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

Signed-off-by: Ethan Ferguson <ethan.ferguson@zetier.com>
---
 fs/fat/fat.h   |  1 +
 fs/fat/file.c  |  9 +++++++++
 fs/fat/inode.c | 11 +++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index d3e426de5f01..db9c854ddef8 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 4fc49a614fb8..c55a99009a9c 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -153,6 +153,13 @@ static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 	return 0;
 }
 
+static int fat_ioctl_get_volume_label(struct inode *inode, char __user *arg)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
+	return copy_to_user(arg, sbi->vol_label, MSDOS_NAME);
+}
+
 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -165,6 +172,8 @@ 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, (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 0b6009cd1844..f6bd3f079e74 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));
-- 
2.53.0

Hi Ethan,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Ethan-Ferguson/fat-Add-FS_IOC_GETFSLABEL-ioctl/20260211-062606
base:   9f2693489ef8558240d9e80bfad103650daed0af
patch link:    https://lore.kernel.org/r/20260210222310.357755-2-ethan.ferguson%40zetier.com
patch subject: [PATCH 1/2] fat: Add FS_IOC_GETFSLABEL ioctl
config: riscv-randconfig-r071-20260211 (https://download.01.org/0day-ci/archive/20260211/202602111747.QIBXIwpw-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 9.5.0
smatch version: v0.5.0-8994-gd50c5a4c

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202602111747.QIBXIwpw-lkp@intel.com/

smatch warnings:
fs/fat/file.c:160 fat_ioctl_get_volume_label() warn: maybe return -EFAULT instead of the bytes remaining?

vim +160 fs/fat/file.c

5fc1746d68b8fb Ethan Ferguson 2026-02-10  156  static int fat_ioctl_get_volume_label(struct inode *inode, char __user *arg)
5fc1746d68b8fb Ethan Ferguson 2026-02-10  157  {
5fc1746d68b8fb Ethan Ferguson 2026-02-10  158  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
5fc1746d68b8fb Ethan Ferguson 2026-02-10  159  
5fc1746d68b8fb Ethan Ferguson 2026-02-10 @160  	return copy_to_user(arg, sbi->vol_label, MSDOS_NAME);

This should be:

	if (copy_to_user(arg, sbi->vol_label, MSDOS_NAME))
		return -EFAULT;

	return 0;

5fc1746d68b8fb Ethan Ferguson 2026-02-10  161  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki