[PATCH v5 0/2] fs: fat: add ioctl to modify fat filesystem partion volume label

[PATCH v5 0/2] fs: fat: add ioctl to modify fat filesystem partion volume label

[ChenGuanqiao]

The FAT filesystem partition volume label can be read with
FAT_IOCTL_GET_VOLUME_LABEL and written with FAT_IOCTL_SET_VOLUME_LABEL.

FAT volume label (volume name) is exactly same stored in boot sector and root
directory. Thus, the boot sector just needs to be upgrade when the label
writing.

v5:
1. find the volume label entry through the scan function.
2. the volume label only retains the d-characters (reference from Ecma-107).

v4:
1. read/write volume label from/to the location of the respective version.
2. correct volume label check reference from mkfs.fat.
3. fixed some code issue.

v3:
1. write volume label both boot sector and root directory.

v2:
1. add filesystem version check.
2. add diretory permissions check.
3. add volume label string check.
4. fixed part of return value.
5. fixed some indent issue.
6. remove sync_dirty_buffer().

ChenGuanqiao (2):
  fs: fat: Add fat filesystem partition volume label in local structure
  fs: fat: add ioctl method in fat filesystem driver

 fs/fat/dir.c                  |  29 +++++++++++
 fs/fat/fat.h                  |   2 +
 fs/fat/file.c                 | 116 ++++++++++++++++++++++++++++++++++++++++++
 fs/fat/inode.c                |  15 ++++--
 include/uapi/linux/msdos_fs.h |   2 +
 5 files changed, 161 insertions(+), 3 deletions(-)

-- 
2.11.0

[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@foxmail.com>
---
 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

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

[OGAWA Hirofumi]

ChenGuanqiao <chen.chenchacha@foxmail.com> writes:

> +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);

Why do you need sinfo?
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

[PATCH v5 2/2] fs: fat: add ioctl method in fat filesystem driver

[ChenGuanqiao]

Signed-off-by: ChenGuanqiao <chen.chenchacha@foxmail.com>
---
 fs/fat/file.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 4724cc9ad650..517941c7bce4 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -15,11 +15,35 @@
 #include <linux/fsnotify.h>
 #include <linux/security.h>
 #include <linux/falloc.h>
+#include <linux/ctype.h>
 #include "fat.h"
 
 static long fat_fallocate(struct file *file, int mode,
 			  loff_t offset, loff_t len);
 
+/* the characters in this field shall be d-characters, and unused byte shall be set to 0x20. */
+static int fat_format_d_characters(char *label, unsigned long len)
+{
+	int i;
+
+	for (i=0; i<len; ++i) {
+		switch (label[i]) {
+		case '0' ... '9':
+		case 'A' ... 'Z':
+		case '_':
+			continue;
+		default:
+			break;
+		}
+		break;
+	}
+
+ 	for (; i<len; ++i)
+		label[i] = 0x20;
+
+	return len;
+}
+
 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
 {
 	u32 attr;
@@ -121,10 +145,98 @@ static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
 	return put_user(sbi->vol_id, user_attr);
 }
 
+static int fat_ioctl_get_volume_label(struct inode *inode,
+				      u8 __user *vol_label)
+{
+	int err = 0;
+	struct fat_slot_info sinfo;
+
+	err = fat_scan_volume_label(inode, &sinfo);
+	if (err)
+		goto out;
+
+	if (copy_to_user(vol_label, sinfo.de->name, MSDOS_NAME))
+		err = -EFAULT;
+
+	brelse(sinfo.bh);
+out:
+	return err;
+}
+
+static int fat_ioctl_set_volume_label(struct file *file,
+				      u8 __user *vol_label)
+{
+	int err = 0;
+	u8 label[MSDOS_NAME];
+	struct buffer_head *bh;
+	struct fat_boot_sector *b;
+	struct fat_slot_info sinfo;
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (copy_from_user(label, vol_label, sizeof(label))) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	fat_format_d_characters(label, sizeof(label));
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+
+	/* Update sector's vol_label */
+	bh = sb_bread(sb, 0);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read boot sector to write volume label");
+		err = -EIO;
+		goto out_drop_file;
+	}
+
+	b = (struct fat_boot_sector *)bh->b_data;
+
+	lock_buffer(bh);
+	if (sbi->fat_bits == 32)
+		memcpy(b->fat32.vol_label, label, sizeof(label));
+	else
+		memcpy(b->fat16.vol_label, label, sizeof(label));
+
+	mark_buffer_dirty(bh);
+	unlock_buffer(bh);
+	err = sync_dirty_buffer(bh);
+	brelse(bh);
+	if (err)
+		goto out_drop_file;
+
+	/* updates root directory's vol_label */
+	err = fat_scan_volume_label(inode, &sinfo);
+	if (err)
+		goto out_drop_file;
+
+	bh = sinfo.bh;
+	lock_buffer(bh);
+	memcpy(sinfo.de->name, label, sizeof(sinfo.de->name));
+	mark_buffer_dirty(bh);
+	unlock_buffer(bh);
+	err = sync_dirty_buffer(bh);
+	brelse(bh);
+	if (err)
+		goto out_drop_file;
+
+	memcpy(sbi->vol_label, label, sizeof(sbi->vol_label));
+
+out_drop_file:
+	mnt_drop_write_file(file);
+ out:
+	return err;
+}
+
 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
 	u32 __user *user_attr = (u32 __user *)arg;
+	u8 __user *user_vol_label = (u8 __user *)arg;
 
 	switch (cmd) {
 	case FAT_IOCTL_GET_ATTRIBUTES:
@@ -133,6 +245,10 @@ 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 FAT_IOCTL_GET_VOLUME_LABEL:
+		return fat_ioctl_get_volume_label(inode, user_vol_label);
+	case FAT_IOCTL_SET_VOLUME_LABEL:
+		return fat_ioctl_set_volume_label(filp, user_vol_label);
 	default:
 		return -ENOTTY;	/* Inappropriate ioctl for device */
 	}
-- 
2.11.0

Re: [PATCH v5 2/2] fs: fat: add ioctl method in fat filesystem driver

[OGAWA Hirofumi]

ChenGuanqiao <chen.chenchacha@foxmail.com> writes:

> +/* the characters in this field shall be d-characters, and unused byte shall be set to 0x20. */
> +static int fat_format_d_characters(char *label, unsigned long len)
> +{
> +	int i;
> +
> +	for (i=0; i<len; ++i) {
> +		switch (label[i]) {
> +		case '0' ... '9':
> +		case 'A' ... 'Z':
> +		case '_':
> +			continue;
> +		default:
> +			break;
> +		}
> +		break;
> +	}
> +
> + 	for (; i<len; ++i)
> +		label[i] = 0x20;
> +
> +	return len;
> +}

It should not accept and overwrite invalid char, return -EINVAL.

> +static int fat_ioctl_get_volume_label(struct inode *inode,
> +				      u8 __user *vol_label)
> +{
> +	int err = 0;
> +	struct fat_slot_info sinfo;
> +
> +	err = fat_scan_volume_label(inode, &sinfo);
> +	if (err)
> +		goto out;

It needs to take inode read lock.

> +	if (copy_to_user(vol_label, sinfo.de->name, MSDOS_NAME))
> +		err = -EFAULT;
> +
> +	brelse(sinfo.bh);
> +out:
> +	return err;
> +}
> +
> +static int fat_ioctl_set_volume_label(struct file *file,
> +				      u8 __user *vol_label)
> +{

[...]

> +	b = (struct fat_boot_sector *)bh->b_data;
> +
> +	lock_buffer(bh);

Probably, sb->s_umount to exclusive with remount update.

> +	if (sbi->fat_bits == 32)
> +		memcpy(b->fat32.vol_label, label, sizeof(label));
> +	else
> +		memcpy(b->fat16.vol_label, label, sizeof(label));
> +
> +	mark_buffer_dirty(bh);
> +	unlock_buffer(bh);
> +	err = sync_dirty_buffer(bh);
> +	brelse(bh);
> +	if (err)
> +		goto out_drop_file;

It should not update before preparing is done and checking error.

> +	/* updates root directory's vol_label */
> +	err = fat_scan_volume_label(inode, &sinfo);
> +	if (err)
> +		goto out_drop_file;

It should add entry if no volume label.

> +	lock_buffer(bh);

inode write lock.

> +	memcpy(sinfo.de->name, label, sizeof(sinfo.de->name));
> +	mark_buffer_dirty(bh);
> +	unlock_buffer(bh);

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>