nilfs2: add /sys/fs/nilfs2/<device>/checkpoints group

This patch adds creation of /sys/fs/nilfs2/<device>/checkpoints
group.

The checkpoints group contains attributes that describe
details about volume's checkpoints:
(1) checkpoints_number - show number of checkpoints on volume.
(2) snapshots_number - show number of snapshots on volume.
(3) last_seg_checkpoint - show checkpoint number of the latest segment.
(4) next_checkpoint - show next checkpoint number.
Signed-off-by: NVyacheslav Dubeyko <Vyacheslav.Dubeyko@hgst.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/ABI/testing/sysfs-fs-nilfs2

@@ -210,3 +210,34 @@ Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
 Description:
 		Describe attributes of /sys/fs/nilfs2/<device>/segments
 		group.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/checkpoints_number
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of checkpoints on volume.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/snapshots_number
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show number of snapshots on volume.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/last_seg_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show checkpoint number of the latest segment.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/next_checkpoint
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Show next checkpoint number.
+
+What:		/sys/fs/nilfs2/<device>/checkpoints/README
+Date:		April 2014
+Contact:	"Vyacheslav Dubeyko" <slava@dubeyko.com>
+Description:
+		Describe attributes of /sys/fs/nilfs2/<device>/checkpoints
+		group.

fs/nilfs2/sysfs.c

@@ -111,6 +111,119 @@ void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
 	kobject_del(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
 }
 
+/************************************************************************
+ *                      NILFS checkpoints attrs                         *
+ ************************************************************************/
+
+static ssize_t
+nilfs_checkpoints_checkpoints_number_show(struct nilfs_checkpoints_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	__u64 ncheckpoints;
+	struct nilfs_cpstat cpstat;
+	int err;
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_cpfile_get_stat(nilfs->ns_cpfile, &cpstat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (err < 0) {
+		printk(KERN_ERR "NILFS: unable to get checkpoint stat: err=%d\n",
+			err);
+		return err;
+	}
+
+	ncheckpoints = cpstat.cs_ncps;
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n", ncheckpoints);
+}
+
+static ssize_t
+nilfs_checkpoints_snapshots_number_show(struct nilfs_checkpoints_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 nsnapshots;
+	struct nilfs_cpstat cpstat;
+	int err;
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_cpfile_get_stat(nilfs->ns_cpfile, &cpstat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (err < 0) {
+		printk(KERN_ERR "NILFS: unable to get checkpoint stat: err=%d\n",
+			err);
+		return err;
+	}
+
+	nsnapshots = cpstat.cs_nsss;
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n", nsnapshots);
+}
+
+static ssize_t
+nilfs_checkpoints_last_seg_checkpoint_show(struct nilfs_checkpoints_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	__u64 last_cno;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	last_cno = nilfs->ns_last_cno;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n", last_cno);
+}
+
+static ssize_t
+nilfs_checkpoints_next_checkpoint_show(struct nilfs_checkpoints_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 cno;
+
+	down_read(&nilfs->ns_sem);
+	cno = nilfs->ns_cno;
+	up_read(&nilfs->ns_sem);
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n", cno);
+}
+
+static const char checkpoints_readme_str[] =
+	"The checkpoints group contains attributes that describe\n"
+	"details about volume's checkpoints.\n\n"
+	"(1) checkpoints_number\n\tshow number of checkpoints on volume.\n\n"
+	"(2) snapshots_number\n\tshow number of snapshots on volume.\n\n"
+	"(3) last_seg_checkpoint\n"
+	"\tshow checkpoint number of the latest segment.\n\n"
+	"(4) next_checkpoint\n\tshow next checkpoint number.\n\n";
+
+static ssize_t
+nilfs_checkpoints_README_show(struct nilfs_checkpoints_attr *attr,
+				struct the_nilfs *nilfs, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, checkpoints_readme_str);
+}
+
+NILFS_CHECKPOINTS_RO_ATTR(checkpoints_number);
+NILFS_CHECKPOINTS_RO_ATTR(snapshots_number);
+NILFS_CHECKPOINTS_RO_ATTR(last_seg_checkpoint);
+NILFS_CHECKPOINTS_RO_ATTR(next_checkpoint);
+NILFS_CHECKPOINTS_RO_ATTR(README);
+
+static struct attribute *nilfs_checkpoints_attrs[] = {
+	NILFS_CHECKPOINTS_ATTR_LIST(checkpoints_number),
+	NILFS_CHECKPOINTS_ATTR_LIST(snapshots_number),
+	NILFS_CHECKPOINTS_ATTR_LIST(last_seg_checkpoint),
+	NILFS_CHECKPOINTS_ATTR_LIST(next_checkpoint),
+	NILFS_CHECKPOINTS_ATTR_LIST(README),
+	NULL,
+};
+
+NILFS_DEV_INT_GROUP_OPS(checkpoints, dev);
+NILFS_DEV_INT_GROUP_TYPE(checkpoints, dev);
+NILFS_DEV_INT_GROUP_FNS(checkpoints, dev);
+
 /************************************************************************
  *                        NILFS segments attrs                          *
  ************************************************************************/
@@ -753,10 +866,14 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
 	if (err)
 		goto free_dev_subgroups;
 
