exfat: retain 'VolumeFlags' properly

MediaFailure and VolumeDirty should be retained if these are set before
mounting.

In '3.1.13.3 Media Failure Field' of exfat specification describe:

 If, upon mounting a volume, the value of this field is 1,
 implementations which scan the entire volume for media failures and
 record all failures as "bad" clusters in the FAT (or otherwise resolve
 media failures) may clear the value of  this field to 0.

Therefore, We should not clear MediaFailure without scanning volume.

In '8.1 Recommended Write Ordering' of exfat specification describe:

 Clear the value of the VolumeDirty field to 0, if its value prior to
 the first step was 0.

Therefore, We should not clear VolumeDirty after mounting.
Also rename ERR_MEDIUM to MEDIA_FAILURE.

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

1 files changed, 27 insertions, 9 deletions

diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index b5bf6dedbe11..3b6a1659892f 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -63,7 +63,7 @@ static int exfat_sync_fs(struct super_block *sb, int wait)
 	/* If there are some dirty buffers in the bdev inode */
 	mutex_lock(&sbi->s_lock);
 	sync_blockdev(sb->s_bdev);
-	if (exfat_set_vol_flags(sb, VOL_CLEAN))
+	if (exfat_clear_volume_dirty(sb))
 		err = -EIO;
 	mutex_unlock(&sbi->s_lock);
 	return err;
@@ -96,17 +96,20 @@ static int exfat_statfs(struct dentry *dentry, struct kstatfs *buf)
 	return 0;
 }
 
-int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
+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;
+
 	/* flags are not changed */
-	if (sbi->vol_flag == new_flag)
+	if (sbi->vol_flags == new_flags)
 		return 0;
 
-	sbi->vol_flag = new_flag;
+	sbi->vol_flags = new_flags;
 
 	/* skip updating volume dirty flag,
 	 * if this volume has been mounted with read-only
@@ -114,9 +117,9 @@ int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
 	if (sb_rdonly(sb))
 		return 0;
 
-	p_boot->vol_flags = cpu_to_le16(new_flag);
+	p_boot->vol_flags = cpu_to_le16(new_flags);
 
-	if (new_flag == VOL_DIRTY && !buffer_dirty(sbi->boot_bh))
+	if ((new_flags & VOLUME_DIRTY) && !buffer_dirty(sbi->boot_bh))
 		sync = true;
 	else
 		sync = false;
@@ -129,6 +132,20 @@ int exfat_set_vol_flags(struct super_block *sb, unsigned short new_flag)
 	return 0;
 }
 
+int exfat_set_volume_dirty(struct super_block *sb)
+{
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	return exfat_set_vol_flags(sb, sbi->vol_flags | VOLUME_DIRTY);
+}
+
+int exfat_clear_volume_dirty(struct super_block *sb)
+{
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	return exfat_set_vol_flags(sb, sbi->vol_flags & ~VOLUME_DIRTY);
+}
+
 static int exfat_show_options(struct seq_file *m, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
@@ -457,7 +474,8 @@ static int exfat_read_boot_sector(struct super_block *sb)
 	sbi->dentries_per_clu = 1 <<
 		(sbi->cluster_size_bits - DENTRY_SIZE_BITS);
 
-	sbi->vol_flag = le16_to_cpu(p_boot->vol_flags);
+	sbi->vol_flags = le16_to_cpu(p_boot->vol_flags);
+	sbi->vol_flags_persistent = sbi->vol_flags & (VOLUME_DIRTY | MEDIA_FAILURE);
 	sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
 	sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
 
@@ -472,9 +490,9 @@ static int exfat_read_boot_sector(struct super_block *sb)
 		exfat_err(sb, "bogus data start sector");
 		return -EINVAL;
 	}
-	if (sbi->vol_flag & VOL_DIRTY)
+	if (sbi->vol_flags & VOLUME_DIRTY)
 		exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");
-	if (sbi->vol_flag & ERR_MEDIUM)
+	if (sbi->vol_flags & MEDIA_FAILURE)
 		exfat_warn(sb, "Medium has reported failures. Some data may be lost.");
 
 	/* exFAT file size is limited by a disk volume size */