cp: use far less memory in some cases

cp --link was "remembering" many name,dev,inode triples unnecessarily.
cp was doing the same, even without --link, for every directory in the
source hierarchy, while it can do its job with entries merely for the
command-line arguments.  Prompted by a report from Patrick Shoenfeld.
Details <http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/15081>.
* src/copy.c (copy_internal): Refrain from remembering
name,dev,inode for most files, when invoked via cp --link.
Record an infloop-avoidance triple for each directory specified
on the command line, not for each directory in the source tree.
Don't record a dir-triple when x->hard_link is set.
* NEWS (Buf fixes): Mention it.
* tests/cp/link-heap: New file.  Test for cp's lowered memory usage.
* tests/Makefile.am (TESTS): Add link-heap.

NEWS

@@ -10,6 +10,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  cp uses much less memory in some situations
+
   seq 9223372036854775807 9223372036854775808 now prints only two numbers
   on systems with extended long double support and good library support.
   Even with this patch, on some systems, it still produces invalid output,

src/copy.c

@@ -1411,6 +1411,10 @@ copy_internal (char const *src_name, char const *dst_name,
      we can arrange to create a hard link between the corresponding names
      in the destination tree.
 
+     When using the --link (-l) option, there is no need to take special
+     measures, because (barring race conditions) files that are hard-linked
+     in the source tree will also be hard-linked in the destination tree.
+
      Sometimes, when preserving links, we have to record dev/ino even
      though st_nlink == 1:
      - when in move_mode, since we may be moving a group of N hard-linked
@@ -1429,27 +1433,29 @@ copy_internal (char const *src_name, char const *dst_name,
      - likewise for -L except that it applies to all files, not just
 	command line arguments.
 
-     Also record directory dev/ino when using --recursive.  We'll use that
-     info to detect this problem: cp -R dir dir.  FIXME-maybe: ideally,
-     directory info would be recorded in a separate hash table, since
-     such entries are useful only while a single command line hierarchy
-     is being copied -- so that separate table could be cleared between
-     command line args.  Using the same hash table to preserve hard
-     links means that it may not be cleared.  */
+     Also, with --recursive, record dev/ino of each command-line directory.
+     We'll use that info to detect this problem: cp -R dir dir.  */
 
   if (x->move_mode && src_sb.st_nlink == 1)
     {
       earlier_file = src_to_dest_lookup (src_sb.st_ino, src_sb.st_dev);
     }
-  else if ((x->preserve_links
-	    && (1 < src_sb.st_nlink
-		|| (command_line_arg
-		    && x->dereference == DEREF_COMMAND_LINE_ARGUMENTS)
-		|| x->dereference == DEREF_ALWAYS))
-	   || (x->recursive && S_ISDIR (src_mode)))
+  else if (x->preserve_links
+	   && !x->hard_link
+	   && (1 < src_sb.st_nlink
+	       || (command_line_arg
+		   && x->dereference == DEREF_COMMAND_LINE_ARGUMENTS)
+	       || x->dereference == DEREF_ALWAYS))
     {
       earlier_file = remember_copied (dst_name, src_sb.st_ino, src_sb.st_dev);
     }
+  else if (x->recursive && S_ISDIR (src_mode))
+    {
+      if (command_line_arg)
+	earlier_file = remember_copied (dst_name, src_sb.st_ino, src_sb.st_dev);
+      else
+	earlier_file = src_to_dest_lookup (src_sb.st_ino, src_sb.st_dev);
+    }
 
   /* Did we copy this inode somewhere else (in this command line argument)
      and therefore this is a second hard link to the inode?  */
@@ -1730,8 +1736,8 @@ copy_internal (char const *src_name, char const *dst_name,
 	  /* Insert the created directory's inode and device
              numbers into the search structure, so that we can
              avoid copying it again.  */
-
-	  remember_copied (dst_name, dst_sb.st_ino, dst_sb.st_dev);
+	  if (!x->hard_link)
+	    remember_copied (dst_name, dst_sb.st_ino, dst_sb.st_dev);
 
 	  if (x->verbose)
 	    emit_verbose (src_name, dst_name, NULL);

tests/Makefile.am

@@ -262,6 +262,7 @@ TESTS =						\
   cp/file-perm-race				\
   cp/into-self					\
   cp/link					\
+  cp/link-heap					\
   cp/link-no-deref				\
   cp/link-preserve				\
   cp/no-deref-link1				\

tests/cp/link-heap

@@ -0,0 +1,41 @@
+#!/bin/sh
+# ensure that cp --preserve=link --link doesn't waste heap
+
+# Copyright (C) 2008 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 <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  cp --version
+fi
+
+. $srcdir/test-lib.sh
+expensive_
+require_ulimit_
+
+a=$(printf %031d 0)
+b=$(printf %031d 1)
+(mkdir $a \
+   && cd $a \
+   && seq --format=%031g 10000 |xargs touch \
+   && seq --format=d%030g 10000 |xargs mkdir ) || framework_failure
+cp -al $a $b || framework_failure
+mkdir e || framework_failure
+mv $a $b e || framework_failure
+
+fail=0
+(ulimit -v 10000; cp -al e f) || fail=1
+
+Exit $fail