s390/zcore: release dump save area on restart or power down

The zFCP/NVMe standalone dumper is supposed to release the dump save area
resource as soon as possible but might fail to do so, for instance, if it
crashes. To avoid this situation, register a reboot notifier and ensure
the dump save area resource is released on reboot or power down.
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/char/zcore.c

@@ -15,6 +15,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/debugfs.h>
+#include <linux/reboot.h>
 
 #include <asm/asm-offsets.h>
 #include <asm/ipl.h>
@@ -238,6 +239,28 @@ static int __init zcore_reipl_init(void)
 	return 0;
 }
 
+static int zcore_reboot_and_on_panic_handler(struct notifier_block *self,
+					     unsigned long	   event,
+					     void		   *data)
+{
+	if (hsa_available)
+		release_hsa();
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block zcore_reboot_notifier = {
+	.notifier_call	= zcore_reboot_and_on_panic_handler,
+	/* we need to be notified before reipl and kdump */
+	.priority	= INT_MAX,
+};
+
+static struct notifier_block zcore_on_panic_notifier = {
+	.notifier_call	= zcore_reboot_and_on_panic_handler,
+	/* we need to be notified before reipl and kdump */
+	.priority	= INT_MAX,
+};
+
 static int __init zcore_init(void)
 {
 	unsigned char arch;
@@ -298,6 +321,9 @@ static int __init zcore_init(void)
 	zcore_hsa_file = debugfs_create_file("hsa", S_IRUSR|S_IWUSR, zcore_dir,
 					     NULL, &zcore_hsa_fops);
 
+	register_reboot_notifier(&zcore_reboot_notifier);
+	atomic_notifier_chain_register(&panic_notifier_list, &zcore_on_panic_notifier);
+
 	return 0;
 fail:
 	diag308(DIAG308_REL_HSA, NULL);