[PATCH v5 1/2] fs: fat: Add fat filesystem partition volume label in local structure

[ChenGuanqiao]

1. Read volume label whe the fat system driver load.
2. Add interface to scan volume label entry.

Signed-off-by: ChenGuanqiao <chen.chenchacha@xxxxxxxxxxx>
---
 fs/fat/dir.c                  | 29 +++++++++++++++++++++++++++++
 fs/fat/fat.h                  |  2 ++
 fs/fat/inode.c                | 15 ++++++++++++---
 include/uapi/linux/msdos_fs.h |  2 ++
 4 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 81cecbe6d7cf..b369953979e3 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -881,6 +881,35 @@ static int fat_get_short_entry(struct inode *dir, loff_t *pos,
 	return -ENOENT;
 }
 
+static int fat_get_volume_label_entry(struct inode *dir, loff_t *pos,
+			       struct buffer_head **bh,
+			       struct msdos_dir_entry **de)
+{
+	while (fat_get_entry(dir, pos, bh, de) >= 0)
+		if (((*de)->attr & ATTR_VOLUME) && (*de)->attr != ATTR_EXT)
+			return 0;
+	return -ENOENT;
+}
+
+int fat_scan_volume_label(struct inode *dir, struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = dir->i_sb;
+
+	sinfo->slot_off = 0;
+	sinfo->bh = NULL;
+	while (fat_get_volume_label_entry(dir, &sinfo->slot_off,
+					  &sinfo->bh, &sinfo->de) >= 0) {
+		sinfo->slot_off -= sizeof(*sinfo->de);
+		sinfo->nr_slots = 1;
+		sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
+
+		return 0;
+	}
+
+	return -ENOENT;
+}
+EXPORT_SYMBOL_GPL(fat_scan_volume_label);
+
 /*
  * The ".." entry can not provide the "struct fat_slot_info" information
  * for inode, nor a usable i_pos. So, this function provides some information
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 051dac1ce3be..9e8d525d52c9 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -85,6 +85,7 @@ 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[11];		/*volume label*/
 
 	int fatent_shift;
 	const struct fatent_operations *fatent_ops;
@@ -299,6 +300,7 @@ extern int fat_dir_empty(struct inode *dir);
 extern int fat_subdirs(struct inode *dir);
 extern int fat_scan(struct inode *dir, const unsigned char *name,
 		    struct fat_slot_info *sinfo);
+extern int fat_scan_volume_label(struct inode *dir, struct fat_slot_info *sinfo);
 extern int fat_scan_logstart(struct inode *dir, int i_logstart,
 			     struct fat_slot_info *sinfo);
 extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 30c52394a7ad..e73379a41d49 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -45,12 +45,14 @@ struct fat_bios_param_block {
 
 	u8	fat16_state;
 	u32	fat16_vol_id;
+	u8	fat16_vol_label[11];
 
 	u32	fat32_length;
 	u32	fat32_root_cluster;
 	u16	fat32_info_sector;
 	u8	fat32_state;
 	u32	fat32_vol_id;
+	u8	fat32_vol_label[11];
 };
 
 static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
@@ -1460,12 +1462,16 @@ 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,
+		   sizeof(bpb->fat16_vol_label));
 
 	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,
+		   sizeof(bpb->fat32_vol_label));
 
 	/* Validate this looks like a FAT filesystem BPB */
 	if (!bpb->fat_reserved) {
@@ -1723,11 +1729,14 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
 		brelse(fsinfo_bh);
 	}
 
-	/* interpret volume ID as a little endian 32 bit integer */
-	if (sbi->fat_bits == 32)
+	/* interpret volume ID and label as a little endian 32 bit integer */
+	if (sbi->fat_bits == 32) {
 		sbi->vol_id = bpb.fat32_vol_id;
-	else /* fat 16 or 12 */
+		memcpy(sbi->vol_label, bpb.fat32_vol_label, sizeof(sbi->vol_label));
+	} else { /* fat 16 or 12 */
 		sbi->vol_id = bpb.fat16_vol_id;
+		memcpy(sbi->vol_label, bpb.fat16_vol_label, sizeof(sbi->vol_label));
+	}
 
 	sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
 	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
diff --git a/include/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
index e956704f5fb1..b4fced0988a9 100644
--- a/include/uapi/linux/msdos_fs.h
+++ b/include/uapi/linux/msdos_fs.h
@@ -106,6 +106,8 @@ struct __fat_dirent {
 #define FAT_IOCTL_SET_ATTRIBUTES	_IOW('r', 0x11, __u32)
 /*Android kernel has used 0x12, so we use 0x13*/
 #define FAT_IOCTL_GET_VOLUME_ID		_IOR('r', 0x13, __u32)
+#define FAT_IOCTL_GET_VOLUME_LABEL	_IOR('r', 0x14, __u8[11])
+#define FAT_IOCTL_SET_VOLUME_LABEL	_IOW('r', 0x15, __u8[11])
 
 struct fat_boot_sector {
 	__u8	ignored[3];	/* Boot strap short or near jump */
-- 
2.11.0