f2fs: skip committing valid superblock

In recovery procedure for superblock, we try to write data of valid
superblock into invalid one for recovery, work should be finished here,
but then still we will write the valid one with its original data.
This operation is not needed. Let's skip doing this unnecessary work.
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1624,7 +1624,7 @@ static inline int f2fs_add_link(struct dentry *dentry, struct inode *inode)
 /*
  * super.c
  */
-int f2fs_commit_super(struct f2fs_sb_info *);
+int f2fs_commit_super(struct f2fs_sb_info *, bool);
 int f2fs_sync_fs(struct super_block *, int);
 extern __printf(3, 4)
 void f2fs_msg(struct super_block *, const char *, const char *, ...);

fs/f2fs/file.c

@@ -1530,7 +1530,7 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 	/* update superblock with uuid */
 	generate_random_uuid(sbi->raw_super->encrypt_pw_salt);
 
-	err = f2fs_commit_super(sbi);
+	err = f2fs_commit_super(sbi, false);
 
 	mnt_drop_write_file(filp);
 	if (err) {

fs/f2fs/super.c

@@ -1043,7 +1043,7 @@ static int read_raw_super_block(struct super_block *sb,
 	return 0;
 }
 
-int f2fs_commit_super(struct f2fs_sb_info *sbi)
+int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
 {
 	struct buffer_head *sbh = sbi->raw_super_buf;
 	sector_t block = sbh->b_blocknr;
@@ -1055,7 +1055,9 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi)
 	err = sync_dirty_buffer(sbh);
 
 	sbh->b_blocknr = block;
-	if (err)
+
+	/* if we are in recovery path, skip writing valid superblock */
+	if (recover || err)
 		goto out;
 
 	/* write current valid superblock */
@@ -1289,7 +1291,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	/* recover broken superblock */
 	if (recovery && !f2fs_readonly(sb) && !bdev_read_only(sb->s_bdev)) {
 		f2fs_msg(sb, KERN_INFO, "Recover invalid superblock");
-		f2fs_commit_super(sbi);
+		f2fs_commit_super(sbi, true);
 	}
 
 	return 0;