On 01/22/2013 02:53 PM, Ondrej Oprala wrote:
The patch is based on this entry
https://bugzilla.redhat.com/show_bug.cgi?id=502026 . It delays
allocation if possible (as suggested in
http://lists.gnu.org/archive/html/bug-coreutils/2009-05/msg00223.html ),
skipping it altogether if dd is not being used for actual copying.
Hi Ondrej,
thanks for working on this.
* src/dd.c (dd_copy): Move and split the code for buffer
allocations to separate functions and call them conditionally.
(alloc_ibuf): Allocate memory for the input buffer.
(alloc_obuf): Allocate memory for the output buffer.
Please describe what you did to alloc_ibuf + sibling:
you added the function, so please tell so, e.g. something like
* src/dd.c (alloc_ibuf, alloc_obuf): Add new function with code
factored out from ...
(dd_copy): ... here. Call the above new functions to allocate
memory for ibuf and obuf at the beginning if needed, or later.
And please add also the new definition of ibuf as a global,
static variable.
diff --git a/src/dd.c b/src/dd.c
[...]
+ /* Delay buffer allocation if possible*/
s/\(possible\)/\1. /
diff --git a/tests/dd/no-allocate.sh b/tests/dd/no-allocate.sh
[...]
+#count and skip is zero, we don't need to allocate memory for input block
+(ulimit -v 10000;dd if=/dev/zero of=x bs=10M count=0) || fail=1
+#non-skippable input, we need to allocate input block size (and we should fail)
+(ulimit -v 10000; echo "abcde" | dd of=x bs=10M seek=1 skip=1 count=0) &&
fail=1
s/#/# /
require_ulimit_
Other than that, the patch looks quite okay - although I needed some time
to find out if there could be a situation where ibuf is not yet allocated
and alloc_obuf lets obuf point to ibuf, but obuf is yet used before ibuf
is allocated later ... and I'm still not 100% convinced.
Can someone confirm this?
(At least, this corner case is not obvious by reading.)
Have a nice day,
Berny
DIFF