-	err = nilfs_sysfs_create_segments_group(nilfs);
+	err = nilfs_sysfs_create_checkpoints_group(nilfs);
 	if (err)
 		goto cleanup_dev_kobject;
 
+	err = nilfs_sysfs_create_segments_group(nilfs);
+	if (err)
+		goto delete_checkpoints_group;
+
 	err = nilfs_sysfs_create_superblock_group(nilfs);
 	if (err)
 		goto delete_segments_group;
@@ -773,6 +890,9 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
 delete_segments_group:
 	nilfs_sysfs_delete_segments_group(nilfs);
 
+delete_checkpoints_group:
+	nilfs_sysfs_delete_checkpoints_group(nilfs);
+
 cleanup_dev_kobject:
 	kobject_del(&nilfs->ns_dev_kobj);
 
@@ -785,6 +905,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
 
 void nilfs_sysfs_delete_device_group(struct the_nilfs *nilfs)
 {
+	nilfs_sysfs_delete_checkpoints_group(nilfs);
 	nilfs_sysfs_delete_segments_group(nilfs);
 	nilfs_sysfs_delete_superblock_group(nilfs);
 	nilfs_sysfs_delete_segctor_group(nilfs);

fs/nilfs2/sysfs.h

@@ -30,6 +30,8 @@
  * @sg_superblock_kobj_unregister: completion state
  * @sg_segctor_kobj: /sys/fs/<nilfs>/<device>/segctor
  * @sg_segctor_kobj_unregister: completion state
+ * @sg_checkpoints_kobj: /sys/fs/<nilfs>/<device>/checkpoints
+ * @sg_checkpoints_kobj_unregister: completion state
  * @sg_segments_kobj: /sys/fs/<nilfs>/<device>/segments
  * @sg_segments_kobj_unregister: completion state
  */
@@ -42,6 +44,10 @@ struct nilfs_sysfs_dev_subgroups {
 	struct kobject sg_segctor_kobj;
 	struct completion sg_segctor_kobj_unregister;
 
+	/* /sys/fs/<nilfs>/<device>/checkpoints */
+	struct kobject sg_checkpoints_kobj;
+	struct completion sg_checkpoints_kobj_unregister;
+
 	/* /sys/fs/<nilfs>/<device>/segments */
 	struct kobject sg_segments_kobj;
 	struct completion sg_segments_kobj_unregister;
@@ -69,6 +75,7 @@ struct nilfs_##name##_attr { \
 
 NILFS_DEV_ATTR_STRUCT(dev);
 NILFS_DEV_ATTR_STRUCT(segments);
+NILFS_DEV_ATTR_STRUCT(checkpoints);
 NILFS_DEV_ATTR_STRUCT(superblock);
 NILFS_DEV_ATTR_STRUCT(segctor);
 
@@ -104,6 +111,11 @@ NILFS_DEV_ATTR_STRUCT(segctor);
 #define NILFS_SEGMENTS_RW_ATTR(name) \
 	NILFS_RW_ATTR(segs_info, name)
 
+#define NILFS_CHECKPOINTS_RO_ATTR(name) \
+	NILFS_RO_ATTR(checkpoints, name)
+#define NILFS_CHECKPOINTS_RW_ATTR(name) \
+	NILFS_RW_ATTR(checkpoints, name)
+
 #define NILFS_SUPERBLOCK_RO_ATTR(name) \
 	NILFS_RO_ATTR(superblock, name)
 #define NILFS_SUPERBLOCK_RW_ATTR(name) \
@@ -122,6 +134,8 @@ NILFS_DEV_ATTR_STRUCT(segctor);
 	(&nilfs_dev_attr_##name.attr)
 #define NILFS_SEGMENTS_ATTR_LIST(name) \
 	(&nilfs_segments_attr_##name.attr)
+#define NILFS_CHECKPOINTS_ATTR_LIST(name) \
+	(&nilfs_checkpoints_attr_##name.attr)
 #define NILFS_SUPERBLOCK_ATTR_LIST(name) \
 	(&nilfs_superblock_attr_##name.attr)
 #define NILFS_SEGCTOR_ATTR_LIST(name) \