[PATCH v2 1/2] fat: Add FS_IOC_GETFSLABEL ioctl

[Ethan Ferguson]

Add support for reading the volume label of a FAT filesystem via the
FS_IOC_GETFSLABEL ioctl.

Signed-off-by: Ethan Ferguson <ethan.ferguson@xxxxxxxxxx>
---
 fs/fat/fat.h   |  1 +
 fs/fat/file.c  | 16 ++++++++++++++++
 fs/fat/inode.c | 11 +++++++++--
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 0d269dba897b..4350c00dba34 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -89,6 +89,7 @@ struct msdos_sb_info {
 	int dir_per_block;	      /* dir entries per block */
 	int dir_per_block_bits;	      /* log2(dir_per_block) */
 	unsigned int vol_id;		/*volume ID*/
+	char vol_label[MSDOS_NAME];           /* volume label */
 
 	int fatent_shift;
 	const struct fatent_operations *fatent_ops;
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 124d9c5431c8..029b1750d1ec 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -153,6 +153,20 @@ static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 	return 0;
 }
 
+static int fat_ioctl_get_volume_label(struct super_block *sb, char __user *arg)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int ret;
+
+	mutex_lock(&sbi->s_lock);
+	ret = copy_to_user(arg, sbi->vol_label, MSDOS_NAME);
+	mutex_unlock(&sbi->s_lock);
+	if (ret)
+		return -EFAULT;
+
+	return 0;
+}
+
 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -165,6 +179,8 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return fat_ioctl_set_attributes(filp, user_attr);
 	case FAT_IOCTL_GET_VOLUME_ID:
 		return fat_ioctl_get_volume_id(inode, user_attr);
+	case FS_IOC_GETFSLABEL:
+		return fat_ioctl_get_volume_label(inode->i_sb, (char __user *) arg);
 	case FITRIM:
 		return fat_ioctl_fitrim(inode, arg);
 	default:
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 59fa90617b5b..6f9a8cc1ad2a 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -53,12 +53,14 @@ struct fat_bios_param_block {
 
 	u8	fat16_state;
 	u32	fat16_vol_id;
+	u8	fat16_vol_label[MSDOS_NAME];
 
 	u32	fat32_length;
 	u32	fat32_root_cluster;
 	u16	fat32_info_sector;
 	u8	fat32_state;
 	u32	fat32_vol_id;
+	u8	fat32_vol_label[MSDOS_NAME];
 };
 
 static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
@@ -1406,12 +1408,14 @@ static int fat_read_bpb(struct super_block *sb, struct fat_boot_sector *b,
 
 	bpb->fat16_state = b->fat16.state;
 	bpb->fat16_vol_id = get_unaligned_le32(b->fat16.vol_id);
+	memcpy(bpb->fat16_vol_label, b->fat16.vol_label, MSDOS_NAME);
 
 	bpb->fat32_length = le32_to_cpu(b->fat32.length);
 	bpb->fat32_root_cluster = le32_to_cpu(b->fat32.root_cluster);
 	bpb->fat32_info_sector = le16_to_cpu(b->fat32.info_sector);
 	bpb->fat32_state = b->fat32.state;
 	bpb->fat32_vol_id = get_unaligned_le32(b->fat32.vol_id);
+	memcpy(bpb->fat32_vol_label, b->fat32.vol_label, MSDOS_NAME);
 
 	/* Validate this looks like a FAT filesystem BPB */
 	if (!bpb->fat_reserved) {
@@ -1708,10 +1712,13 @@ int fat_fill_super(struct super_block *sb, struct fs_context *fc,
 	}
 
 	/* interpret volume ID as a little endian 32 bit integer */
-	if (is_fat32(sbi))
+	if (is_fat32(sbi)) {
 		sbi->vol_id = bpb.fat32_vol_id;
-	else /* fat 16 or 12 */
+		memcpy(sbi->vol_label, bpb.fat32_vol_label, MSDOS_NAME);
+	} else { /* fat 16 or 12 */
 		sbi->vol_id = bpb.fat16_vol_id;
+		memcpy(sbi->vol_label, bpb.fat16_vol_label, MSDOS_NAME);
+	}
 
 	__le32 vol_id_le = cpu_to_le32(sbi->vol_id);
 	super_set_uuid(sb, (void *) &vol_id_le, sizeof(vol_id_le));
-- 
2.43.0