exfat: Add support for FS_IOC_{GET,SET}FSLABEL

Add support for reading / writing to the exfat volume label from the
FS_IOC_GETFSLABEL and FS_IOC_SETFSLABEL ioctls

Co-developed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Ethan Ferguson <ethan.ferguson@zetier.com>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

fs/exfat/dir.c

@@ -1244,3 +1244,163 @@ int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir)
 
 	return count;
 }
+
+static int exfat_get_volume_label_dentry(struct super_block *sb,
+		struct exfat_entry_set_cache *es)
+{
+	int i;
+	int dentry = 0;
+	unsigned int type;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_hint_femp hint_femp;
+	struct exfat_inode_info *ei = EXFAT_I(sb->s_root->d_inode);
+	struct exfat_chain clu;
+	struct exfat_dentry *ep;
+	struct buffer_head *bh;
+
+	hint_femp.eidx = EXFAT_HINT_NONE;
+	exfat_chain_set(&clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
+
+	while (clu.dir != EXFAT_EOF_CLUSTER) {
+		for (i = 0; i < sbi->dentries_per_clu; i++, dentry++) {
+			ep = exfat_get_dentry(sb, &clu, i, &bh);
+			if (!ep)
+				return -EIO;
+
+			type = exfat_get_entry_type(ep);
+			if (hint_femp.eidx == EXFAT_HINT_NONE) {
+				if (type == TYPE_DELETED || type == TYPE_UNUSED) {
+					hint_femp.cur = clu;
+					hint_femp.eidx = dentry;
+					hint_femp.count = 1;
+				}
+			}
+
+			if (type == TYPE_UNUSED) {
+				brelse(bh);
+				goto not_found;
+			}
+
+			if (type != TYPE_VOLUME) {
+				brelse(bh);
+				continue;
+			}
+
+			memset(es, 0, sizeof(*es));
+			es->sb = sb;
+			es->bh = es->__bh;
+			es->bh[0] = bh;
+			es->num_bh = 1;
+			es->start_off = EXFAT_DEN_TO_B(i) % sb->s_blocksize;
+
+			return 0;
+		}
+
+		if (exfat_get_next_cluster(sb, &(clu.dir)))
+			return -EIO;
+	}
+
+not_found:
+	if (hint_femp.eidx == EXFAT_HINT_NONE) {
+		hint_femp.cur.dir = EXFAT_EOF_CLUSTER;
+		hint_femp.eidx = dentry;
+		hint_femp.count = 0;
+	}
+
+	ei->hint_femp = hint_femp;
+
+	return -ENOENT;
+}
+
+int exfat_read_volume_label(struct super_block *sb, struct exfat_uni_name *label_out)
+{
+	int ret, i;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_entry_set_cache es;
+	struct exfat_dentry *ep;
+
+	mutex_lock(&sbi->s_lock);
+
+	memset(label_out, 0, sizeof(*label_out));
+	ret = exfat_get_volume_label_dentry(sb, &es);
+	if (ret < 0) {
+		/*
+		 * ENOENT signifies that a volume label dentry doesn't exist
+		 * We will treat this as an empty volume label and not fail.
+		 */
+		if (ret == -ENOENT)
+			ret = 0;
+
+		goto unlock;
+	}
+
+	ep = exfat_get_dentry_cached(&es, 0);
+	label_out->name_len = ep->dentry.volume_label.char_count;
+	if (label_out->name_len > EXFAT_VOLUME_LABEL_LEN) {
+		ret = -EIO;
+		exfat_put_dentry_set(&es, false);
+		goto unlock;
+	}
+
+	for (i = 0; i < label_out->name_len; i++)
+		label_out->name[i] = le16_to_cpu(ep->dentry.volume_label.volume_label[i]);
+
+	exfat_put_dentry_set(&es, false);
+unlock:
+	mutex_unlock(&sbi->s_lock);
+	return ret;
+}
+
+int exfat_write_volume_label(struct super_block *sb,
+			     struct exfat_uni_name *label)
+{
+	int ret, i;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct inode *root_inode = sb->s_root->d_inode;
+	struct exfat_entry_set_cache es;
+	struct exfat_chain clu;
+	struct exfat_dentry *ep;
+
+	if (label->name_len > EXFAT_VOLUME_LABEL_LEN)
+		return -EINVAL;
+
+	mutex_lock(&sbi->s_lock);
+
+	ret = exfat_get_volume_label_dentry(sb, &es);
+	if (ret == -ENOENT) {
+		if (label->name_len == 0) {
+			/* No volume label dentry, no need to clear */
+			ret = 0;
+			goto unlock;
+		}
+
+		ret = exfat_find_empty_entry(root_inode, &clu, 1, &es);
+	}
+
+	if (ret < 0)
+		goto unlock;
+
+	ep = exfat_get_dentry_cached(&es, 0);
+
+	if (label->name_len == 0 && ep->dentry.volume_label.char_count == 0) {
+		/* volume label had been cleared */
+		exfat_put_dentry_set(&es, 0);
+		goto unlock;
+	}
+
+	memset(ep, 0, sizeof(*ep));
+	ep->type = EXFAT_VOLUME;
+
+	for (i = 0; i < label->name_len; i++)
+		ep->dentry.volume_label.volume_label[i] =
+			cpu_to_le16(label->name[i]);
+
+	ep->dentry.volume_label.char_count = label->name_len;
+	es.modified = true;
+
+	ret = exfat_put_dentry_set(&es, IS_DIRSYNC(root_inode));
+
+unlock:
+	mutex_unlock(&sbi->s_lock);
+	return ret;
+}

