Honor dd's noatime flag if possible, even if not supported on build fs

* doc/coreutils.texi (dd invocation): Warn that noatime might not be
reliable.
* src/dd.c (flags, usage): Look at O_NOATIME, not
HAVE_WORKING_O_NOATIME, to decide whether to support the noatime
flag, so that dd attempts O_NOATIME even if the build file system
does not support it.  Problem reported by Jim Meyering today in
bug-coreutils.
* tests/dd/misc: Generate a warning, not a failure, if noatime
exists but fails.

diff --git a/ChangeLog b/ChangeLog
index fabf1a3..938ffb2 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,19 @@
        This avoids a harmless (but distracting) case of memory being
        used-uninitialized.
 
+2007-02-21  Paul Eggert  <eggert@cs.ucla.edu>
+
+       Honor dd's noatime flag if possible, even if not supported on build fs
+       * doc/coreutils.texi (dd invocation): Warn that noatime might not be
+       reliable.
+       * src/dd.c (flags, usage): Look at O_NOATIME, not
+       HAVE_WORKING_O_NOATIME, to decide whether to support the noatime
+       flag, so that dd attempts O_NOATIME even if the build file system
+       does not support it.  Problem reported by Jim Meyering today in
+       bug-coreutils.
+       * tests/dd/misc: Generate a warning, not a failure, if noatime
+       exists but fails.
+
 2007-02-21  Jim Meyering  <jim@meyering.net>
 
        * tests/misc/date: Remove vestigial use of Data::Dumper.

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 1a2dba4..04c1b4e 100644 (file)
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7442,6 +7442,8 @@ Use non-blocking I/O.
 @opindex noatime
 @cindex access time
 Do not update the file's access time.
+Some older file systems silently ignore this flag, so it is a good
+idea to test it on your files before relying on it.
 
 @item noctty
 @opindex noctty

diff --git a/src/dd.c b/src/dd.c
index d699955..27a4a08 100644 (file)
--- a/src/dd.c
+++ b/src/dd.c
@@ -265,7 +265,7 @@ static struct symbol_value const flags[] =
   {"direct",   O_DIRECT},
   {"directory",        O_DIRECTORY},
   {"dsync",    O_DSYNC},
-  {"noatime",  HAVE_WORKING_O_NOATIME ? O_NOATIME : 0},
+  {"noatime",  O_NOATIME},
   {"noctty",   O_NOCTTY},
   {"nofollow", HAVE_WORKING_O_NOFOLLOW ? O_NOFOLLOW : 0},
   {"nolinks",  O_NOLINKS},
@@ -472,7 +472,7 @@ Each FLAG symbol may be:\n\
        fputs (_("  sync      likewise, but also for metadata\n"), stdout);
       if (O_NONBLOCK)
        fputs (_("  nonblock  use non-blocking I/O\n"), stdout);
-      if (HAVE_WORKING_O_NOATIME)
+      if (O_NOATIME)
        fputs (_("  noatime   do not update access time\n"), stdout);
       if (O_NOCTTY)
        fputs (_("  noctty    do not assign controlling terminal from file\n"),

diff --git a/tests/dd/misc b/tests/dd/misc
index 513221b..fa5cfbe 100755 (executable)
--- a/tests/dd/misc
+++ b/tests/dd/misc
@@ -29,6 +29,8 @@ if test "$VERBOSE" = yes; then
   dd --version
 fi
 
+fail=0
+warn=0
 test_failure=0
 echo data > $tmp_in || test_failure=1
 ln $tmp_in $tmp_in2 || test_failure=1
@@ -63,8 +65,15 @@ sleep 1
 if dd iflag=noatime if=$tmp_in of=$tmp_out 2> /dev/null; then
   new_ls=`ls -u --full-time $tmp_in`
   if test "x$old_ls" != "x$new_ls"; then
-    echo "dd iflag=noatime updated atime; O_NOATIME bug in your kernel?" >&2
-    fail=1
+    cat >&2 <<EOF
+=================================================================
+$0: WARNING!!!
+This operating system has the O_NOATIME file status flag,
+but it is silently ignored in some cases.
+Therefore, dd options like iflag=noatime may be silently ignored.
+=================================================================
+EOF
+    warn=77
   fi
 fi
 
@@ -77,6 +86,7 @@ fi
 outbytes=`echo x | dd bs=3 ibs=10 obs=10 conv=sync 2>/dev/null | wc -c`
 test "$outbytes" -eq 3 || fail=1
 
-rm -f $tmp_in $tmp_in2 $tmp_sym $tmp_out
+rm -f $tmp_in $tmp_in2 $tmp_sym $tmp_out || fail=1
 
+test $fail -eq 0 && fail=$warn
 exit $fail