ocfs2: add dlm_recover_callback_support in sysfs

This is a part of the nocontrold feature which was incorporated sometime
back.

This is required for backward compatibility of the tools, specifically
the scenario where the tools with recovery callback is used with a
kernel not using the recovery callbacks (older kernel + newer tools).
The tools look for this file to understand if the kernel supports DLM
recovery callbacks.

For kernels which support recovery callbacks but will miss this patch,
ocfs2 will continue to use the older API and would still be able to
mount the filesystem.

[[email protected]: simplify]
[[email protected]: VERIFY_OCTAL_PERMISSIONS fix up]
Signed-off-by: Goldwyn Rodrigues <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[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, 0 deletions

diff --git a/fs/ocfs2/stackglue.c b/fs/ocfs2/stackglue.c
index ca5ce14cbddc..5c8343fe7438 100644
--- a/fs/ocfs2/stackglue.c
+++ b/fs/ocfs2/stackglue.c
@@ -603,11 +603,25 @@ static struct kobj_attribute ocfs2_attr_cluster_stack =
 	       ocfs2_cluster_stack_show,
 	       ocfs2_cluster_stack_store);
 
+
+
+static ssize_t ocfs2_dlm_recover_show(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "1\n");
+}
+
+static struct kobj_attribute ocfs2_attr_dlm_recover_support =
+	__ATTR(dlm_recover_callback_support, S_IRUGO,
+	       ocfs2_dlm_recover_show, NULL);
+
 static struct attribute *ocfs2_attrs[] = {
 	&ocfs2_attr_max_locking_protocol.attr,
 	&ocfs2_attr_loaded_cluster_plugins.attr,
 	&ocfs2_attr_active_cluster_plugin.attr,
 	&ocfs2_attr_cluster_stack.attr,
+	&ocfs2_attr_dlm_recover_support.attr,
 	NULL,
 };