xfs: create scaffolding for creating debugfs entries

Set up debugfs directories for xfs as a whole, and a subdirectory for
each mounted filesystem.  This will enable the creation of debugfs files
in the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/xfs_linux.h

@@ -63,6 +63,7 @@ typedef __u32			xfs_nlink_t;
 #include <linux/rhashtable.h>
 #include <linux/xattr.h>
 #include <linux/mnt_idmapping.h>
+#include <linux/debugfs.h>
 
 #include <asm/page.h>
 #include <asm/div64.h>

fs/xfs/xfs_mount.h

@@ -208,6 +208,7 @@ typedef struct xfs_mount {
 	uint64_t		m_resblks_avail;/* available reserved blocks */
 	uint64_t		m_resblks_save;	/* reserved blks @ remount,ro */
 	struct delayed_work	m_reclaim_work;	/* background inode reclaim */
+	struct dentry		*m_debugfs;	/* debugfs parent */
 	struct xfs_kobj		m_kobj;
 	struct xfs_kobj		m_error_kobj;
 	struct xfs_kobj		m_error_meta_kobj;

fs/xfs/xfs_super.c

@@ -49,6 +49,7 @@
 
 static const struct super_operations xfs_super_operations;
 
+static struct dentry *xfs_debugfs;	/* top-level xfs debugfs dir */
 static struct kset *xfs_kset;		/* top-level xfs sysfs dir */
 #ifdef DEBUG
 static struct xfs_kobj xfs_dbg_kobj;	/* global debug sysfs attrs */
@@ -758,6 +759,7 @@ static void
 xfs_mount_free(
 	struct xfs_mount	*mp)
 {
+	debugfs_remove(mp->m_debugfs);
 	kfree(mp->m_rtname);
 	kfree(mp->m_logname);
 	kmem_free(mp);
@@ -1479,6 +1481,21 @@ xfs_fs_validate_params(
 	return 0;
 }
 
+struct dentry *
+xfs_debugfs_mkdir(
+	const char	*name,
+	struct dentry	*parent)
+{
+	struct dentry	*child;
+
+	/* Apparently we're expected to ignore error returns?? */
+	child = debugfs_create_dir(name, parent);
+	if (IS_ERR(child))
+		return NULL;
+
+	return child;
+}
+
 static int
 xfs_fs_fill_super(
 	struct super_block	*sb,
@@ -1521,6 +1538,13 @@ xfs_fs_fill_super(
 	if (error)
 		goto out_free_names;
 
+	if (xfs_debugfs) {
+		mp->m_debugfs = xfs_debugfs_mkdir(mp->m_super->s_id,
+						  xfs_debugfs);
+	} else {
+		mp->m_debugfs = NULL;
+	}
+
 	error = xfs_init_mount_workqueues(mp);
 	if (error)
 		goto out_close_devices;
@@ -2353,10 +2377,12 @@ init_xfs_fs(void)
 	if (error)
 		goto out_cleanup_procfs;
 
+	xfs_debugfs = xfs_debugfs_mkdir("xfs", NULL);
+
 	xfs_kset = kset_create_and_add("xfs", NULL, fs_kobj);
 	if (!xfs_kset) {
 		error = -ENOMEM;
-		goto out_sysctl_unregister;
+		goto out_debugfs_unregister;
 	}
 
 	xfsstats.xs_kobj.kobject.kset = xfs_kset;
@@ -2400,7 +2426,8 @@ init_xfs_fs(void)
 	free_percpu(xfsstats.xs_stats);
  out_kset_unregister:
 	kset_unregister(xfs_kset);
- out_sysctl_unregister:
+ out_debugfs_unregister:
+	debugfs_remove(xfs_debugfs);
 	xfs_sysctl_unregister();
  out_cleanup_procfs:
 	xfs_cleanup_procfs();
@@ -2427,6 +2454,7 @@ exit_xfs_fs(void)
 	xfs_sysfs_del(&xfsstats.xs_kobj);
 	free_percpu(xfsstats.xs_stats);
 	kset_unregister(xfs_kset);
+	debugfs_remove(xfs_debugfs);
 	xfs_sysctl_unregister();
 	xfs_cleanup_procfs();
 	xfs_mru_cache_uninit();

fs/xfs/xfs_super.h

@@ -100,4 +100,6 @@ extern struct workqueue_struct *xfs_discard_wq;
 
 #define XFS_M(sb)		((struct xfs_mount *)((sb)->s_fs_info))
 
+struct dentry *xfs_debugfs_mkdir(const char *name, struct dentry *parent);
+
 #endif	/* __XFS_SUPER_H__ */