f2fs: don't grab super block buffer header all the time

We have already got one copy of valid super block in memory, do not grab
buffer header of super block all the time.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -715,8 +715,8 @@ enum {
 struct f2fs_sb_info {
 	struct super_block *sb;			/* pointer to VFS super block */
 	struct proc_dir_entry *s_proc;		/* proc entry */
-	struct buffer_head *raw_super_buf;	/* buffer head of raw sb */
 	struct f2fs_super_block *raw_super;	/* raw super block pointer */
+	int valid_super_block;			/* valid super block no */
 	int s_flag;				/* flags for sbi */
 
 	/* for node-related operations */

fs/f2fs/file.c

@@ -1591,20 +1591,16 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 		return err;
 
 	/* update superblock with uuid */
-	lock_buffer(sbi->raw_super_buf);
 	generate_random_uuid(sbi->raw_super->encrypt_pw_salt);
-	unlock_buffer(sbi->raw_super_buf);
 
 	err = f2fs_commit_super(sbi, false);
-
-	mnt_drop_write_file(filp);
 	if (err) {
 		/* undo new data */
-		lock_buffer(sbi->raw_super_buf);
 		memset(sbi->raw_super->encrypt_pw_salt, 0, 16);
-		unlock_buffer(sbi->raw_super_buf);
+		mnt_drop_write_file(filp);
 		return err;
 	}
+	mnt_drop_write_file(filp);
 got_it:
 	if (copy_to_user((__u8 __user *)arg, sbi->raw_super->encrypt_pw_salt,
 									16))

fs/f2fs/super.c

@@ -567,7 +567,6 @@ static void f2fs_put_super(struct super_block *sb)
 	wait_for_completion(&sbi->s_kobj_unregister);
 
 	sb->s_fs_info = NULL;
-	brelse(sbi->raw_super_buf);
 	kfree(sbi->raw_super);
 	kfree(sbi);
 }
@@ -1132,65 +1131,53 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
  */
 static int read_raw_super_block(struct super_block *sb,
 			struct f2fs_super_block **raw_super,
-			struct buffer_head **raw_super_buf,
-			int *recovery)
+			int *valid_super_block, int *recovery)
 {
 	int block = 0;
-	struct buffer_head *buffer;
-	struct f2fs_super_block *super;
+	struct buffer_head *bh;
+	struct f2fs_super_block *super, *buf;
 	int err = 0;
 
 	super = kzalloc(sizeof(struct f2fs_super_block), GFP_KERNEL);
 	if (!super)
 		return -ENOMEM;
 retry:
-	buffer = sb_bread(sb, block);
-	if (!buffer) {
+	bh = sb_bread(sb, block);
+	if (!bh) {
 		*recovery = 1;
 		f2fs_msg(sb, KERN_ERR, "Unable to read %dth superblock",
 				block + 1);
-		if (block == 0) {
-			block++;
-			goto retry;
-		} else {
-			err = -EIO;
-			goto out;
-		}
+		err = -EIO;
+		goto next;
 	}
 
-	memcpy(super, buffer->b_data + F2FS_SUPER_OFFSET, sizeof(*super));
+	buf = (struct f2fs_super_block *)(bh->b_data + F2FS_SUPER_OFFSET);
 
 	/* sanity checking of raw super */
-	if (sanity_check_raw_super(sb, super)) {
-		brelse(buffer);
+	if (sanity_check_raw_super(sb, buf)) {
+		brelse(bh);
 		*recovery = 1;
 		f2fs_msg(sb, KERN_ERR,
 			"Can't find valid F2FS filesystem in %dth superblock",
 								block + 1);
-		if (block == 0) {
-			block++;
-			goto retry;
-		} else {
-			err = -EINVAL;
-			goto out;
-		}
+		err = -EINVAL;
+		goto next;
 	}
 
 	if (!*raw_super) {
-		*raw_super_buf = buffer;
+		memcpy(super, buf, sizeof(*super));
+		*valid_super_block = block;
 		*raw_super = super;
-	} else {
-		/* already have a valid superblock */
-		brelse(buffer);
 	}
+	brelse(bh);
 
