* NEWS: Fix cp --sparse so that it preserves tail-end sparseness, even

when the file's apparent size is not a multiple of its block size.
* src/copy.c (copy_reg): Don't write a NUL before calling ftruncate.
For some file sizes, writing that single byte would unnecessarily
waste a few file blocks.  That write may have been necessary in the
early days of Linux, but now, removing it should be safe.
Based on a patch by Alan Curry: <http://bugs.debian.org/370792>
* tests/cp/sparse: New test for the above.
* tests/cp/Makefile.am (TESTS): Add sparse.

* tests/sparse-file: New file, essence factored out of...
* tests/du/8gb: ... here.  Use the new script.

7 files changed, 124 insertions, 26 deletions

diff --git a/ChangeLog b/ChangeLog
index bbfb3a78f..04ae75989 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2006-08-19  Jim Meyering  <jim@meyering.net>
+
+	* NEWS: Fix cp --sparse so that it preserves tail-end sparseness, even
+	when the file's apparent size is not a multiple of its block size.
+	* src/copy.c (copy_reg): Don't write a NUL before calling ftruncate.
+	For some file sizes, writing that single byte would unnecessarily
+	waste a few file blocks.  That write may have been necessary in the
+	early days of Linux, but now, removing it should be safe.
+	Based on a patch by Alan Curry: <http://bugs.debian.org/370792>
+	* tests/cp/sparse: New test for the above.
+	* tests/cp/Makefile.am (TESTS): Add sparse.
+
+	* tests/sparse-file: New file, essence factored out of...
+	* tests/du/8gb: ... here.  Use the new script.
+
 2006-08-18  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* src/system.h (select_plural): Reduce by 1000000, not 1000, since
diff --git a/NEWS b/NEWS
index 6882f75d6..6eeb49492 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,10 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  cp --sparse preserves sparseness at the end of a file, even when
+  the file's apparent size is not a multiple of its block size.
+  [introduced with the original design, in fileutils-4.0r, 2000-04-29]
+
   df (with a command line argument) once again prints its header
   [introduced in coreutils-6.0]
 
diff --git a/src/copy.c b/src/copy.c
index 0a3f9e504..e11dd77f8 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -461,21 +461,21 @@ copy_reg (char const *src_name, char const *dst_name,
 	    }
 	}
 
-      /* If the file ends with a `hole', something needs to be written at
-	 the end.  Otherwise the kernel would truncate the file at the end
-	 of the last write operation.  */
+      /* If the file ends with a `hole', we need to do something to record
+	 the length of the file.  On modern systems, calling ftruncate does
+	 the job.  On systems without native ftruncate support, we have to
+	 write a byte at the ending position.  Otherwise the kernel would
+	 truncate the file at the end of the last write operation.  */
 
       if (last_write_made_hole)
 	{
-#if HAVE_FTRUNCATE
-	  /* Write a null character and truncate it again.  */
-	  if (full_write (dest_desc, "", 1) != 1
-	      || ftruncate (dest_desc, n_read_total) < 0)
-#else
-	  /* Seek backwards one character and write a null.  */
-	  if (lseek (dest_desc, (off_t) -1, SEEK_CUR) < 0L
-	      || full_write (dest_desc, "", 1) != 1)
-#endif
+	  if (HAVE_FTRUNCATE
+	      ? /* ftruncate sets the file size,
+		   so there is no need for a write.  */
+	      ftruncate (dest_desc, n_read_total) < 0
+	      : /* Seek backwards one character and write a null.  */
+	      (lseek (dest_desc, (off_t) -1, SEEK_CUR) < 0L
+	       || full_write (dest_desc, "", 1) != 1))
 	    {
 	      error (0, errno, _("writing %s"), quote (dst_name));
 	      return_val = false;
diff --git a/tests/cp/Makefile.am b/tests/cp/Makefile.am
index 1a4aa84f4..5b4c23606 100644
--- a/tests/cp/Makefile.am
+++ b/tests/cp/Makefile.am
@@ -21,6 +21,7 @@
 AUTOMAKE_OPTIONS = 1.1 gnits
 
