Re: bug with ls: unnecessary stat calls on symlink targets

[Jim Meyering]

Jim Meyering <address@hidden> wrote:
> I'll check in something like the following once I've written a test.
...

I've done that:

    http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=0a744370bb9a5


 ChangeLog                   |   16 +++++++++
 THANKS                      |    1 +
 src/ls.c                    |    8 ++++-
 tests/Makefile.am           |    1 +
 tests/ls/Makefile.am        |    1 +
 tests/ls/stat-free-symlinks |   72 +++++++++++++++++++++++++++++++++++++++++++
 tests/mv/atomic             |   15 +--------
 tests/strace                |   30 ++++++++++++++++++
 8 files changed, 130 insertions(+), 14 deletions(-)
 create mode 100755 tests/ls/stat-free-symlinks
 create mode 100644 tests/strace

diff --git a/ChangeLog b/ChangeLog
index 5da6380..99cbd62 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2007-07-15  Jim Meyering  <address@hidden>
+
+       ls --color: Don't stat symlinks when neither ORPHAN nor MISSING
+       attribute has a color.
+       * src/ls.c (main): Don't set check_symlink_color when C_EXEC is
+       colored, unless ln=target (aka color_symlink_as_referent) is set.
+       (gobble_file): Set f->linkok = true also when !check_symlink_color.
+       http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/10608/focus=10927
+       Reported by Jeremy Maitin-Shepard.
+       * tests/strace: New file, contents extracted from...
+       * tests/mv/atomic: ...here.  Source strace.
+       * tests/ls/stat-free-symlinks: New file.  Test for the above.
+       Use strace to ensure that in this corner case, ls does not call stat.
+       * tests/ls/Makefile.am (TESTS): Add stat-free-symlinks.
+       * tests/Makefile.am (EXTRA_DIST): Add strace.
+
 2007-07-14  Jim Meyering  <address@hidden>

        Remove long-deprecated options.
diff --git a/THANKS b/THANKS
index 7d590b1..601ca8f 100644
--- a/THANKS
+++ b/THANKS
@@ -229,6 +229,7 @@ Jeff Moore                          address@hidden
 Jeff Sheinberg                      address@hidden
 Jens Elkner                         address@hidden
 Jens Schmidt                        address@hidden
+Jeremy Maitin-Shepard               address@hidden
 Jerome Abela                        address@hidden
 Jérôme Zago                         address@hidden
 Jesse Kornblum                      address@hidden
diff --git a/src/ls.c b/src/ls.c
index 751dc3d..204341c 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -1168,7 +1168,7 @@ main (int argc, char **argv)
     {
       /* Avoid following symbolic links when possible.  */
       if (is_colored (C_ORPHAN)
-         || is_colored (C_EXEC)
+         || (is_colored (C_EXEC) && color_symlink_as_referent)
          || (is_colored (C_MISSING) && format == long_format))
        check_symlink_color = true;

@@ -2713,6 +2713,12 @@ gobble_file (char const *name, enum filetype type, ino_t 
inode,
          free (linkname);
        }

+      /* When not distinguishing types of symlinks, pretend we know that
+        it is stat'able, so that it will be colored as a regular symlink,
+        and not as an orphan.  */
+      if (S_ISLNK (f->stat.st_mode) && !check_symlink_color)
+       f->linkok = true;
+
       if (S_ISLNK (f->stat.st_mode))
        f->filetype = symbolic_link;
       else if (S_ISDIR (f->stat.st_mode))
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 682a52c..5606839 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -19,6 +19,7 @@ EXTRA_DIST = \
   expensive group-names input-tty lang-default mk-script \
   other-fs-tmpdir priv-check \
   rwx-to-mode sample-test selinux setgid-check sparse-file \
+  strace \
   umask-check very-expensive

 ## N O T E :: Please do not add new tests/ directories.
diff --git a/tests/ls/Makefile.am b/tests/ls/Makefile.am
index ecd018e..45ca9fe 100644
--- a/tests/ls/Makefile.am
+++ b/tests/ls/Makefile.am
@@ -18,6 +18,7 @@
 # 02110-1301, USA.

