=== modified file 'configure.in'
--- configure.in	2009-08-12 09:38:36 +0000
+++ configure.in	2009-08-23 05:23:13 +0000
@@ -419,13 +419,37 @@
   AC_MSG_NOTICE([With pthreads])
 fi
 
-AC_ARG_WITH(aio,
-  AS_HELP_STRING([--with-aio],[Use POSIX AIO]))
-if test "$with_aio" = "yes"; then
-  AC_MSG_NOTICE([With aio])
+with_aio=yes
+NEED_AIO=
+LIBAIO=
+AC_ARG_WITH(aio, AS_HELP_STRING([--without-aio],[Do not use POSIX AIO]))
+dnl Check for POSIX AIO availability
+if test "$with_aio" != "no"; then
+    AC_CHECK_HEADERS(aio.h)
+    dnl On some systems POSIX AIO functions are in librt
+    dnl On some systems POSIX AIO functions are in libaio
+    AC_CHECK_LIB(rt, aio_read,
+      [LIBAIO="-lrt"],
+      AC_CHECK_LIB(aio, aio_read,[LIBAIO="-laio"],
+	AC_MSG_ERROR(POSIX AIO is not available on this system))
+    )
+
+  dnl Enable AIO if the library and headers are found
+  if test "$LIBAIO" != "" && test "$ac_have_aio_h" != ""; then
+    with_aio="yes"
+  else
+    dnl Windows does things differently. We provide wrappers.
+    case "$host_os" in
+      mingw|mingw32)
+        with_aio=yes
+      ;;
+      *)
+        with_aio=no
+      ;;
+    esac
+  fi
 fi
 
-
 AC_ARG_WITH(dl,
   AS_HELP_STRING([--with-dl],[Use dynamic linking]))
 if test "$with_dl" = "yes"; then
@@ -442,6 +466,10 @@
   yes)
 	for dir in $srcdir/src/fs/*; do
 	    module="`basename $dir`"
+	    dnl COSS requires AIO to be auto-enabled.
+	    if test -d "$dir" && test "$module" = "coss" && test "$with_aio" != "yes" ; then
+		continue
+	    fi
 	    if test -d "$dir" && test "$module" != CVS && test "$module" != coss; then
 		STORE_MODULES="$STORE_MODULES $module"
 	    fi
@@ -481,7 +509,6 @@
 NEED_BLOCKING=
 NEED_DISKDAEMON=
 NEED_DISKTHREADS=
-NEED_AIO=
 STORE_TESTS=
 for fs in $STORE_MODULES none; do
     case "$fs" in
@@ -496,6 +523,9 @@
 	NEED_DISKTHREADS="true"
 	;;
     coss)
+	if test "$with_aio" != "yes"; then
+	  AC_MSG_ERROR([COSS requires POSIX AIO which is not available on this system.])
+	fi
 	NEED_AIO="true"
 	dnl
 	dnl Automake om MinGW needs explicit exe extension
@@ -553,6 +583,11 @@
   yes)
 	for dir in $srcdir/src/DiskIO/*; do
 	    module="`basename $dir`"
+	    dnl AIO modules require system support to be auto-enabled.
+	    if test -d "$dir" && test "$module" = "AIO" && test "$with_aio" != "yes" ; then
+		AC_MSG_NOTICE([Autodetected $module DiskIO module but AIO support disabled. Skipping.])
+		continue
+	    fi
 	    if test -d "$dir" && test "$module" != CVS; then
 		AC_MSG_NOTICE([Autodetected $module DiskIO module])
 		DISK_MODULES="$DISK_MODULES $module"
@@ -578,7 +613,10 @@
 if test -n "$DISK_MODULES"; then
     for module in $DISK_MODULES; do
 	if test -d $srcdir/src/DiskIO/$module; then
-	    :
+	  dnl AIO module requires system POSIX AIO support
+	  if test "$module" = "AIO" && test "$with_aio" != "yes"; then
+	    AC_MSG_ERROR(AIO module requires POSIX AIO support which is not available or has been disabled)
+	  fi
 	else
 	    AC_MSG_ERROR(disk-io $module does not exist)
 	fi
@@ -599,11 +637,11 @@
     DiskThreads)
 	FOUND_DISKTHREADS="true"
 	;;
-    AIO)
-    	FOUND_AIO="true"
-	;;
     Blocking)
 	FOUND_BLOCKING="true"
+	;;
+    *)
+      ;;
     esac
 done
 
@@ -629,15 +667,29 @@
     DISK_LINKOBJS="$DISK_LINKOBJS DiskIO/DiskThreads/DiskThreadsDiskIOModule.o"
 fi
 
-if test -z "$FOUND_AIO" && test -n "$NEED_AIO"; then
-    AC_MSG_NOTICE([adding AIO, as it is used by an active, legacy Store Module])
-    DISK_LIBS="$DISK_LIBS libAIO.a"
-    DISK_MODULES="$DISK_MODULES AIO"
-    DISK_LINKOBJS="$DISK_LINKOBJS DiskIO/AIO/AIODiskIOModule.o"
+dnl Use the POSIX AIO pieces if we actually need them.
+if test "$with_aio" = "yes" && test "$NEED_AIO" = "true" ; then
+  AC_MSG_NOTICE([adding AIO, as it is used by an active, legacy Store Module])
+  DISK_LIBS="$DISK_LIBS $LIBAIO libAIO.a"
+  DISK_MODULES="$DISK_MODULES AIO"
+  DISK_LINKOBJS="$DISK_LINKOBJS DiskIO/AIO/AIODiskIOModule.o"
+  case "$host_os" in
+    mingw|mingw32)
+      USE_AIO_WIN32=1
+      AC_MSG_NOTICE([Aio IO Module used, Windows overlapped I/O support automatically enabled])
+      ;;
+    *)
+      AC_MSG_NOTICE([Aio IO Module used, aio support automatically enabled])
+      ;;
+  esac
+else
+  if test "$NEED_AIO" = "true" ; then
+    AC_MSG_NOTICE([AIO support is not needed. Automatically disabled.])
+  fi
 fi
+
 AC_MSG_NOTICE([IO Modules built: $DISK_MODULES])
 USE_AIOPS_WIN32=0
-USE_AIO_WIN32=0
 dnl we know what is being built. now add dependencies.
 for fs in $DISK_MODULES none; do
     case "$fs" in
@@ -655,32 +707,9 @@
             esac
 	fi
 	;;
-    AIO)
-	if test -z "$with_aio"; then
-            case "$host_os" in
-            mingw|mingw32)
-        	USE_AIO_WIN32=1
-	        AC_MSG_NOTICE([Aio IO Module used, Windows overlapped I/O support automatically enabled])
-                ;;
-            *)
-	        AC_MSG_NOTICE([Aio IO Module used, aio support automatically enabled])
-	        with_aio=yes
-                ;;
-            esac
-	fi
-	;;
     esac
 done
 
-dnl Check for librt
-dnl We use AIO in the coss store
-if test "$with_aio" = "yes"; then
-    dnl On some systems POSIX AIO functions are in libaio
-    AC_CHECK_LIB(rt, aio_read,
-      [DISK_LIBS="$DISK_LIBS -lrt"],
-      AC_CHECK_LIB(aio, aio_read,[DISK_LIBS="$DISK_LIBS -laio"])
-    )
-fi
 
 dnl Check for pthreads
 dnl We use pthreads when doing ASYNC I/O
@@ -2080,7 +2109,6 @@
 AC_HEADER_STDC
 
 AC_CHECK_HEADERS( \
-	aio.h \
 	arpa/inet.h \
 	arpa/nameser.h \
 	assert.h \