Fix statechange-led.sh & unnecessary libdevmapper warning

- Fix autoreplace behaviour on statechange-led.sh script.

ZED sends the following events on an auto-replace:

1. statechange: Disk goes UNAVAIL->ONLINE
2. statechange: Disk goes ONLINE->UNAVAIL
3. vdev_attach: Disk goes ONLINE

Events 1-2 happen when ZED first attempts to do an auto-online.  When that
fails, ZED then tries an auto-replace, generating the vdev_attach event in #3.

In the previous code, statechange-led was only looking at the UNAVAIL->ONLINE
transition to turn off the LED.  It ignored the #2 ONLINE->UNAVAIL transition,
assuming it was just the "old" VDEV going offline.  This is problematic, as
a drive can go from ONLINE->UNAVAIL when it's malfunctioning, and we don't want
to ignore that.

This new patch correctly turns on the fault LED every time a drive becomes
UNAVAIL.  It also monitors vdev_attach events to trigger turning off the LED
when an auto-replaced disk comes online.

- Remove unnecessary libdevmapper warning with --with-config=kernel

This fixes an unnecessary libdevmapper warning when building
--with-config=kernel.  Kernel code does not use libdevmapper, so the warning
is not needed.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tony Hutter <[email protected]>
Closes #2375 
Closes #5312 
Closes #5331 

1 files changed, 3 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index e9f50f783..39bd54c17 100644
--- a/configure.ac
+++ b/configure.ac
@@ -304,6 +304,7 @@ AC_CONFIG_FILES([
 
 AC_OUTPUT
 
-AS_IF([test "x$user_libdevmapper" != xyes ], [
-    AC_MSG_WARN([Building without libdevmapper.  Auto-replace, auto-online, and statechange-led.sh may not work correctly with device mapper vdevs.])
+AS_IF([test "x$user_libdevmapper" != xyes && test "$ZFS_CONFIG" != kernel ], [
+    AC_MSG_WARN([Building without libdevmapper.  Auto-replace, auto-online, \
+and statechange-led.sh may not work correctly with device mapper vdevs.])
 ])