exfat: do not clear VolumeDirty in writeback

Before this commit, VolumeDirty will be cleared first in
writeback if 'dirsync' or 'sync' is not enabled. If the power
is suddenly cut off after cleaning VolumeDirty but other
updates are not written, the exFAT filesystem will not be able
to detect the power failure in the next mount.

And VolumeDirty will be set again but not cleared when updating
the parent directory. It means that BootSector will be written at
least once in each write-back, which will shorten the life of the
device.

Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@sony.com>
Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: YuezhangMo

fs/exfat/file.c

@@ -218,8 +218,6 @@ int __exfat_truncate(struct inode *inode, loff_t new_size)
 	if (exfat_free_cluster(inode, &clu))
 		return -EIO;
 
-	exfat_clear_volume_dirty(sb);
-
 	return 0;
 }
 

fs/exfat/namei.c

@@ -576,7 +576,6 @@ static int exfat_create(struct user_namespace *mnt_userns, struct inode *dir,
 	exfat_set_volume_dirty(sb);
 	err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_FILE,
 		&info);
-	exfat_clear_volume_dirty(sb);
 	if (err)
 		goto unlock;
 
@@ -834,7 +833,6 @@ static int exfat_unlink(struct inode *dir, struct dentry *dentry)
 
 	/* This doesn't modify ei */
 	ei->dir.dir = DIR_DELETED;
-	exfat_clear_volume_dirty(sb);
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
@@ -868,7 +866,6 @@ static int exfat_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 	exfat_set_volume_dirty(sb);
 	err = exfat_add_entry(dir, dentry->d_name.name, &cdir, TYPE_DIR,
 		&info);
-	exfat_clear_volume_dirty(sb);
 	if (err)
 		goto unlock;
 
@@ -998,7 +995,6 @@ static int exfat_rmdir(struct inode *dir, struct dentry *dentry)
 		goto unlock;
 	}
 	ei->dir.dir = DIR_DELETED;
-	exfat_clear_volume_dirty(sb);
 
 	inode_inc_iversion(dir);
 	dir->i_mtime = dir->i_atime = current_time(dir);
@@ -1333,7 +1329,6 @@ static int __exfat_rename(struct inode *old_parent_inode,
 		 */
 		new_ei->dir.dir = DIR_DELETED;
 	}
-	exfat_clear_volume_dirty(sb);
 out:
 	return ret;
 }

fs/exfat/super.c

@@ -100,7 +100,6 @@ static int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flags)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct boot_sector *p_boot = (struct boot_sector *)sbi->boot_bh->b_data;
-	bool sync;
 
 	/* retain persistent-flags */
 	new_flags |= sbi->vol_flags_persistent;
@@ -119,16 +118,11 @@ static int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flags)
 
 	p_boot->vol_flags = cpu_to_le16(new_flags);
 
-	if ((new_flags & VOLUME_DIRTY) && !buffer_dirty(sbi->boot_bh))
-		sync = true;
-	else
-		sync = false;
-
 	set_buffer_uptodate(sbi->boot_bh);
 	mark_buffer_dirty(sbi->boot_bh);
 
-	if (sync)
-		sync_dirty_buffer(sbi->boot_bh);
+	__sync_dirty_buffer(sbi->boot_bh, REQ_SYNC | REQ_FUA | REQ_PREFLUSH);
+
 	return 0;
 }