[PATCH 14/18] powernv/opalcore: provide an option to invalidate /proc/opalcore file

[Hari Bathini <hbathini@linux.ibm.com>]

Writing '1' to /sys/kernel/fadump_release_opalcore would release the
memory held by kernel in exporting /proc/opalcore file.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/platforms/powernv/opal-core.c |   39 ++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/opal-core.c b/arch/powerpc/platforms/powernv/opal-core.c
index 5355d95..f9473b7 100644
--- a/arch/powerpc/platforms/powernv/opal-core.c
+++ b/arch/powerpc/platforms/powernv/opal-core.c
@@ -19,6 +19,8 @@
 #include <linux/proc_fs.h>
 #include <linux/elf.h>
 #include <linux/elfcore.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
 #include <linux/slab.h>
 #include <linux/crash_core.h>
 #include <linux/of.h>
@@ -532,6 +534,36 @@ static void opalcore_cleanup(void)
 }
 __exitcall(opalcore_cleanup);
 
+static ssize_t fadump_release_opalcore_store(struct kobject *kobj,
+					     struct kobj_attribute *attr,
+					     const char *buf, size_t count)
+{
+	int input = -1;
+
+	if (kstrtoint(buf, 0, &input))
+		return -EINVAL;
+
+	if (input == 1) {
+		if (oc_conf == NULL) {
+			pr_err("'/proc/opalcore' file does not exist!\n");
+			return -EPERM;
+		}
+
+		/*
+		 * Take away '/proc/opalcore' and release all memory
+		 * used for exporting this file.
+		 */
+		opalcore_cleanup();
+	} else
+		return -EINVAL;
+
+	return count;
+}
+
+static struct kobj_attribute opalcore_rel_attr = __ATTR(fadump_release_opalcore,
+						0200, NULL,
+						fadump_release_opalcore_store);
+
 /* Init function for opalcore module. */
 static int __init opalcore_init(void)
 {
@@ -558,6 +590,13 @@ static int __init opalcore_init(void)
 					     &proc_opalcore_operations);
 	if (oc_conf->proc_opalcore)
 		proc_set_size(oc_conf->proc_opalcore, oc_conf->opalcore_size);
+
+	rc = sysfs_create_file(kernel_kobj, &opalcore_rel_attr.attr);
+	if (rc) {
+		pr_warn("unable to create sysfs file fadump_release_opalcore (%d)\n",
+			rc);
+	}
+
 	return 0;
 }
 fs_initcall(opalcore_init);