kdump: add udev events for memory online/offline

Currently no udev events for memory hotplug "online" and "offline" are
generated:

  # udevadm monitor
  # echo offline > /sys/devices/system/memory/memory4/state
  ==> No event

When kdump is loaded, kexec detects the current memory configuration and
stores it in the pre-allocated ELF core header.  Therefore, for kdump it
is necessary to reload the kdump kernel with kexec when the memory
configuration changes (e.g.  for online/offline hotplug memory).

In order to do this automatically, udev rules should be used.  This kernel
patch adds udev events for "online" and "offline".  Together with this
kernel patch, the following udev rules for online/offline have to be added
to "/etc/udev/rules.d/98-kexec.rules":

  SUBSYSTEM=="memory", ACTION=="online", PROGRAM="/etc/init.d/kdump restart"
  SUBSYSTEM=="memory", ACTION=="offline", PROGRAM="/etc/init.d/kdump restart"

[[email protected]: fixups for class to subsystem conversion]
Signed-off-by: Michael Holzheu <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Kay Sievers <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Greg KH <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index f17e3ea041c0..ed5de58c340f 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -295,11 +295,22 @@ static int memory_block_change_state(struct memory_block *mem,
 
 	ret = memory_block_action(mem->start_section_nr, to_state);
 
-	if (ret)
+	if (ret) {
 		mem->state = from_state_req;
-	else
-		mem->state = to_state;
+		goto out;
+	}
 
+	mem->state = to_state;
+	switch (mem->state) {
+	case MEM_OFFLINE:
+		kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
+		break;
+	case MEM_ONLINE:
+		kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
+		break;
+	default:
+		break;
+	}
 out:
 	mutex_unlock(&mem->state_mutex);
 	return ret;