xfs: add xfs_mount sysfs kobject

Embed a base kobject into xfs_mount. This creates a kobject associated
with each XFS mount and a subdirectory in sysfs with the name of the
filesystem. The subdirectory lifecycle matches that of the mount. Also
add the new xfs_sysfs.[c,h] source files with some XFS sysfs
infrastructure to facilitate attribute creation.

Note that there are currently no attributes exported as part of the
xfs_mount kobject. It exists solely to serve as a per-mount container
for child objects.

Signed-off-by: Brian Foster <[e-mail]>
Reviewed-by: Dave Chinner <[e-mail]>
Signed-off-by: Dave Chinner <[e-mail]>

fs/xfs/Makefile

···
 				   xfs_mru_cache.o \
 				   xfs_super.o \
 				   xfs_symlink.o \
+				   xfs_sysfs.o \
 				   xfs_trans.o \
 				   xfs_xattr.o \
 				   kmem.o \

fs/xfs/xfs_linux.h

···
 #define MAX(a,b)	(max(a,b))
 #define howmany(x, y)	(((x)+((y)-1))/(y))
 
+/*
+ * XFS wrapper structure for sysfs support. It depends on external data
+ * structures and is embedded in various internal data structures to implement
+ * the XFS sysfs object heirarchy. Define it here for broad access throughout
+ * the codebase.
+ */
+struct xfs_kobj {
+	struct kobject		kobject;
+	struct completion	complete;
+};
+
 /* Kernel uid/gid conversion. These are used to convert to/from the on disk
  * uid_t/gid_t types to the kuid_t/kgid_t types that the kernel uses internally.
  * The conversion here is type only, the value will remain the same since we

fs/xfs/xfs_mount.c

···
 #include "xfs_trace.h"
 #include "xfs_icache.h"
 #include "xfs_dinode.h"
+#include "xfs_sysfs.h"
 
 
 #ifdef HAVE_PERCPU_SB
···
 static DEFINE_MUTEX(xfs_uuid_table_mutex);
 static int xfs_uuid_table_size;
 static uuid_t *xfs_uuid_table;
+
+extern struct kset *xfs_kset;
 
 /*
  * See if the UUID is unique among mounted XFS filesystems.
···
 
 	xfs_set_maxicount(mp);
 
-	error = xfs_uuid_mount(mp);
+	mp->m_kobj.kobject.kset = xfs_kset;
+	error = xfs_sysfs_init(&mp->m_kobj, &xfs_mp_ktype, NULL, mp->m_fsname);
 	if (error)
 		goto out;
+
+	error = xfs_uuid_mount(mp);
+	if (error)
+		goto out_remove_sysfs;
 
 	/*
 	 * Set the minimum read and write sizes
···
 	xfs_da_unmount(mp);
  out_remove_uuid:
 	xfs_uuid_unmount(mp);
+ out_remove_sysfs:
+	xfs_sysfs_del(&mp->m_kobj);
  out:
 	return error;
 }
···
 	xfs_errortag_clearall(mp, 0);
 #endif
 	xfs_free_perag(mp);
+
+	xfs_sysfs_del(&mp->m_kobj);
 }
 
 int

fs/xfs/xfs_mount.h

···
 						   on the next remount,rw */
 	int64_t			m_low_space[XFS_LOWSP_MAX];
 						/* low free space thresholds */
+	struct xfs_kobj		m_kobj;
 
 	struct workqueue_struct	*m_data_workqueue;
 	struct workqueue_struct	*m_unwritten_workqueue;

fs/xfs/xfs_sysfs.c

···
+/*
+ * Copyright (c) 2014 Red Hat, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include "xfs.h"
+#include "xfs_sysfs.h"
+
+struct xfs_sysfs_attr {
+	struct attribute attr;
+	ssize_t (*show)(char *buf, void *data);
+	ssize_t (*store)(const char *buf, size_t count, void *data);
+};
+
+static inline struct xfs_sysfs_attr *
+to_attr(struct attribute *attr)
+{
+	return container_of(attr, struct xfs_sysfs_attr, attr);
+}
+
+#define XFS_SYSFS_ATTR_RW(name) \
+	static struct xfs_sysfs_attr xfs_sysfs_attr_##name = __ATTR_RW(name)
+#define XFS_SYSFS_ATTR_RO(name) \
+	static struct xfs_sysfs_attr xfs_sysfs_attr_##name = __ATTR_RO(name)
+
+#define ATTR_LIST(name) &xfs_sysfs_attr_##name.attr
+
+/*
+ * xfs_mount kobject. This currently has no attributes and thus no need for show
+ * and store helpers. The mp kobject serves as the per-mount parent object that
+ * is identified by the fsname under sysfs.
+ */
+
+struct kobj_type xfs_mp_ktype = {
+	.release = xfs_sysfs_release,
+};

fs/xfs/xfs_sysfs.h

···
+/*
+ * Copyright (c) 2014 Red Hat, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef __XFS_SYSFS_H__
+#define __XFS_SYSFS_H__
+
+extern struct kobj_type xfs_mp_ktype;	/* xfs_mount */
+
+static inline struct xfs_kobj *
+to_kobj(struct kobject *kobject)
+{
+	return container_of(kobject, struct xfs_kobj, kobject);
+}
+
+static inline void
+xfs_sysfs_release(struct kobject *kobject)
+{
+	struct xfs_kobj *kobj = to_kobj(kobject);
+	complete(&kobj->complete);
+}
+
+static inline int
+xfs_sysfs_init(
+	struct xfs_kobj		*kobj,
+	struct kobj_type	*ktype,
+	struct xfs_kobj		*parent_kobj,
+	const char		*name)
+{
+	init_completion(&kobj->complete);
+	return kobject_init_and_add(&kobj->kobject, ktype,
+				    &parent_kobj->kobject, "%s", name);
+}
+
+static inline void
+xfs_sysfs_del(
+	struct xfs_kobj	*kobj)
+{
+	kobject_del(&kobj->kobject);
+	kobject_put(&kobj->kobject);
+	wait_for_completion(&kobj->complete);
+}
+
+#endif	/* __XFS_SYSFS_H__ */