From: Pádraig Brady Date: Thu, 31 Mar 2011 10:28:58 +0000 (+0100) Subject: copy: link rather than copy symlinks, when --link used X-Git-Tag: v8.11~29 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=594292a1d89332dd006cd7fe3116cf46ebe9acf6;p=thirdparty%2Fcoreutils.git copy: link rather than copy symlinks, when --link used This bug was introduced in commit ca9e212c, 2009-09-24, "cp, mv: use linkat to guarantee semantics", which inadvertently disabled the creation of hardlinks to symlinks. However rather than implementing the intention of that commit and relying on gnulib linkat emulation, we'll revert to the previous emulation as that maintains ownership and timestamps. * src/copy.c (copy_internal): Use our existing hardlink to symlink emulation when link() might dereference the symlink. Also ensure that we copy the timestamps of the original symlink when we use the emulation. * tests/cp/link-symlink: Add a test to ensure timestamps copied. * tests/Makefile.am: Reference the new test. * NEWS: Mention the fix. Reported by Ruediger Meier --- diff --git a/NEWS b/NEWS index 6d66355c3c..9af1cd9c15 100644 --- a/NEWS +++ b/NEWS @@ -4,6 +4,10 @@ GNU coreutils NEWS -*- outline -*- ** Bug fixes + cp -a --link would not create a hardlink to a symlink, instead + copying the symlink and then not preserving its timestamp. + [bug introduced in coreutils-8.0] + cut could segfault when invoked with a user-specified output delimiter and an unbounded range like "-f1234567890-". [bug introduced in coreutils-5.3.0] diff --git a/src/copy.c b/src/copy.c index 104652d063..e839f973f6 100644 --- a/src/copy.c +++ b/src/copy.c @@ -2169,13 +2169,24 @@ copy_internal (char const *src_name, char const *dst_name, } } - /* cp, invoked with `--link --no-dereference', should not follow the - link; we guarantee this with gnulib's linkat module (on systems - where link(2) follows the link, gnulib creates a symlink with - identical contents, which is good enough for our purposes). */ + /* POSIX 2008 states that it is implementation-defined whether + link() on a symlink creates a hard-link to the symlink, or only + to the referent (effectively dereferencing the symlink) (POSIX + 2001 required the latter behavior, although many systems provided + the former). Yet cp, invoked with `--link --no-dereference', + should not follow the link. We can approximate the desired + behavior by skipping this hard-link creating block and instead + copying the symlink, via the `S_ISLNK'- copying code below. + LINK_FOLLOWS_SYMLINKS is tri-state; if it is -1, we don't know + how link() behaves, so we use the fallback case for safety. + + Note gnulib's linkat module, guarantees that the symlink is not + dereferenced. However its emulation currently doesn't maintain + timestamps or ownership so we only call it when we know the + emulation will not be needed. */ else if (x->hard_link - && (!S_ISLNK (src_mode) - || x->dereference != DEREF_NEVER)) + && !(LINK_FOLLOWS_SYMLINKS && S_ISLNK (src_mode) + && x->dereference == DEREF_NEVER)) { if (linkat (AT_FDCWD, src_name, AT_FDCWD, dst_name, 0)) { @@ -2298,7 +2309,9 @@ copy_internal (char const *src_name, char const *dst_name, /* If we've just created a hard-link due to cp's --link option, we're done. */ - if (x->hard_link && ! S_ISDIR (src_mode)) + if (x->hard_link && ! S_ISDIR (src_mode) + && !(LINK_FOLLOWS_SYMLINKS && S_ISLNK (src_mode) + && x->dereference == DEREF_NEVER)) return delayed_ok; if (copied_as_regular) diff --git a/tests/Makefile.am b/tests/Makefile.am index 99b46e8e86..e7f3fffb12 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -328,6 +328,7 @@ TESTS = \ cp/link \ cp/link-no-deref \ cp/link-preserve \ + cp/link-symlink \ cp/no-deref-link1 \ cp/no-deref-link2 \ cp/no-deref-link3 \ diff --git a/tests/cp/link-symlink b/tests/cp/link-symlink new file mode 100755 index 0000000000..443b337db5 --- /dev/null +++ b/tests/cp/link-symlink @@ -0,0 +1,41 @@ +#!/bin/sh +# Ensure that cp -a --link maintains timestamps if possible + +# Copyright (C) 2011 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 . + +. "${srcdir=.}/init.sh"; path_prepend_ ../src +print_ver_ cp + +# Check that the timestamps of the symlink are copied +# if we're using hardlink to symlink emulation. +touch file +ln -s file link || framework_failure +touch -m -h -d 2011-01-01 link || + skip_test_ "Your system doesn't support updating symlink timestamps" +case `stat --format=%y link` in + 2011-01-01*) ;; + *) skip_test_ "Your system doesn't support updating symlink timestamps" ;; +esac + +# link.cp is probably a hardlink, but may also be a symlink +# In either case the timestamp should match the original. +cp -al link link.cp +case `stat --format=%y link.cp` in + 2011-01-01*) ;; + *) fail=1 ;; +esac + +Exit $fail