nilfs2: embed a back pointer to super block instance in nilfs object

Insert a back pointer to super block instance in nilfs object so that
functions of nilfs2 easily refer to the super block instance.  This
simplifies replacement of printk() in the successive change.

Link: http://lkml.kernel.org/r/1464875891-5443-4-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/super.c

@@ -1076,7 +1076,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent)
 	__u64 cno;
 	int err;
 
-	nilfs = alloc_nilfs(sb->s_bdev);
+	nilfs = alloc_nilfs(sb);
 	if (!nilfs)
 		return -ENOMEM;
 

fs/nilfs2/the_nilfs.c

@@ -56,12 +56,12 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
 
 /**
  * alloc_nilfs - allocate a nilfs object
- * @bdev: block device to which the_nilfs is related
+ * @sb: super block instance
  *
  * Return Value: On success, pointer to the_nilfs is returned.
  * On error, NULL is returned.
  */
-struct the_nilfs *alloc_nilfs(struct block_device *bdev)
+struct the_nilfs *alloc_nilfs(struct super_block *sb)
 {
 	struct the_nilfs *nilfs;
 
@@ -69,7 +69,8 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
 	if (!nilfs)
 		return NULL;
 
-	nilfs->ns_bdev = bdev;
+	nilfs->ns_sb = sb;
+	nilfs->ns_bdev = sb->s_bdev;
 	atomic_set(&nilfs->ns_ndirtyblks, 0);
 	init_rwsem(&nilfs->ns_sem);
 	mutex_init(&nilfs->ns_snapshot_mount_mutex);

fs/nilfs2/the_nilfs.h

@@ -43,6 +43,7 @@ enum {
  * struct the_nilfs - struct to supervise multiple nilfs mount points
  * @ns_flags: flags
  * @ns_flushed_device: flag indicating if all volatile data was flushed
+ * @ns_sb: back pointer to super block instance
  * @ns_bdev: block device
  * @ns_sem: semaphore for shared states
  * @ns_snapshot_mount_mutex: mutex to protect snapshot mounts
@@ -102,6 +103,7 @@ struct the_nilfs {
 	unsigned long		ns_flags;
 	int			ns_flushed_device;
 
+	struct super_block     *ns_sb;
 	struct block_device    *ns_bdev;
 	struct rw_semaphore	ns_sem;
 	struct mutex		ns_snapshot_mount_mutex;
@@ -281,7 +283,7 @@ static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)
 }
 
 void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
-struct the_nilfs *alloc_nilfs(struct block_device *bdev);
+struct the_nilfs *alloc_nilfs(struct super_block *sb);
 void destroy_nilfs(struct the_nilfs *nilfs);
 int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data);
 int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb);