Subject: cp: --sparse=always loses tail-end sparseness
Package: coreutils
Version: 5.2.1-2
Severity: minor
Tags: patch
cp --sparse=always fails to maximize sparseness when a file ends with a
partial block cotaining only zeros:
$ dd if=/dev/null of=sparse bs=32769 seek=1 count=0
0+0 records in
0+0 records out
0 bytes transferred in 0.001514 seconds (0 bytes/sec)
$ ls -ls sparse
0 -rw------- 1 pacman users 32769 Jun 6 13:45 sparse
$ cp --sparse=always sparse sparse2
$ ls -ls sparse2
4 -rw------- 1 pacman users 32769 Jun 6 13:46 sparse2
$
This is caused by an unnecessary write() before the ftruncate() which sets
the file size.
--- src/copy.c.orig 2006-06-06 13:58:23.000000000 -0500
+++ src/copy.c 2006-06-06 14:32:58.000000000 -0500
@@ -363,16 +363,15 @@
}
}
- /* 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' and ftruncate is not available,
+ something needs to be written at the end. 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)
+ /* ftruncate sets the file size, so there is no need for a write. */
+ if (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
-- System Information:
Debian Release: 3.1
Architecture: powerpc (ppc)
Kernel: Linux 2.6.16.14
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Versions of packages coreutils depends on:
ii libacl1 2.2.23-1 Access control list shared library
ii libc6 2.3.2.ds1-22sarge3 GNU C Library: Shared libraries an
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