 TESTS = \
+  stat-free-symlinks \
   nameless-uid \
   color-dtype-dir \
   stat-failed \
diff --git a/tests/ls/stat-free-symlinks b/tests/ls/stat-free-symlinks
new file mode 100755
index 0000000..78d91c9
--- /dev/null
+++ b/tests/ls/stat-free-symlinks
@@ -0,0 +1,72 @@
+#!/bin/sh
+# ensure that ls does not stat a symlink in an unusual case
+
+# Copyright (C) 2007 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, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  ls --version
+fi
+
+. $srcdir/../envvar-check
+. $srcdir/../strace
+
+pwd=`pwd`
+t0=`echo "$0"|sed 's,.*/,,'`.tmp; tmp=$t0/$$
+trap 'status=$?; cd "$pwd" && chmod -R u+rwx $t0 && rm -rf $t0 && exit 
$status' 0
+trap '(exit $?); exit $?' 1 2 13 15
+
+framework_failure=0
+mkdir -p $tmp || framework_failure=1
+cd $tmp || framework_failure=1
+
+touch x || framework_failure=1
+chmod a+x x || framework_failure=1
+ln -s x link-to-x || framework_failure=1
+
+if test $framework_failure = 1; then
+  echo "$0: failure in testing framework" 1>&2
+  (exit 1); exit 1
+fi
+
+fail=0
+
+# ls from coreutils 6.9 would unnecessarily stat a symlink in an unusual case:
+# When not coloring orphan and missing entries, and without ln=target,
+# ensure that ls -F (or -d, or -l: i.e., when not dereferencing)
+# does not stat a symlink to directory, and does still color that
+# symlink and an executable file properly.
+
+LS_COLORS='or=0:mi=0:ex=01;32:ln=01;35' \
+  strace -qe stat ls -F --color=always x link-to-x > out 2> err || fail=1
+
+# With coreutils 6.9 and earlier, this file would contain a
+# line showing ls had called stat on "x".
+test -s err && fail=1
+
+# Check that output is colorized, as requested, too.
+{
+  printf '\e[0m\e[01;address@hidden'
+  printf '\e[01;32mx\e[0m*\n'
+  printf '\e[m'
+} > exp || fail=1
+
+cmp out exp || fail=1
+test $fail = 1 && diff out exp 2> /dev/null
+
+(exit $fail); exit $fail
diff --git a/tests/mv/atomic b/tests/mv/atomic
index 2b49fde..69374b9 100755
--- a/tests/mv/atomic
+++ b/tests/mv/atomic
@@ -23,6 +23,8 @@ if test "$VERBOSE" = yes; then
   mv --version
 fi

+. $srcdir/../strace
+
 pwd=`pwd`
 t0=`echo "$0"|sed 's,.*/,,'`.tmp; tmp=$t0/$$
 trap 'status=$?; cd "$pwd" && chmod -R u+rwx $t0 && rm -rf $t0 && exit 
$status' 0
@@ -48,19 +50,6 @@ if test $framework_failure = 1; then
   (exit 1); exit 1
 fi

-# Skip this test on systems without strace.
-strace -V < /dev/null > ver 2>&1 || skip=1
-if test "$skip" = 1; then
-  echo "$0: no strace program, so skipping this test" 1>&2
-  (exit 77); exit 77
-fi
-
-strace -qe unlink echo > /dev/null 2>&1 || skip=1
-if test "$skip" = 1; then
-  echo "$0: strace doesn't work, so skipping this test" 1>&2
-  (exit 77); exit 77
-fi
-
 fail=0

 strace -qe unlink mv -T s1 s2 > out 2>&1 || fail=1
diff --git a/tests/strace b/tests/strace
new file mode 100644
index 0000000..0bb022a
--- /dev/null
+++ b/tests/strace
@@ -0,0 +1,30 @@
+# Skip the current test if strace is not available or doesn't work.
+
+# Copyright (C) 2007 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, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA.
+
+strace -V < /dev/null > /dev/null 2>&1 ||
+{
+  echo "$0: no strace program, so skipping this test" 1>&2
+  (exit 77); exit 77
+}
+
+strace -qe unlink echo > /dev/null 2>&1 ||
+{
+  echo "$0: strace doesn't work, so skipping this test" 1>&2
+  (exit 77); exit 77
+}
--
1.5.3.rc1.27.ga5e40