On 02/02/11 13:23, Pádraig Brady wrote:
> This looks like another candidate to auto enable fullblock for.
> https://bugzilla.redhat.com/show_bug.cgi?id=614605
> I.E. oflag=direct
Attached is a proposed solution to this.
I'm worried about the last condition though
where we enable 'fullblock' when both count and bs are specified.
For example this would still work:
# Output first 2 parts
$ (echo part1; sleep 1; echo part2; sleep 1; echo discard) |
dd count=2 obs=1 2>/dev/null
part1
part2
However this would not:
# Output first 2 parts, each being up to 4096 bytes
$ (echo part1; sleep 1; echo part2; sleep 1; echo discard) |
dd count=2 ibs=4096 obs=1 2>/dev/null
part1
part2
discard
So how contrived is the last example,
given how brittle such a construct is?
cheers,
Pádraig.
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index ea35afe..9167537 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -8089,7 +8089,7 @@ Do not truncate the output file.
@opindex sync @r{(padding with @acronym{ASCII} @sc{nul}s)}
Pad every input block to size of @samp{ibs} with trailing zero bytes.
When used with @samp{block} or @samp{unblock}, pad with spaces instead of
-zero bytes.
+zero bytes. This implies the @samp{fullblock} flag.
@item fdatasync
@opindex fdatasync
@@ -8135,8 +8135,8 @@ output file to be truncated before being appended to.
@cindex concurrent I/O
Use concurrent I/O mode for data. This mode performs direct I/O
and drops the @acronym{POSIX} requirement to serialize all I/O to the same file.
-A file cannot be opened in CIO mode and with a standard open at the
-same time.
+A file cannot be opened in CIO mode and with a standard open at the same time.
+This implies the @samp{fullblock} flag.
@item direct
@opindex direct
@@ -8146,6 +8146,7 @@ Note that the kernel may impose restrictions on read or write buffer sizes.
For example, with an ext4 destination file system and a linux-based kernel,
using @samp{oflag=direct} will cause writes to fail with @code{EINVAL} if the
output buffer size is not a multiple of 512.
+This implies the @samp{fullblock} flag.
@item directory
@opindex directory
diff --git a/src/dd.c b/src/dd.c
index daddc1e..5b56970 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -1075,6 +1075,19 @@ scanargs (int argc, char *const *argv)
conversions_mask |= C_TWOBUFS;
}
+ /* Enable 'fullblock' as one wouldn't want random
+ padding applied, when reading from a pipe for example. */
+ if (conversions_mask & C_SYNC)
+ input_flags |= O_FULLBLOCK;
+ /* Enable 'fullblock' with 'direct' or 'cio' as again if reading from
+ a pipe, we're constrained in how we write to output. */
+ else if ((input_flags | output_flags) & (O_DIRECT | O_CIO))
+ input_flags |= O_FULLBLOCK;
+ /* Enable 'fullblock' if we're reading a specific number of blocks,
+ with a specific block size. */
+ else if (max_records && max_records != (uintmax_t) -1 && input_blocksize)
+ input_flags |= O_FULLBLOCK;
+
if (input_blocksize == 0)
input_blocksize = DEFAULT_BLOCKSIZE;
if (output_blocksize == 0)
