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cp: make --attributes-only override --reflink completely

* doc/coreutils.texi (cp invocation): Change the description slightly
so as users might not immediately discount using this option.
Mention that --reflink is overridden by the other linking options and
--attributes-only, and give an example where this might be useful.
* src/copy.c (copy_internal): Bypass the reflink if
--attributes-only is specifed.
* tests/cp/reflink-perm: Ensure both --reflink modes are
overridden by --attributes-only.
* NEWS: Mention the change in behavior.
Reported by Jim Meyering.
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1 parent 0d792d0 commit 883ac22239036025896ff99bd4b2a6d02712f39f @pixelb pixelb committed Oct 26, 2010
Showing with 23 additions and 6 deletions.
  1. +5 −0 NEWS
  2. +13 −5 doc/coreutils.texi
  3. +2 −1 src/copy.c
  4. +3 −0 tests/cp/reflink-perm
@@ -7,6 +7,11 @@ GNU coreutils NEWS -*- outline -*-
tail -F once again notices changes in a currently unavailable
remote directory [bug introduced in coreutils-7.5]
+** Changes in behavior
+ cp --attributes-only now completely overrides --reflink.
+ Previously a reflink was needlessly attempted.
* Noteworthy changes in release 8.6 (2010-10-15) [stable]
@@ -7614,12 +7614,11 @@ implementations that dereference symbolic links by default.
@cindex COW
@cindex clone
@cindex copy on write
-Perform a lightweight, copy-on-write (COW) copy.
-Copying with this option can succeed only on some file systems.
-Once it has succeeded, beware that the source and destination files
-share the same disk data blocks as long as they remain unmodified.
+Perform a lightweight, copy-on-write (COW) copy, if supported by the
+file system. Once it has succeeded, beware that the source and destination
+files share the same disk data blocks as long as they remain unmodified.
Thus, if a disk I/O error affects data blocks of one of the files,
-the other suffers the exact same fate.
+the other suffers the same fate.
The @var{when} value can be one of the following:
@@ -7633,6 +7632,15 @@ If the copy-on-write operation is not supported then fall back
to the standard copy behaviour.
@end table
+This option is overridden by the @option{--link}, @option{--symbolic-link}
+and @option{--attributes-only} options, thus allowing it to be used
+to configure the default data copying behavior for @command{cp}.
+For example, with the following alias, @command{cp} will use the
+minimum amount of space supported by the file system.
+alias cp='cp --reflink=auto --sparse=always'
+@end example
@item --remove-destination
@opindex --remove-destination
@@ -622,7 +622,8 @@ copy_reg (char const *src_name, char const *dst_name,
goto close_src_and_dst_desc;
- if (x->reflink_mode)
+ /* --attributes-only overrides --reflink. */
+ if (data_copy_required && x->reflink_mode)
bool clone_ok = clone_file (dest_desc, source_desc) == 0;
if (clone_ok || x->reflink_mode == REFLINK_ALWAYS)
@@ -39,8 +39,11 @@ test "$mode" = "-rwxrwxrwx" || fail=1
test copy -nt file && fail=1
+# Ensure that --attributes-only overrides --reflink completely
echo > file2 # file with data
cp --reflink=auto --preserve --attributes-only file2 empty_copy || fail=1
test -s empty_copy && fail=1
+cp --reflink=always --preserve --attributes-only file2 empty_copy || fail=1
+test -s empty_copy && fail=1
Exit $fail

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