Enhancement patch for autofs v4.1.4 init.d script

["Gordon Lack" <gml4410@ggr.co.uk>]

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   The init.d autofs script runs a check for "maps within maps"
(actually mountpoints within mountpoints) which it does by looping over
all knownmaps and grepping for a start-of-line match in both directions
(ie: 2 greps).

   I was testing some things on a system with 39 maps and was surprised
to find the autofs script took 38 seconds to report on required
reloads.  Testing showed that there were ~3000 runs of grep called by
this piece of code.

   It is possible to do the same test with internal case statements. 
This removes ~3000 calls to grep (I have another system with 49 map, so
it gets nearly 5000...).  With this fix applied the autofs script ran in
one quarter of the time.

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--- autofs-4.1.4/samples/rc.autofs.in	2006-08-22 14:48:51.000000000 +0100
+++ autofs.enhance	2006-08-22 14:49:51.000000000 +0100
@@ -233,11 +233,21 @@
 	    # another map or another map, maps on top of it.
 	    for knownmap in $knownmaps
 	    do	
-		if [ "`echo $dir/ | grep ^$knownmap`" != "" \
-			-o "`echo $knownmap | grep ^$dir/`" != "" \]
-		then 
-		    continue 2
-		fi
+# This gets run for all maps on all maps, so is O(n^2)
+# This means 3500 external grep calls for 38 map entries,
+# which is slow.  case statements make it much faster.
+#
+#		if [ "`echo $dir/ | grep ^$knownmap`" != "" \
+#			-o "`echo $knownmap | grep ^$dir/`" != "" \]
+#		then 
+#		    continue 2
+#		fi
+                case "$dir/" in
+                $knownmap*)   continue 2 ;;
+                esac
+                case "$knownmap" in
+                $dir/*)   continue 2 ;;
+                esac
 	    done
 
 	    if [ ! -z "$dir" -a ! -z "$map" \

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