dd: work around buffer length restrictions with oflag=direct (O_DIRECT)

dd oflag=direct would fail to copy a file with size that is
not a multiple of 512 (destination file system specific)

* NEWS (Bug fixes): Mention it.
* src/dd.c (iwrite): Turn off O_DIRECT for any
smaller-than-obs-sized write.  Don't bother to restore it.
* tests/dd/direct: New test for the above.
* tests/Makefile.am (TESTS): Add dd/direct.
* doc/coreutils.texi (dd invocation): Mention oflag=direct
buffer size restriction.
Details in http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/17586
Reported by Eric Sandeen.

1 files changed, 40 insertions, 0 deletions

diff --git a/tests/dd/direct b/tests/dd/direct
new file mode 100755
index 000000000..7e80bee15
--- /dev/null
+++ b/tests/dd/direct
@@ -0,0 +1,40 @@
+#!/bin/sh
+# ensure that dd's oflag=direct works
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  dd --version
+fi
+
+. $srcdir/test-lib.sh
+
+truncate -s 8192 in || framework_failure
+dd if=in oflag=direct of=out 2> /dev/null \
+  || skip_test_ 'this file system lacks support for O_DIRECT'
+
+truncate -s 511 short || framework_failure
+truncate -s 8191 m1 || framework_failure
+truncate -s 8193 p1 || framework_failure
+
+fail=0
+for i in short m1 p1; do
+  rm -f out
+  dd if=$i oflag=direct of=out || fail=1
+done
+
+Exit $fail