +                       n = read_and_warn(ifd, ibuf, ibs);
> +#else
>                 n = safe_read(ifd, ibuf, ibs);
> +#endif
>                 if (n == 0)
>                         break;
>                 if (n < 0) {
> diff --git a/docs/posix_conformance.txt b/docs/posix_conformance.txt
> index 8b9112020..cdf89b744 100644
> --- a/docs/posix_conformance.txt
> +++ b/docs/posix_conformance.txt
> @@ -178,9 +178,10 @@ dd POSIX options:
>    conv=noerror    |  yes   |           |
>    conv=notrunc    |  yes   |           |
>    conv=sync       |  yes   |           |
> +dd compatibility options:
> +  conv=fsync      |  yes   |           |
>    iflag=skip_bytes|  yes   |           |
> -dd Busybox specific options:
> - conv=fsync
> +  iflag=fullblock |  yes   |           |
>
>  df POSIX options
>   option           | exists | compliant | remarks
> --
> 2.14.1
>
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