 TESTS = \
+  sparse \
   link-no-deref \
   cp-deref \
   acl \
diff --git a/tests/cp/sparse b/tests/cp/sparse
new file mode 100755
index 000000000..2842513b0
--- /dev/null
+++ b/tests/cp/sparse
@@ -0,0 +1,57 @@
+#!/bin/sh
+# Test cp --sparse=always
+
+# Copyright (C) 2006 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 2 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, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  cp --version
+fi
+
+. $srcdir/../envvar-check
+. $srcdir/../sparse-file
+
+pwd=`pwd`
+t0=`echo "$0"|sed 's,.*/,,'`.tmp; tmp=$t0/$$
+trap 'status=$?; cd $pwd; chmod -R u+rwx $t0; rm -rf $t0 && exit $status' 0
+trap '(exit $?); exit $?' 1 2 13 15
+
+framework_failure=0
+mkdir -p $tmp || framework_failure=1
+cd $tmp || framework_failure=1
+
+# Create a sparse file.
+# It has to be at least 128K in order to be sparse on some systems.
+# Make its size one larger than 128K, in order to tickle the
+# bug in coreutils-6.0.
+size=`expr 128 \* 1024 + 1`
+dd bs=1 seek=$size of=sparse < /dev/null 2> /dev/null || framework_failure=1
+
+if test $framework_failure = 1; then
+  echo "$0: failure in testing framework" 1>&2
+  (exit 1); exit 1
+fi
+
+fail=0
+
+cp --sparse=always sparse copy || fail=1
+
+# Ensure that the copy has the same block count as the original.
+test `stat --printf %b sparse` = `stat --printf %b copy` || fail=1
+
+(exit $fail); exit $fail
diff --git a/tests/du/8gb b/tests/du/8gb
index 036cb8699..0e7cfcdef 100755
--- a/tests/du/8gb
+++ b/tests/du/8gb
@@ -2,7 +2,7 @@
 # Ensure that du does not rely on narrow types like size_t for
 # file sizes or sums.
 
-# Copyright (C) 2003, 2005 Free Software Foundation, Inc.
+# Copyright (C) 2003, 2005, 2006 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
@@ -25,6 +25,7 @@ if test "$VERBOSE" = yes; then
 fi
 
 . $srcdir/../envvar-check
+. $srcdir/../sparse-file
 
 pwd=`pwd`
 t0=`echo "$0"|sed 's,.*/,,'`.tmp; tmp=$t0/$$
@@ -40,19 +41,6 @@ if test $framework_failure = 1; then
   (exit 1); exit 1
 fi
 
-# If this file system doesn't support sparse files,
-# don't try to create a file that'd end up consuming 8GB.
-# This happens on Darwin6.5 with a file system of type `hfs'.
-# NTFS requires 128K before a hole appears in a sparse file.
-dd bs=1 seek=128K of=t < /dev/null 2> /dev/null
-set x `du -sk t`
-if test "$2" -ge 128; then
-  echo "$0: skipping this test, since this file system doesn't support" 1>&2
-  echo "$0: sparse files and this test requires a file with an apparent" 1>&2
-  echo "$0: size of 8GB" 1>&2
-  (exit 77); exit 77
-fi
-
 dd bs=1 seek=8G of=big < /dev/null 2> /dev/null
 if test $? != 0; then
   echo "$0: cannot create a file large enough for this test; possibly" 1>&2
diff --git a/tests/sparse-file b/tests/sparse-file
new file mode 100644
index 000000000..4d8c7a6bd
--- /dev/null
+++ b/tests/sparse-file
@@ -0,0 +1,33 @@
+# -*- sh -*-
+# Does the current (working-dir.) file system support sparse files?
+
+# Copyright (C) 2006 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 2 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, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+# Test whether we can create a sparse file.
+# For example, on Darwin6.5 with a file system of type hfs, it's not possible.
+# NTFS requires 128K before a hole appears in a sparse file.
+t=sparse.$$
+dd bs=1 seek=128K of=$t < /dev/null 2> /dev/null
+set x `du -sk $t`
+kb_size=$2
+rm -f $t
+if test $kb_size -ge 128; then
+  echo "$0: skipping this test, since this file system doesn't support" \
+    sparse files 1>&2
+  (exit 77); exit 77
+fi