+next:
 	/* check the validity of the second superblock */
 	if (block == 0) {
 		block++;
 		goto retry;
 	}
 
-out:
 	/* No valid superblock */
 	if (!*raw_super) {
 		kfree(super);
@@ -1203,18 +1190,16 @@ static int read_raw_super_block(struct super_block *sb,
 int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
 {
 	struct f2fs_super_block *super = F2FS_RAW_SUPER(sbi);
-	struct buffer_head *sbh = sbi->raw_super_buf;
 	struct buffer_head *bh;
 	int err;
 
 	/* write back-up superblock first */
-	bh = sb_getblk(sbi->sb, sbh->b_blocknr ? 0 : 1);
+	bh = sb_getblk(sbi->sb, sbi->valid_super_block ? 0 : 1);
 	if (!bh)
 		return -EIO;
 
 	lock_buffer(bh);
 	memcpy(bh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super));
-	WARN_ON(sbh->b_size != F2FS_BLKSIZE);
 	set_buffer_uptodate(bh);
 	set_buffer_dirty(bh);
 	unlock_buffer(bh);
@@ -1227,33 +1212,37 @@ int f2fs_commit_super(struct f2fs_sb_info *sbi, bool recover)
 	if (recover || err)
 		return err;
 
+	bh = sb_getblk(sbi->sb, sbi->valid_super_block);
+	if (!bh)
+		return -EIO;
+
 	/* write current valid superblock */
-	lock_buffer(sbh);
-	if (memcmp(sbh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super))) {
-		f2fs_msg(sbi->sb, KERN_INFO, "Write modified valid superblock");
-		memcpy(sbh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super));
-	}
-	set_buffer_dirty(sbh);
-	unlock_buffer(sbh);
+	lock_buffer(bh);
+	memcpy(bh->b_data + F2FS_SUPER_OFFSET, super, sizeof(*super));
+	set_buffer_uptodate(bh);
+	set_buffer_dirty(bh);
+	unlock_buffer(bh);
 
-	return __sync_dirty_buffer(sbh, WRITE_FLUSH_FUA);
+	err = __sync_dirty_buffer(bh, WRITE_FLUSH_FUA);
+	brelse(bh);
+
+	return err;
 }
 
 static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct f2fs_sb_info *sbi;
 	struct f2fs_super_block *raw_super;
-	struct buffer_head *raw_super_buf;
 	struct inode *root;
 	long err;
 	bool retry = true, need_fsck = false;
 	char *options = NULL;
-	int recovery, i;
+	int recovery, i, valid_super_block;
 
 try_onemore:
 	err = -EINVAL;
 	raw_super = NULL;
-	raw_super_buf = NULL;
+	valid_super_block = -1;
 	recovery = 0;
 
 	/* allocate memory for f2fs-specific super block info */
@@ -1267,7 +1256,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 		goto free_sbi;
 	}
 
-	err = read_raw_super_block(sb, &raw_super, &raw_super_buf, &recovery);
+	err = read_raw_super_block(sb, &raw_super, &valid_super_block,
+								&recovery);
 	if (err)
 		goto free_sbi;
 
@@ -1300,7 +1290,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	/* init f2fs-specific super block info */
 	sbi->sb = sb;
 	sbi->raw_super = raw_super;
-	sbi->raw_super_buf = raw_super_buf;
+	sbi->valid_super_block = valid_super_block;
 	mutex_init(&sbi->gc_mutex);
 	mutex_init(&sbi->writepages);
 	mutex_init(&sbi->cp_mutex);
@@ -1506,7 +1496,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 free_options:
 	kfree(options);
 free_sb_buf:
-	brelse(raw_super_buf);
 	kfree(raw_super);
 free_sbi:
 	kfree(sbi);