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

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

The superblock group contains attributes that describe
superblock's details:
(1) sb_write_time - show previous write time of super block in
human-readable format.
(2) sb_write_time_secs - show previous write time of super block
in seconds.
(3) sb_write_count - show write count of super block.
(4) sb_update_frequency - show/set interval of periodical update
of superblock (in seconds). You can set preferable frequency of
superblock update by command:

echo <value> > /sys/fs/nilfs2/<device>/superblock/sb_update_frequency

Signed-off-by: Vyacheslav 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 34bc7bd..7fe8223 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 
 struct nilfs_sc_info;
+struct nilfs_sysfs_dev_subgroups;
 
 /* the_nilfs struct */
 enum {
@@ -54,6 +55,7 @@ enum {
  * @ns_sbwcount: write count of super block
  * @ns_sbsize: size of valid data in super block
  * @ns_mount_state: file system state
+ * @ns_sb_update_freq: interval of periodical update of superblocks (in seconds)
  * @ns_seg_seq: segment sequence counter
  * @ns_segnum: index number of the latest full segment.
  * @ns_nextnum: index number of the full segment index to be used next
@@ -97,6 +99,7 @@ enum {
  * @ns_crc_seed: seed value of CRC32 calculation
  * @ns_dev_kobj: /sys/fs/<nilfs>/<device>
  * @ns_dev_kobj_unregister: completion state
+ * @ns_dev_subgroups: <device> subgroups pointer
  */
 struct the_nilfs {
 	unsigned long		ns_flags;
@@ -116,6 +119,7 @@ struct the_nilfs {
 	unsigned		ns_sbwcount;
 	unsigned		ns_sbsize;
 	unsigned		ns_mount_state;
+	unsigned		ns_sb_update_freq;
 
 	/*
 	 * Following fields are dedicated to a writable FS-instance.
@@ -194,6 +198,7 @@ struct the_nilfs {
 	/* /sys/fs/<nilfs>/<device> */
 	struct kobject ns_dev_kobj;
 	struct completion ns_dev_kobj_unregister;
+	struct nilfs_sysfs_dev_subgroups *ns_dev_subgroups;
 };
 
 #define THE_NILFS_FNS(bit, name)					\
@@ -260,7 +265,8 @@ struct nilfs_root {
 static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
 {
 	u64 t = get_seconds();
-	return t < nilfs->ns_sbwtime || t > nilfs->ns_sbwtime + NILFS_SB_FREQ;
+	return t < nilfs->ns_sbwtime ||
+		t > nilfs->ns_sbwtime + nilfs->ns_sb_update_freq;
 }
 
 static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)