Actually I remember now why we didn't want --reflink mutually exclusive with other options. It's so it can be used as configuration to change the data copy method employed. I.E. it operates on much the same level as --sparse in that the results are mostly transparent to the user. I.E. cp could be aliased like this to minimize the amount of space that cp uses:
alias cp='cp --reflink=auto --sparse=always' So therefore I've changed the patch as per the attached. I'll apply in a few hours. cheers, Pádraig.
>From 3dc499ba27b1b0b6365179cb6d7bc9e5f6456600 Mon Sep 17 00:00:00 2001 From: =?utf-8?q?P=C3=A1draig=20Brady?= <[email protected]> Date: Tue, 26 Oct 2010 17:55:10 +0100 Subject: [PATCH] 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. --- NEWS | 5 +++++ doc/coreutils.texi | 18 +++++++++++++----- src/copy.c | 3 ++- tests/cp/reflink-perm | 3 +++ 4 files changed, 23 insertions(+), 6 deletions(-) diff --git a/NEWS b/NEWS index 7dbbf1f..dcb9745 100644 --- a/NEWS +++ b/NEWS @@ -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] diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 4d17ed1..0b5a3d3 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -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. + +...@example +alias cp='cp --reflink=auto --sparse=always' +...@end example @item --remove-destination @opindex --remove-destination diff --git a/src/copy.c b/src/copy.c index df31592..07501df 100644 --- a/src/copy.c +++ b/src/copy.c @@ -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) diff --git a/tests/cp/reflink-perm b/tests/cp/reflink-perm index 77f119f..e1c12aa 100755 --- a/tests/cp/reflink-perm +++ b/tests/cp/reflink-perm @@ -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 -- 1.6.2.5
