[PATCH] dd: add 'fullblock' iflag.
Nicholas Clark
nicholas.clark at gmail.com
Thu Jan 25 18:11:30 UTC 2018
Looks great! Do you think we should include a different way to tell the
user that some of their requested data didn't actually get written?
On Thu, Jan 25, 2018 at 11:01 AM, Denys Vlasenko <vda.linux at googlemail.com>
wrote:
> Applied without the code which prints warning.
> Please try current git.
>
> On Wed, Jan 24, 2018 at 7:05 PM, Nicholas Clark
> <nicholas.clark at gmail.com> 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 <nicholas.clark at gmail.com>
> > ---
> > 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
> >
> > _______________________________________________
> > busybox mailing list
> > busybox at busybox.net
> > http://lists.busybox.net/mailman/listinfo/busybox
>
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