fs/exfat/exfat_fs.h

@@ -477,6 +477,9 @@ int exfat_force_shutdown(struct super_block *sb, u32 flags);
 /* namei.c */
 extern const struct dentry_operations exfat_dentry_ops;
 extern const struct dentry_operations exfat_utf8_dentry_ops;
+int exfat_find_empty_entry(struct inode *inode,
+		struct exfat_chain *p_dir, int num_entries,
+			   struct exfat_entry_set_cache *es);
 
 /* cache.c */
 int exfat_cache_init(void);
@@ -517,6 +520,10 @@ int exfat_get_empty_dentry_set(struct exfat_entry_set_cache *es,
 		unsigned int num_entries);
 int exfat_put_dentry_set(struct exfat_entry_set_cache *es, int sync);
 int exfat_count_dir_entries(struct super_block *sb, struct exfat_chain *p_dir);
+int exfat_read_volume_label(struct super_block *sb,
+			    struct exfat_uni_name *label_out);
+int exfat_write_volume_label(struct super_block *sb,
+			     struct exfat_uni_name *label);
 
 /* inode.c */
 extern const struct inode_operations exfat_file_inode_operations;

fs/exfat/exfat_raw.h

@@ -80,6 +80,7 @@
 #define BOOTSEC_OLDBPB_LEN		53
 
 #define EXFAT_FILE_NAME_LEN		15
+#define EXFAT_VOLUME_LABEL_LEN		11
 
 #define EXFAT_MIN_SECT_SIZE_BITS		9
 #define EXFAT_MAX_SECT_SIZE_BITS		12
@@ -159,6 +160,11 @@ struct exfat_dentry {
 			__le32 start_clu;
 			__le64 size;
 		} __packed upcase; /* up-case table directory entry */
+		struct {
+			__u8 char_count;
+			__le16 volume_label[EXFAT_VOLUME_LABEL_LEN];
+			__u8 reserved[8];
+		} __packed volume_label; /* volume label directory entry */
 		struct {
 			__u8 flags;
 			__u8 vendor_guid[16];

fs/exfat/file.c

@@ -486,6 +486,54 @@ static int exfat_ioctl_shutdown(struct super_block *sb, unsigned long arg)
 	return exfat_force_shutdown(sb, flags);
 }
 
+static int exfat_ioctl_get_volume_label(struct super_block *sb, unsigned long arg)
+{
+	int ret;
+	char label[FSLABEL_MAX] = {0};
+	struct exfat_uni_name uniname;
+
+	ret = exfat_read_volume_label(sb, &uniname);
+	if (ret < 0)
+		return ret;
+
+	ret = exfat_utf16_to_nls(sb, &uniname, label, uniname.name_len);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user((char __user *)arg, label, ret + 1))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int exfat_ioctl_set_volume_label(struct super_block *sb,
+					unsigned long arg)
+{
+	int ret = 0, lossy;
+	char label[FSLABEL_MAX];
+	struct exfat_uni_name uniname;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (copy_from_user(label, (char __user *)arg, FSLABEL_MAX))
+		return -EFAULT;
+
+	memset(&uniname, 0, sizeof(uniname));
+	if (label[0]) {
+		ret = exfat_nls_to_utf16(sb, label, FSLABEL_MAX,
+					 &uniname, &lossy);
+		if (ret < 0)
+			return ret;
+		else if (lossy & NLS_NAME_LOSSY)
+			return -EINVAL;
+	}
+
+	uniname.name_len = ret;
+
+	return exfat_write_volume_label(sb, &uniname);
+}
+
 long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -500,6 +548,10 @@ long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return exfat_ioctl_shutdown(inode->i_sb, arg);
 	case FITRIM:
 		return exfat_ioctl_fitrim(inode, arg);
+	case FS_IOC_GETFSLABEL:
+		return exfat_ioctl_get_volume_label(inode->i_sb, arg);
+	case FS_IOC_SETFSLABEL:
+		return exfat_ioctl_set_volume_label(inode->i_sb, arg);
 	default:
 		return -ENOTTY;
 	}

fs/exfat/namei.c

@@ -300,7 +300,7 @@ static int exfat_check_max_dentries(struct inode *inode)
  *   the directory entry index in p_dir is returned on succeeds
  *   -error code is returned on failure
  */
-static int exfat_find_empty_entry(struct inode *inode,
+int exfat_find_empty_entry(struct inode *inode,
 		struct exfat_chain *p_dir, int num_entries,
 		struct exfat_entry_set_cache *es)
 {